היומן של milewski

(writing in progress)

Various mammals possess a caudal flag. This is defined as a pattern of dark and/or pale on the tail, in some cases extending to the adjacent rump or haunches, that is inconspicuous when the figure is stationary or at rest, but conspicuous when activated by movement.

Typical examples of caudal flags occur in

• Panthera pardus, as an example of an otherwise camouflage-coloured carnivore, and
• Odocoileus virginianus, as an example of a crytically-coloured herbivore.

'Porcupines' (https://en.wikipedia.org/wiki/Porcupine) are two families of rodents, namely Erethizontidae and Hystricidae, in which certain species have evolved extreme defences in the form of spines ().

In this Post I ask 'which of the 28 species of porcupines possess a caudal flag'?

The answer seems to be: only one species, namely Atherurus africanus. And this caudal flag is odd in that it is easily lost, during the lifetime of the individual, by means of autotomy.

https://ainawgsd.tumblr.com/post/181842995325/embed

https://www.agefotostock.com/age/en/details-photo/african-porcupine/FTF-R10000143/1

Before accounting in more detail for the adaptive value of a caudal flag in A. africanus, let us examine the tails of Hystrix africaeaustralis and H. indica. These are conspicuous enough to be candidates for a caudal flag, but probably do not qualify.

Trichys

https://www.ecologyasia.com/verts/mammals/long-tailed-porcupine.htm

Hystrix

https://www.alamy.com/stock-photo-indian-crested-porcupine-hystrix-indica-also-known-as-the-indian-porcupine-124427947.html

https://www.alamy.com/stock-photo-indian-crested-porcupine-hystrix-indica-also-known-as-the-indian-porcupine-124427951.html

(writing in progress)

In this Post, I define 'eye-mask' (https://en.wikipedia.org/wiki/Disruptive_eye_mask) as a dark feature of animal colouration that disguises the eyes, on a figure and head that are not dark overall.

This topic has recently started to appear in the scientific literature. See:

• https://en.wikipedia.org/wiki/Javan_slow_loris and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6409604/ and http://www.sitdowndisco.com/slow-loris-javan/ and https://www.optimistdaily.com/2020/10/a-network-of-suspended-bridges-are-helping-javas-slow-lorises-survive/,
• https://www.researchgate.net/publication/227522961_The_function_of_facial_masks_in_midguild_carnivores, and
• https://en.wikipedia.org/wiki/Norway_lemming and https://www.researchgate.net/publication/272412522_Aposematism_and_crypsis_in_a_rodent_antipredator_defence_of_the_Norwegian_lemming and https://www.alamy.com/norwegian-lemming-lemmus-lemmus-profile-troms-norway-image263197631.html.

I note that mammals possessing eye-masks tend to fall into two categories, viz.

• those with inconspicuous colouration overall, e.g. Otocyon megalotis (https://en.wikipedia.org/wiki/Bat-eared_fox#/media/File:Otocyon_megalotis_-_Etosha_2014.jpg) and Lycaon pictus (https://www.offset.com/photos/an-adult-african-wild-dog-lycaon-pictus-at-a-den-site-in-the-save-1003796 and https://www.offset.com/photos/wild-dog-lycaon-pictus-walking-371247) and Civettictis civetta (https://web.stanford.edu/~siegelr/animalz/civet.html and https://www.istockphoto.com/photo/afrcican-civet-gm1130101597-298779713 and Proteles cristatus (https://the-most-exteme.fandom.com/wiki/Aardwolf and https://animals.fandom.com/wiki/Aardwolf?file=Aardwolf.jpg) and
  Hyaena hyaena (https://www.shutterstock.com/nb/image-photo/adult-striped-hyena-hyaena-standing-open-1046826739 and https://thewesternghats.indiabiodiversity.org/observation/show/15098877?lang=en), and

• those with conspicuous enough overall patterns of dark/pale to be candidates for warning colouration, e.g. Mellivora capensis (https://www.sanbi.org/animal-of-the-week/honey-badger/ and https://naturerules1.fandom.com/wiki/Honey_Badger?file=47406105_303.jpg) and Gulo gulo (https://upload.wikimedia.org/wikipedia/commons/8/8c/Wolverine_on_rock.jpg) and Paraechinus aethiopicus (https://animals.fandom.com/wiki/Desert_Hedgehog?file=Ethiopian_Hedgehog_2_%2528Paraechinus_aethiopicus%2529-S.jpg and https://www.treknature.com/gallery/photo278073.htm) and Paraechinus micropus
  (https://eol.org/pages/1037265/media).

It makes sense that the eyes are particularly inconspicuous in animals that have overall colouration designed for hiding from prey, or from larger-bodied predators. However, any functional relationship between eye-masks and warning colouration remains to be explained.

As can be seen from the examples above, eye-masks in mammals occur mainly in predatory species. They are rare in plant-eating species.

However, a possible example is Erethizon dorsatum.

Is this plant-eater one of the few rodents to possess an eye-mask? And, if so, is this related to warning colouration in this 'porcupine'?

As far as I know, these possibilities have not previously been mooted in the literature.

Warning colouration in E. dorsatum is weaker and less consistent (see https://www.inaturalist.org/journal/milewski/65187-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-2#) than those in either African-Eurasian 'porcupines' (Hystrix) or the various genera of skunks (https://en.wikipedia.org/wiki/Skunk). The subtle dark/pale contrasts depend on posture and muscular movements of the skin in E. dorsatum. They are absent in some individuals, partly owing to seasonal and regional variation.

EVIDENCE OF EYE-MASK IN ERETHIZON DORSATUM

The following individuals of E. dorsatum seem to possess an eye-mask:

https://www.inaturalist.org/observations/8175871
https://www.inaturalist.org/observations/11274273
https://www.inaturalist.org/observations/10788818
https://www.inaturalist.org/observations/28411661
https://www.inaturalist.org/observations/37898442
https://www.inaturalist.org/observations/44542308
https://www.inaturalist.org/observations/33855151
https://www.inaturalist.org/observations/45805001
https://www.inaturalist.org/observations/80415227
https://www.inaturalist.org/observations/79231635
https://www.inaturalist.org/observations/78933797
https://www.inaturalist.org/observations/78111758
https://www.inaturalist.org/observations/77306649
https://www.inaturalist.org/observations/76953405
https://www.inaturalist.org/observations/69636688
https://www.inaturalist.org/observations/64210546
https://www.inaturalist.org/observations/27843255
https://www.inaturalist.org/observations/49303934
https://www.inaturalist.org/observations/47206486
https://www.agefotostock.com/age/en/details-photo/adult-male-north-american-porcupine-erethizon-dorsatum-minnesota-usa/YY4-1640900

However, the pattern is not clear-cut because, in some individuals in some seasons/regions,

• the whole face is darker than the rest of the figure, but without pale borders (https://www.inaturalist.org/observations/38528039 and https://www.inaturalist.org/observations/46195107 and https://www.inaturalist.org/observations/26640410 and https://www.inaturalist.org/observations/102256705 and https://www.inaturalist.org/observations/103290988 and https://www.shutterstock.com/nb/image-photo/north-american-porcupine-erethizon-dorsatum-walking-771903244 and https://www.istockphoto.com/photo/hiding-porcupine-gm613125744-105773153), or

• the main pattern is not an eye-mask but instead a pale patch centred on the crown and/or the area between the eye and the ear (https://www.inaturalist.org/observations/45076474 and https://www.inaturalist.org/observations/57911736
  https://www.inaturalist.org/observations/53602651 and https://www.istockphoto.com/photo/porcupine-foraging-on-new-spring-sprouts-gm1394970497-450247675), or

• the whole figure is dark (https://www.inaturalist.org/observations/103710257 and https://www.inaturalist.org/observations/108668820 and https://www.istockphoto.com/photo/north-american-porcupine-or-canadian-porcupine-or-common-porcupine-walking-gm515605852-88578399 and https://www.inaturalist.org/observations/106180206 and https://www.masterfile.com/image/en/600-03333549/north-american-porcupine-minnesota-usa and https://www.masterfile.com/image/en/600-03333550/north-american-porcupine-minnesota-usa).

Juveniles tend to be dark overall, lacking mask-colouration (https://www.istockphoto.com/photo/porcupines-gm180723145-24209220 and https://www.istockphoto.com/photo/baby-porcupine-gm157719814-22029118 and https://www.istockphoto.com/photo/baby-porcupine-gm504918032-83421755 and https://www.masterfile.com/image/en/841-03506138/a-captive-baby-porcupine-erethizon-dorsatum-animals-of and https://www.istockphoto.com/photo/baby-porcupine-gm174802022-22029114).

Some individuals are pale overall, for unknown reasons, e.g. https://www.researchgate.net/figure/An-isabelline-colored-North-American-Porcupine-Erethizon-dorsatum-from-Yukon-Canada_fig1_270904496 and https://www.inaturalist.org/observations/49305543 and https://www.istockphoto.com/photo/the-north-american-porcupine-also-known-as-the-canadian-porcupine-or-common-gm1272502547-374755167.

DISCUSSION

The anti-predator defences of Erethizon dorsatum are centred on its hindquarters, leaving the face relatively unprotected.

The carnivore most adept at killing E. dorsatum is Pekania pennanti (https://www.adfg.alaska.gov/index.cfm?adfg=fisher.printerfriendly#:~:text=Hunting%20Method,to%20descend%20trees%20head%20first). The relatively small body and elongated, weasel-like shape of this mustelid allow it to bypass the posterior spines and reach the front, whether the rodent is on the ground or climbing a tree. The carnivore thus manages to bite the face repeatedly until E. dorsatum is incapacitated.

Given that the face is, as it were, the Achilles' heel of E. dorsatum, and that most attacks occur by night, it may make sense that the rodent would benefit from its eyes being hidden. Furthermore, the inconsistency of the pattern may help to deny would-be predators - other than M. pennanti - a clear search-image in the first place.

A result of this obfuscation is that E. dorsatum is peculiarly non-photogenic even by day.

As any scrolling of the thousands of observations in iNaturalist soon shows (https://www.inaturalist.org/observations?taxon_id=44026), the photographed figure often looks almost faceless (e.g. https://www.alamy.com/close-up-portrait-of-a-porcupine-image439051825.html) unless the illumination is particularly clear.

@ludwig_muller

continued from https://www.inaturalist.org/journal/milewski/65447-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-3#

DISCUSSION

Hystrix is one of the few genera of plant-eating mammals on Earth that qualify as possibly possessing warning colouration at the scale of the whole body. Another, Lophiomys (https://en.wikipedia.org/wiki/Maned_rat), is toxic instead of spiny. In none of these genera is the overall pattern stark enough to qualify as warning colouration without the pelage being activated.

Erethizon qualifies for warning colouration only tenuously, because the pattern

• is only conspicuous once activated,
• is restricted to a smaller proportion of the body than in Hystrix, and
• is poorly-developed in certain individuals/regions/seasons.

The tail differs between Erethizon and Hystrix in various ways.

In Erethizon, the tail is large and used in posture and locomotion. On this basis it is unsurprising that it is also particularly important in anti-predator warning (conspicuous colouration https://www.inaturalist.org/observations/115828268, plus the sound of slapping) and defence (retaliatory striking to deploy caudal spines).

In Hystrix, the tail seems to play a negligible role in posture or locomotion. It may play an important role in deploying spines in H. brachyura and H. javanica.

However, in the other three species of Hystrix, the tail

• is conspicuous pale as is a minor component of the warning colouration of the whole figure (e.g. https://www.istockphoto.com/photo/crested-porcupine-hystrix-cristata-adult-back-view-gm1250684817-364854340), and
• makes warning sounds as an important component of the overall rattling of the pelage.

Overall, Erethizon emerges as the lineage with the greater emphasis on the adaptive value of the tail.

If we disregard the tail, 'porcupines' can perhaps be compared in various ways with the koala, sloths, and mole-rats.

Erethizon somewhat resembles the koala (https://en.wikipedia.org/wiki/Koala) in being able to survive on nutrient-poor, toxic leaves for months at a time (see http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=491 and https://news.uaf.edu/the-alaska-porcupines-winter-in-slow-motion/). However, the analogy is limited because Erethizon

• does so only after laying down large deposits of fat in autumn, and
• eats bark and cambium in winter, as an extremely fibrous nutrient-supplement.

Alternatively, Erethizon somewhat resembles sloths (https://en.wikipedia.org/wiki/Sloth), all the North American species of which were larger-bodied and have recently become extinct.

Erethizon differs from both the koala and sloths in the development of its incisors (https://www.naturshowroom.com/wp-content/uploads/2020/04/IMG_2105-rotated.jpg and https://www.inaturalist.org/observations/43961088).

Hystrix instead somewhat resembles mole-rats, despite the differences in body size.

Across its distribution in Africa and Eurasia, Hystrix coexists with many genera and species of mole-rats belonging to three families (https://en.wikipedia.org/wiki/Mole-rat). The North American counterparts are gophers (Geomyidae, https://en.wikipedia.org/wiki/Gopher).

Portrayal of Erethizon as an undersize ground-sloth and Hystrix as an oversize gopher is

• admittedly just caricature, and
• counter to the observation that it is Erethizon that, in most ways, looks more like a gopher.

However, this portrayal conveys some of the actual adaptive differences between these versions of 'porcupine'.

Approaching this discussion from a different perspective:

If a given species possesses extreme armour/weaponry, is this in addition to normal anti-predator adaptations, or instead of them?

To the degree that tortoises are typical of armoured animals, their slow-movement suggests that the answer may usually be 'instead of'.

How do Erethizon and Hystrix fit into this conceptual framework?

Erethizon seems below-par in the following normal adaptations:

• eyesight (unexpectedly small eyes),
• manual grip (poorly-developed pollex, limiting stability in climbing, and resulting in frequent injuries from falling out of trees),
• fleeing (limited ability to run, despite the legs being fairly long, https://www.inaturalist.org/observations/106180206 and https://www.inaturalist.org/observations/50808073),
• fecundity (one offspring per birth), and
• parental care (adults tend not to protect their offspring, even in the case of mothers).

This suggests that Erethizon relies largely on its spines - and the associated syndrome of warnings (including odour), body-orientation, and tail-wielding - for protection from predators. Such specialisation is noteworthy given that the unexcited animal looks fairly defenceless until it spreads the pelage around the particularly spiny rump.

In the case of Hystrix, the only adaptations that seem below-par are eyesight and braininess. The armour/weaponry is obvious even when the animal is unexcited, but the animals retain locomotory speed and, in their capacity to bear up to four offspring per year, considerable fecundity.

In explanation of this, there are differences in the predatory regimes (excluding Homo sapiens, https://natureconservation.pensoft.net/article/62750/).

Erethizon is vulnerable mainly to Pekania pennanti (https://en.wikipedia.org/wiki/Fisher_(animal) and https://www.arcticphoto.com/supergal/wl/wl01/wl0140-00.htm) and Puma concolor (https://en.wikipedia.org/wiki/Cougar).

By contrast, three of the species of Hystrix are vulnerable to a guild consisting of several coexisting species:

• Panthera leo and/or tigris (https://bioone.org/journals/journal-of-east-african-natural-history/volume-108/issue-1/028.108.0101/Lion-Porcupine-Interactions-in-Africa-Including-Impacts-on-Lion-Predatory/10.2982/028.108.0101.short
  and https://www.facebook.com/TourismFaceOfKarnataka/photos/a.570707786424475/1239352239560023/ and https://www.news18.com/news/india/maimed-by-porcupine-quills-tigress-stood-no-chance-against-dudhwa-mob-1931945.html and https://www.indiawilds.com/forums/showthread.php?2895-Tiger-Eating-Porcupine and https://timesofindia.indiatimes.com/city/bengaluru/tiger-hurt-in-fight-with-porcupine-found-dead/articleshow/56726421.cms and https://thelivenagpur.com/2019/12/30/tiger-freed-from-porcupine-quills-released-into-wild/ and https://timesofindia.indiatimes.com/city/nagpur/porcupine-quills-injure-tipeshwar-tiger-cub/articleshow/73021622.cms),

• Panthera pardus (https://roaring.earth/leopard-eats-porcupine-hyenas/ and https://www.facebook.com/bush24africa/posts/porcupine-vs-leopard-when-the-prey-fights-backporcupines-are-often-killed-by-leo/1486789681397890/ and https://www.youtube.com/watch?v=GYYwVfsk3q4 and https://www.flickr.com/photos/garyparker/6142977865 and https://www.ndtv.com/offbeat/watch-who-came-out-on-top-in-this-leopard-vs-porcupine-video-2231299),
• Mellivora capensis (https://www.earthtouchnews.com/natural-world/animal-behaviour/in-photos-honey-badger-feasts-on-a-porcupine/ and http://robinnicholsworkshops.blogspot.com/2013/09/the-trouble-with-honey-badgers.html),
• Parahyaena brunnea (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.664.8&rep=rep1&type=pdf) and Hyaena hyaena, and
• possibly Crocuta crocuta (https://ielc.libguides.com/sdzg/factsheets/spottedhyena/diet-feeding and http://con102.blogspot.com/2012/07/very-lucky-safari-family-or-not-good.html and https://www.youtube.com/watch?v=SmzvrkLNnvg).

Inasmuch as the predatory regime is particularly intense and diverse in the case of the African species, this may help to explain why Hystrix has retained relatively rapid locomotion and reproduction, in addition to its extreme armour/weaponry.

Several remarkable videos show Hystrix africaeaustralis defending itself against Panthera pardus. (Note that both the felid and the rodent possess whitish caudal flags.)

https://www.youtube.com/watch?v=gEYZl6gdDIE and https://www.dailymail.co.uk/embed/video/1272138.html and https://www.youtube.com/watch?v=dDtBYsSoMvU and https://www.youtube.com/watch?v=kmWs1FCkCxY and https://www.dailymail.co.uk/news/article-3481967/Ouch-did-Lioness-licks-wounds-getting-porcupine-quills-rear.html and https://www.dailymail.co.uk/news/article-9925091/A-prickly-customer-Leopard-left-quills-sticking-paws-hunting-porcupine.html and https://www.youtube.com/watch?v=kDFACDPDRqg and https://www.dailymail.co.uk/news/article-1248144/Young-leopard-gets-prickly-reception-tries-eat-porcupine.html and https://www.dailymail.co.uk/news/article-7430633/Leopard-bizarre-standoff-porcupine.html and https://www.dailymail.co.uk/news/article-2285373/Hell-feeling-prickly-Hungry-leopard-gets-spot-bother-trying-eat-porcupine.html and https://www.dailymail.co.uk/video/news/video-2488577/Video-Hungry-leopard-defeated-fearless-prickly-porcupine.html and https://www.youtube.com/watch?v=bBcnEhMfSho and https://www.huffpost.com/entry/leopard-porcupine-video_n_61f13217e4b0061af2586ab5 and https://www.facebook.com/watch/?v=2568431563219276 and https://www.mirror.co.uk/news/world-news/leopard-gets-prickly-reception-porcupine-5967709 and https://metro.co.uk/2010/02/03/leopard-has-a-prickly-moment-with-a-porcupine-73566/ and https://nypost.com/2015/03/23/hungry-leopard-takes-on-tough-porcupine-guess-who-won/ and https://www.earthtouchnews.com/natural-world/predator-vs-prey/claws-vs-quills-young-leopard-tries-its-luck-at-hunting-a-porcupine-video/ and https://www.independent.co.uk/news/world/africa/video-porcupine-takes-on-a-pride-of-17-lions-and-wins-9843974.html

The above include enough evidence from Kruger National Park, in particular, to suggest that nimble manoeuverability is essential to the anti-predator reactions of Hystrix.

Panthera pardus seems to find it relatively easy to kill H. africaeaustralis in culverts (cylindrical drains, made of concrete or metal, for stormwater, running under the road from one side to the other, https://www.gettyimages.ca/detail/news-photo/juvenile-spotted-hyena-cub-posing-in-front-of-den-entrance-news-photo/539279300?adppopup=true and https://somethingovertea.files.wordpress.com/2018/05/erosion6.jpg).

By contrast, when the encounter takes place on the surface of the road, the rodent seems relatively secure as long as it does not move off the open space.

I infer that H. africaeaustralis prefers the exposure of the road because it can keep orienting its body without obstruction. When in the culvert it is relatively constrained. It can fill the tunnel with the erect pelage while keeping its back to the predator. However, the felid can presumably snag the hindfeet by reaching forward at ground-level, thus knocking the rodent off its feet, in a way that would be impossible were the refuge a relatively narrow, natural burrow.

continued from https://www.inaturalist.org/journal/milewski/65187-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-2#

HABITAT

The latitudinal ranges of the two genera overlap at 28-41 degrees N.

This means that the southern part of the distribution of Erethizon, in northern Mexico and many states of the USA, is at similar latitudes to

• the northern part of the distribution of Hystrix indica in e.g. Turkey, Iran, Afghanistan, Azerbaijan, Turkmenistan, and Kyrgyzstan, and
• the southern part of the distribution of Hystrix africaeaustralis in most of South Africa.

Furthermore, both genera occur in a wide range of ecosystems from semi-desert (e.g. Erethizon in Nevada, https://www.birdandhike.com/Wildlife/Mamm/06Rod/09_Ereth/Erethi_dor/_Ere_dor.htm and https://www.fs.fed.us/psw/publications/zielinski/psw_2017_zielinski002_appel.pdf) to forest (e.g. Hystrix in Borneo, https://www.alamy.com/malayan-porcupine-hystrix-brachyura-acanthion-brachyura-walking-indonesia-image8113983.html and https://www.inaturalist.org/guide_taxa/178762).

However, the habitat of Erethizon is partly subarctic, whereas that of Hystrix is mainly tropical and subtropical.

In their zone of latitudinal overlap, Erethizon depends on woody vegetation (https://www.inaturalist.org/observations/13334310 and https://www.alamy.com/stock-photo-a-north-american-porcupine-walks-up-a-sand-dune-in-the-desert-177548000.html), whereas Hystrix does not (e.g. https://www.inaturalist.org/observations/104564486 and https://www.inaturalist.org/observations/103038302).

REPRODUCTION

Both Erethizon and Hystrix are long-lived in captivity (maximum lifespan 30 vs 28 years). However, the natural lifespan of Erethizon is effectively limited by the wear of its cheek-teeth to less than 10 years.

Both genera reproduce slowly, with usually one offspring per birth and per year. In both Erethizon and Hystrix, the newborns are precocial, with open eyes and some spines already formed.

However, Hystrix is more fecund than Erethizon. The former bears up to four offspring per birth and can breed twice per year (https://www.nature.com/articles/s41598-021-99819-3). Gestation is far shorter in Hystrix (90-112 days) than in Erethizon (205-217 days).

The extreme gestation of Erethizon
(https://www.degruyter.com/document/doi/10.1515/mamm.2001.65.1.73/html and https://www.jstor.org/stable/1375243) seems related to the extreme seasonality in the quality of its diet.

It is consistent with the extended gestation in Erethizon that the weight of the newborn relative to the mother (about 7%) exceeds that in Hystrix - even if the single neonate of the former is compared with a collective litter of two in the latter.

Unlike Erethizon and most other mammals, Hystrix tends to be monogamous (https://www.tandfonline.com/doi/pdf/10.1080/11250009709356189 and https://www.researchgate.net/publication/355180627_Reproductive_behaviour_in_free-ranging_crested_porcupine_Hystrix_cristata_L_1758 and https://www.degruyter.com/document/doi/10.1515/mamm.1991.55.2.187/html and https://www.sciencedirect.com/science/article/abs/pii/0018506X85900376), with paternal as well as maternal care.

FORAGING AND DIGESTION

Both Erethizon and Hystrix are basically terrestrial, which is unsurprising for such large-bodied rodents. However, they deviate from this in opposite ways. Erethizon is partly arboreal (https://www.dreamstime.com/porcupine-tree-close-up-portrait-deag-branch-image186080332) and seldom digs for food, whereas Hystrix cannot climb and is partly fossorial (https://en.wikipedia.org/wiki/Fossorial).

Both genera eat a wide variety of mainly plant matter, from cambium to fruits and roots. However, Erethizon depends mainly on woody plants and (particularly in winter, https://academic.oup.com/jmammal/article/92/3/601/867307?login=false and https://pubmed.ncbi.nlm.nih.gov/20306197/) foliage for its staples, whereas Hystrix depends mainly on herbaceous plants (particularly tubers such as bulbs and corms) and does not eat fibrous foliage.

Both genera have an enlarged caecum in which fermentation occurs (http://www.jafs.com.pl/Digestive-physiology-resting-metabolism-and-methane-production-of-captive-Indian,102741,0,2.html), and neither is caecotrophic or coprophagous. Their feces are similar (Erethizon https://www.inaturalist.org/observations/113658290 and Hystrix https://www.inaturalist.org/observations/93737688).

Digestion is extremely efficient in Erethizon despite:

• the fibrousness of its diet (https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1666&context=icwdm_usdanwrc), and
• the fact that neither it nor Hystrix eat their own feces (I suspect that Hystrix eats the feces of Hyaenidae in supplementation of calcium phosphate).

Both genera supplement their mineral nutrients by gnawing bones (https://www.istockphoto.com/photo/north-american-porcupine-erethizon-dorsatum-in-the-snow-near-haines-alaska-gm1266698735-371403945 and https://www.istockphoto.com/photo/porcupine-on-snow-with-moose-antler-and-birch-tree-in-winter-gm682855252-125266463 and https://www.yumpu.com/en/document/read/28237877/nutrition-of-the-north-american-porcupine-erethizon- and https://www.nature.com/articles/s41598-020-69252-z). Erethizon is well-known to seek out inorganic sources of sodium, which seems necessary owing to a seasonal excess of potassium to which Hystrix is not subject.

Both Erethizon and Hystrix hold food with their fore feet while eating.

However, a difference is that Erethizon, like most rodents, sits while doing so (https://www.istockphoto.com/photo/porcupine-gm490640318-75310819 and https://www.istockphoto.com/photo/north-american-porcupine-also-known-as-canadian-porcupine-or-common-porcupine-is-a-gm1391478903-448081294), whereas Hystrix keeps the forelegs on the ground (https://www.youtube.com/watch?v=8Q3TiLfH504 and https://www.alamy.com/porcupine-the-prickliest-of-rodents-though-its-latin-name-means-quill-pig-image179580322.html).

The lack of a sitting or squatting posture in Hystrix is possibly owing to the obstruction by long spines on the rump.

SOCIAL BEHAVIOUR

Erethizon shows minimal social behaviour. By contrast, Hystrix is not only monogamous but also somewhat gregarious in its underground refuges (https://animaldiversity.org/accounts/Hystrix_cristata/ and https://rep.bioscientifica.com/configurable/content/journals$002frep$002f92$002f1$002fjrf_92_1_004.xml?t:ac=journals%24002frep%24002f92%24002f1%24002fjrf_92_1_004.xml).

Both genera tend to be noisy in normal activity. Erethizon is by far the more vocal (e.g. https://www.inaturalist.org/observations/16521684 and https://www.inaturalist.org/observations/48843732 and https://www.inaturalist.org/observations/42157159). However, Hystrix snuffles loudly, and sometimes grunts, during foraging.

In most species of mammals, male offspring are more likely than female offspring to move far from the parental location. Erethizon is unusual in that it is the females that leave (https://sites.warnercnr.colostate.edu/wp-content/uploads/sites/30/2017/11/1998-Sweitzer-Berger-evidence_for_femalebiased_dispersal_in_north_american_porcupines_erethizon_dorsatum.pdf and https://www.jstor.org/stable/41717257).

to be continued...

continued from https://www.inaturalist.org/journal/milewski/65099-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-1#

COLOURATION

The colouration of both Erethizon and Hystrix combines

• dark/pale contrast sufficient to accentuate, even at night, the conspicuousness of the displaying animal (particularly the tail) and its individual spines (https://www.inaturalist.org/observations/80776828 and https://www.inaturalist.org/observations/115015707 and https://www.alamy.com/stock-photo-a-lioness-and-porcupine-encounter-buffelshoek-mpumalanga-south-africa-11770986.html and https://www.dreamstime.com/royalty-free-stock-photo-porcupine-quills-image18098955), and
• a pattern subtle enough to function as camouflage if the figure stands still, with the pelage relaxed, in apprehension at the approach of a potential predator (https://www.pixcove.com/canadian-porcupine-canada-porcupine-animal-physical-prickly-spur-touchy/).

Erethizon differs from Hystrix in that, in the winter coat, the pale surfaces of the spines themselves are generally invisible on the body of the relaxed or normally active figure, being covered by long non-spiny hairs (https://www.agefotostock.com/age/en/details-photo/north-american-porcupine-erethizon-dorsatum-in-a-creek-bed-canadian-porcupine-common-porcupine-donjek-route-kluane-national-park-st/IBK-990718 and https://www.zoobasel.ch/en/aktuelles/news/1324/neu-im-zoo-basel-zu-sehen-ursons/).

The colouration of Erethizon is more variable individually, seasonally, and regionally, than that of Hystrix.

However, in Erethizon

• there is often a dark/pale contrast on the tail (https://www.inaturalist.org/observations/79233978 and https://www.youtube.com/watch?v=Cuq2ouHc76M and https://www.youtube.com/watch?v=YjvN0NNCQ_4 and https://www.facebook.com/watch/live/?ref=watch_permalink&v=1272811696508002) even in the winter coat (https://www.inaturalist.org/observations/111270691), and
• the winter coat can be dark overall, potentially making the whole figure conspicuous against the pale backgrounds of the cold season in North America (compare https://www.facebook.com/watch/?v=2046841385585189 and https://www.dreamstime.com/stock-photo-old-male-porcupine-walking-snow-winter-image42454922 and https://www.istockphoto.com/photo/porcupine-on-a-snowy-stroll-gm1287351189-383586334 and https://www.dreamstime.com/porcupine-winter-close-up-prairie-saskatchewan-canada-image215015453 with https://www.alamy.com/porcupine-quills-denali-national-park-alaska-image213864011.html).

In Hystrix, the tail is conspicuously pale, but only in

• H. africaeaustralis (https://www.inaturalist.org/observations/38952943 and https://www.inaturalist.org/observations/62727813 and https://www.inaturalist.org/observations/38953927 and https://www.inaturalist.org/observations/68484973 and https://www.inaturalist.org/observations/21203686 and https://www.inaturalist.org/observations/10875286 and https://www.inaturalist.org/observations/27937181), and
• H. indica (https://www.inaturalist.org/observations/44362166 and https://www.inaturalist.org/observations/11107349).

ANTI-PREDATOR DEFENCES

Both Erethizon and Hystrix base their anti-predator defences on barbed spines, which are much-thickened, fortified hairs with pithy (spongy) interiors (https://animaldiversity.org/collections/spinesquills/ and https://books.google.com.au/books?id=A3HuW_DMglQC&pg=PA17&lpg=PA17&dq=Fluorescence+of+porcupine+quills&source=bl&ots=6LnVvz0tS4&sig=ACfU3U07ghTW_RF0PEOYmHq9jQ1Bo6_PgQ&hl=en&sa=X&ved=2ahUKEwjUqbj3nMf3AhWWzDgGHTQHAmQ4ChDoAXoECCcQAw#v=onepage&q=Fluorescence%20of%20porcupine%20quills&f=false).

The spines not only pierce the skin of attackers, but detach easily from the source.

This leaves the spines firmly embedded and able to work their way, by virtue of the automatic/passive ratchet-mechanism of the barbs, either

• perpendicularly, deeper into the body with the risk of penetrating internal organs, and/or
• laterally and subcutaneously, parallel to the surface of the body.

See https://www.lichenlabs.net/product/porcupine-quill-cholla-cactus-spines/ and https://www.researchgate.net/figure/SEM-images-of-the-structure-of-the-Erethizon-quill-a-entire-morphology-in-transverse_fig4_230863177 and https://www.discovermagazine.com/planet-earth/why-porcupine-quills-slide-in-with-ease-but-come-out-with-difficulty and https://www.science.org/content/article/porcupine-quills-reveal-their-prickly-secrets and https://www.sciencephoto.com/media/107817/view/porcupine-quill-sem and https://www.npr.org/sections/health-shots/2019/04/09/711050307/porcupine-barbs-for-better-wound-healing and https://www.nbcnews.com/tech/tech-news/point-porcupines-inspired-improved-surgical-tape-flna1c7529221 and https://www.nature.com/news/barbs-make-porcupine-quills-into-nasty-needles-1.11986 and https://repository.up.ac.za/handle/2263/15216?show=full.

The two genera differ in:

• the length of the longest spines: up to 7.5 cm in Erethizon vs up to 30 cm in Hystrix, and
• the extent of spininess in the pelage: covering much of the body plus the crown in Erethizon, vs restricted to the back and hindquarters in Hystrix.

The following show the shortness of the spines of Erethizon:
https://www.inaturalist.org/observations/116397549 and https://www.inaturalist.org/observations/69200459 and https://www.inaturalist.org/observations/19849435 andhttps://www.featheredphotography.com/blog/2018/09/12/why-a-snoot-full-of-porcupine-quills-can-be-a-serious-matter/ and https://lmtribune.com/outdoors/porcupine-pointer-pain/article_3c62ccb8-c8cf-5867-a747-e225e0539781.html and https://www.cbc.ca/news/canada/edmonton/porcupine-quills-dog-attack-1.4594566 and https://kdvr.com/news/dog-that-had-encounter-with-porcupine-continues-to-recover-after-three-hour-surgery/ and https://www.petful.com/pet-health/porcupine-attacks-on-dogs/.

The following show the lengths of the spines of several species of Hystrix:
https://www.wildcard.co.za/krugers-daring-leopards-match-porcupines/ and https://www.youtube.com/watch?v=9Qr1LVaEysk and https://www.mensjournal.com/adventure/leopard-attacked-by-porcupine-suffers-painful-hunting-lesson/ and https://www.wildcard.co.za/krugers-daring-leopards-match-porcupines/ and https://www.dailymail.co.uk/news/article-3323494/He-REALLY-didn-t-think-one-Red-faced-leopard-looks-ready-throw-furious-fight-porcupine-ends-face-quills.html and https://www.dailymail.co.uk/news/article-2945715/Don-t-pick-nose-Lion-cub-gets-porcupine-s-quill-stuck-nostril-trying-eat-s-worse-ending-porcupine-cat-s-dad-turns-up.html and https://www.inaturalist.org/observations/102469650 and https://www.alamy.com/stock-photo-lion-cub-investiging-porcupine-87078362.html and https://owenslaterphotography.com/2016/12/02/honey-badger-vs-crested-porcupine/ and https://www.nationalgeographic.com/animals/article/lions-hunt-porcupines-human-impact.

When predators eat Erethizon, they discard the whole skin (https://www.inaturalist.org/observations/74560373). In the case of Hystrix, only the pelage itself is discarded, the skin apparently being eaten.

In both genera, the defensive syndrome is accentuated by

• erection of the pelage (including guard hairs) around the spiny rump, by means of a combination of pilo-erection and larger-scale contraction of subcutaneous muscles (https://www.inaturalist.org/observations/112229589 and https://cosmosmagazine.com/nature/animals/lions-attack-porcupines-porcupine-wins/ and https://www.pictorem.com/79030/Porcupine%20(Erethizon%20Dorsatum)%20Crossing%20A%20Trail,%20Forillon%20National%20Park;%20Quebec,%20Canada.html and https://www.marylandbiodiversity.com/view/808 and http://www.adfg.alaska.gov/index.cfm?adfg=northamericanporcupine.photogallery&number=6 and https://www.shutterstock.com/nb/image-photo/porcupine-opens-back-spines-react-1464597659 and https://www.alamy.com/stock-photo-lion-cub-investiging-porcupine-87078361.html), which exaggerates body size,
• production of various ominous sounds, and
• turning the particularly spiny posterior towards, and striking backwards/sideways at, the potential predator.

However, Erethizon and Hystrix differ in several ways, as follows.

Erethizon seems not to strike until the pelage is touched, whereas Hystrix attempts to strike preemptively once the potential predator approaches closely. Erethizon thus tends to strike as retaliation, whereas Hystrix tends to strike as intimidation. This is consistent with

• the visual display being starker in Hystrix than in Erethizon, and
• the defensive display being in a sitting posture in Erethizon vs a standing posture in Hystrix.

Both Erethizon and Hystrix have a large patch of spines on the rump, lacking guard hairs, that is exposed by the erection of the surrounding long pelage. In this rump-patch the spines (which are short in both genera) have mixed orientations (https://www.alamy.com/a-young-north-america-porcupine-erethizon-dorsatum-raises-the-quills-on-its-back-in-a-threat-display-upper-clements-annapolis-royal-nova-scotia-image246934252.html and https://www.alamy.com/north-america-united-states-alaska-denali-national-park-wildlife-porcupine-erethizon-dorsatum-spring-defensive-quills-up-image384814685.html and https://www.inaturalist.org/observations/96103364 and https://www.inaturalist.org/observations/35185393 and https://www.inaturalist.org/observations/8397945 and https://www.inaturalist.org/observations/21385210 and https://www.inaturalist.org/observations/92557550 and https://www.inaturalist.org/observations/6183394 and https://www.inaturalist.org/observations/3779300).

Only Erethizon uses odour as part of the defensive repertoire, compensating for the limited conspicuousness of the relatively short spines (https://www.researchgate.net/publication/227058437_Warning_Odor_of_the_North_American_PorcupineErethizon_dorsatum).

This odour is secreted from the otherwise bare-skinned patch of dark spines on the back/rump, and is facilitated by a wick effect of these spines themselves (https://books.google.com.au/books?id=A3HuW_DMglQC&pg=PA17&lpg=PA17&dq=Fluorescence+of+porcupine+quills&source=bl&ots=6LnVvz0tS4&sig=ACfU3U07ghTW_RF0PEOYmHq9jQ1Bo6_PgQ&hl=en&sa=X&ved=2ahUKEwjUqbj3nMf3AhWWzDgGHTQHAmQ4ChDoAXoECCcQAw#v=onepage&q=Fluorescence%20of%20porcupine%20quills&f=false and https://www.dreamstime.com/stock-photo-close-up-prickly-porcupine-northern-british-columbia-wildlife-as-seen-hike-canadian-forest-image57706727 and https://www.dreamstime.com/porcupine-photo-stock-close-up-profile-view-walking-gravel-side-road-foliage-foreground-rock-background-image219969435).

The release of the defensive odour is accompanied by a second stage in the activation of the pelage of the rump. In the first stage, what is displayed is a patch of mainly whitish spines. In the second stage, the tone changes to dark, and the warning changes from visual to olfactory.

Only Hystrix uses pilo-erection of long hairs other than guard hairs or spines to exaggerate its body size as part of the defensive display. This produces a 'nuchal crest' (https://www.robertharding.com/preview/743-880/porcupine-hystrix-africaeaustralis-limpopo-south-africa-africa/ and https://www.youtube.com/watch?v=EeZW3UcW1Yc and https://www.shutterstock.com/nb/image-photo/cape-porcupine-south-african-hystrix-africaeaustralis-1304830168 and https://wellcomecollection.org/works/dj2bhb4u/items and https://wildkratts.fandom.com/wiki/African_Crested_Porcupine?file=African+Crested+Porcupine.PNG and https://www.istockphoto.com/photo/porcupine-is-eating-in-namibia-africa-gm619090370-107922591).

In Erethizon, the guard hairs on the crown and nape can be long (https://www.inaturalist.org/observations/111701471 and https://www.alamy.com/north-american-porcupine-alberta-canada-image66233270.html), but there seems to be no particular display of these as part of the anti-predator reactions. Furthermore, the crown and nape - like the rest of the forequarters - are spiny in Erethizon (https://www.inaturalist.org/observations/40158394 and https://www.inaturalist.org/observations/45858048 and https://www.inaturalist.org/observations/45193401) while lacking spines in Hystrix.

In both genera, the tail bears erectile spines and can have warning colouration:

• Erethizon (https://www.inaturalist.org/observations/27125781 and https://www.inaturalist.org/observations/52947754 and https://www.dreamstime.com/stock-photo-close-up-prickly-porcupine-northern-british-columbia-wildlife-as-seen-hike-canadian-forest-image57706759 and https://www.dreamstime.com/stock-photo-north-american-porcupine-close-up-image-image95224115), and
• Hystrix (https://www.shutterstock.com/nb/image-photo/crested-porcupine-photographed-back-spikey-1829516969 and https://www.shutterstock.com/nb/image-photo/crested-porcupine-hystrix-cristata-adult-back-1646445505).

However, in Erethizon the tail is proportionately large and muscular enough to be wielded as a flexible, fast-moving, spine-embedding organ, and its colouration tends to contrast dark on the upper and lower surfaces with pale on the sides (https://www.robertharding.com/preview/764-609/porcupine-erethizon-dorsatum-mother-baby-captivity-sandstone-minnesota/). In Hystrix the whole tail tends to be conspicuously pale in two of the species (see above). This is fully exposed to view once the long pelage around the rump-patch is erected in the warning reaction (https://www.shutterstock.com/nb/image-photo/crested-porcupine-hystrix-cristata-adult-1646445481).

In Hystrix a main function of the tail (but restricted to certain species) is production of a warning sound - namely a hiss-like rattling - by means of specialised caudal quills. These are broad, hollow, and whitish, but blunt and harmless; in their full development they may have narrow, flexible stalks.

Both genera thus use percussion as part of their defensive repertoire.

However,

• Erethizon clacks the incisors (https://www.inaturalist.org/observations/75603980) and chatters the cheek-teeth (mainly in males), and slaps the tail on the ground, whereas
• Hystrix rattles the pelage (particularly the specialised caudal quills), grunts, and stamps the feet.

to be continued...

@kevinatbrakputs @karoopixie @alexanderr @maxallen @caraleigh @danavan @jwidness @ken_j_allison @edporopat @arborsphere @whutchins @swampy @jnstuart @e-aus-kanada @nsharp @alwoodhouse @saber_animal @jakob @ariel-shamir @gwark @jonpoppele @alanmuchlinski @bartwursten @markusgmeiner @christiaan_viljoen @markuslilje @opisska @ockertvs @lovecamp @asio-otus @lynnharper @birderryan @astanyoung @fatroosterfarm @miscelaineous @pfau_tarleton @donaldmcleod @pinawapt @jerry_deboer @douglasriverside @nvpyromelana @colincroft @jasonheadley @alexlamoreaux @aterrigeol @zonotrick @cindychrisler @tmurray74 @mlodinow @ungerlord @michael_oldham @icbryson @desmond_macneal @camerondeckert @scottranger @justinhawthorne @jujurenoult @er1kksen @davidrscott @katzyna @ksled @dan_macneal @md-in-ns15 @mnerrie @dlcoleman @arcticory @nn4ever @codystricker @baywren @bert_raccoon @mikehannisian @meganhanson @amzapp @janeyd @mc1991 @josh_vandermeulen @mahu99 @zaccota @creedo @howlin_jay @erwinsieben @nyoni-pete @dewald2 @marco_vicariotto @emilianomori @ryruther @benjamynweil @ivanovdg19 @vmoser @natemartineau @lucaboscain

(Many thanks to Kim Cabrera @beartracker for information useful in this series of Posts.)

Among the various mammals that defend themselves by means of spines, 'porcupines'

• are the largest-bodied forms (https://www.adn.com/alaska-news/science/2022/01/08/how-do-stagnant-bark-nibbling-porcupines-survive-frigid-alaska-winters/ and https://www.thedodo.com/bottle-fed-porcupine-returns-to-her-rescuers-1896274948.html),

• have the most extreme forms of spines (https://www.naturalhistorymag.com/htmlsite/master.html?https://www.naturalhistorymag.com/htmlsite/0306/0306_feature.html and http://hotcore.info/babki/Porcupine-Quills-In-Dogs.html and
  https://www.youtube.com/watch?v=ZphlCdI2yqA and https://www.jstor.org/stable/1383565)
  and https://www.researchgate.net/publication/229674283_Mechanical_design_of_hedgehog_spines_and_porcupine_quills and https://www.researchgate.net/publication/341999648_Microstructure_of_Quills_in_Sunda_Porcupine_Hystrix_javanica_F_Cuvier_1823_Mikrostruktur_Duri_Landak_Jawa_Hystrix_javanica#:~:text=Nutritional%20content%20of%20the%20quills%20were%20water%20(89.93%25)%2C%20crude,sulphur%20(2%2C01%25),

• possess spines even as infants (https://people.com/pets/baby-porcupine-born-in-front-of-guests-at-london-zoo/ and https://www.inaturalist.org/observations/102620880 and https://www.shutterstock.com/nb/image-photo/indian-crested-porcupine-baby-on-white-1038376888 and https://www.shutterstock.com/nb/image-photo/crested-porcupine-hystrix-cristata-female-young-1645995043),
• have warning colouration on both spines and other parts of the pelage (https://www.inaturalist.org/observations/46932604 and https://www.inaturalist.org/observations/89417614 and https://www.inaturalist.org/observations/80829627 and https://www.inaturalist.org/observations/80453530 and https://www.youtube.com/watch?v=woYjHBgm7oI), and
• have behaviours warning potential predators of the spiny defence, and retaliating to approach or contact with the well-developed guard hairs (for Erethizon, see https://www.alamy.com/porcupine-walking-through-a-the-summer-meadow-in-canada-image370342694.html and https://alaskafurid.wordpress.com/2009/11/02/porcupine/ and https://www.youtube.com/watch?v=-lgUmbhQ9vo and https://www.youtube.com/watch?v=cZ3UFsOlprI and https://www.youtube.com/watch?v=Z5iBzykfJko and https://www.youtube.com/watch?v=d28I9s6lpOY; for Hystrix see https://www.alamy.com/stock-photo-cutout-image-of-2-porcupine-quills-against-a-white-background-31305577.html).

However, the term 'porcupine' conflates two different lineages of rodents (https://animals.sandiegozoo.org/animals/porcupine). While these are similar enough to be confused in the public mind, they also differ significantly.

TAXONOMY

Any comparison is complicated by the fact that

• there is only one species in Erethizon (https://academic.oup.com/mspecies/article/doi/10.2307/3504036/2600610?login=false and https://www3.uwsp.edu/biology/VertebrateCollection/Pages/Vertebrates/Mammals%20of%20Wisconsin/Erethizon%20dorsatum/Erethizon%20dorsatum.aspx#:~:text=Quills%20are%20modified%20guard%20hairs,pointing%20barbs%20(Roze%201989).
  and https://www.chesapeakebay.net/discover/field-guide/entry/north_american_porcupine and http://www.adfg.alaska.gov/index.cfm?adfg=northamericanporcupine.video and https://www.turtlebay.org/north-american-porcupine and https://nhpbs.org/natureworks/porcupine.htm and https://animalsofpnw.com/2021/08/05/porcupines-of-the-pacific-northwest/), vs

• five relevant species in Hystrix (excluding subgenus Thecurus, which is restricted to several islands in southeast Asia).

However, I treat collectively the five species of Hystrix, namely

• H. indica (mainland Asia, https://larastock.com/deposit-photo-221778628/?url=search/hystricomorph/ and https://www.istockphoto.com/photo/indian-crested-porcupine-on-grass-gm513787305-47371684 and https://rajajinationalpark.org/indian-crested-porcupine/ and https://www.projectnoah.org/spottings/1705106005/fullscreen and https://www.youtube.com/watch?v=Mk2RxZDb360 and https://www.tierpark-berlin.de/en/animals/indian-crested-porcupine and https://stock.adobe.com/search?k=%22indian+porcupine%22&asset_id=199150230),
• H. cristata (northern half of Africa plus Italy, https://escholarship.org/content/qt2tk1m81s/qt2tk1m81s_noSplash_3d0b3d6a295711913883e0eb5d1fe818.pdf?t=r1k9ob and https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/az2010n2a2.pdf and https://www.mindenpictures.com/stock-photo-crested-porcupine-hystrix-cristata-foraging-on-ground-central-kenya-naturephotography-image90199652.html and https://www.shutterstock.com/nb/image-photo/porcupine-wildlife-africa-walking-around-thousand-142715425),
• H. africaeaustralis (southern half of Africa, https://www.sanbi.org/animal-of-the-week/cape-porcupine/ and https://www.inaturalist.org/observations/109172672 and https://focusedcollection.com/238091908/stock-photo-closeup-view-portrait-porcupine-running.html and https://www.alamy.com/stock-photo-cape-porcupine-or-south-african-porcupine-hystrix-africaeaustralis-24156097.html),
• H. brachyura (southeast Asia, https://upload.wikimedia.org/wikipedia/commons/5/54/Hystrix_brachyura%2C_Malayan_porcupine.jpg and https://www.shutterstock.com/nb/image-photo/profile-view-himalayan-porcupine-malayan-crested-2090406331 and https://www.shutterstock.com/nb/image-photo/malayan-porcupine-himalayan-large-porcupinehystrix-brachyura-525835324 and https://www.inaturalist.org/guide_taxa/999419 and https://www.ecologyasia.com/verts/mammals/malayan-porcupine.htm and https://naturerules1.fandom.com/wiki/Malayan_Porcupine?file=Malayan_Porcupine.jpg), and
• H. javanica (Indonesia, https://agris.fao.org/agris-search/search.do?recordID=DJ20210670575 and file:///C:/Users/Antoni%20Milewski/Downloads/3630-Article%20Text-6252-1-10-20190301.pdf and https://observation.org/photos/1414727/ and https://www.alamy.com/malayan-porcupine-in-cave-at-pangandaran-java-indonesia-image221010859.html and https://indonesiawindow.com/en/dozens-of-javanese-porcupines-return-to-natural-habitat/).

BODY SIZE and FORM

Erethizon and Hystrix overlap broadly in body mass, in the range 6-13 kg. However, the former is smaller-bodied than the latter.

Erethizon weighs as little as 3.5 kg when adult and lean, whereas Hystrix weighs as much as 25 kg. The heaviest, fattest specimens recorded for the two genera are 18 kg vs 27 kg.

In Erethizon, males outsize females; in Hystrix, the sexes have similar body size (https://www.tandfonline.com/doi/abs/10.1080/11250008709355592).

In https://www.youtube.com/watch?v=w4NfE9mqU64, the individual of Panthera pardus is an adult male, probably weighing more than 55 kg. By comparison, this individual of Hystrix africaeaustralis - as likely female as male - may weigh as much as 25 kg.

Both genera have small eyes (https://stock.adobe.com/sk/search/images?k=porcupine+face&asset_id=480402738 and https://stock.adobe.com/sk/search/images?k=porcupine+face&asset_id=175434829 and https://www.istockphoto.com/photo/crested-porcupine-gm90848177-2184836) and the same dental formula. However, the skulls differ surprisingly. That of Erethizon (https://animaldiversity.org/collections/contributors/skulls/erethizon/e._dorsatum/87345.lateral/) is unremarkable among rodents. By contrast, that of Hystrix (https://www.inaturalist.org/observations/36773744 and https://www.inaturalist.org/observations/17389159 and https://animaldiversity.org/collections/contributors/phil_myers/ADW_mammals/specimens/Rodentia/Hystricidae/Hystrix_indica/lateral6337/) has extremely inflated nasal and frontal bones.

The cranium also seem to differ in relative size. If Erethizon is brainier than Hystrix, this would be consistent with its play behaviour in adulthood (https://psycnet.apa.org/record/1944-03113-001) and its performance in memorising mazes (https://psycnet.apa.org/record/2005-14412-004).

The tail is proportionately larger in Erethizon (https://www.sciencephoto.com/media/1009962/view/north-american-porcupine-skeleton and https://fineartamerica.com/featured/1-north-american-porcupine-skeleton-millard-h-sharp.html and https://www.istockphoto.com/photo/north-american-porcupine-on-a-branch-gm519080646-90356241) than in Hystrix (https://paolov.files.wordpress.com/2015/03/20140227_143245.jpg and https://www.alamy.com/porcupine-skeleton-in-profile-view-after-antique-engraving-from-the-19th-century-image434355969.html).

POSTURES and LOCOMOTION

Both genera use the same gait in walking.

Erethizon:
https://www.inaturalist.org/observations/26949994 and https://www.shutterstock.com/nb/video/clip-2870482-north-american-porcupine-erethizon-dorsatum-walking-along and https://www.youtube.com/watch?v=cnos437-t18 and https://www.inaturalist.org/observations/95054372 and https://www.pond5.com/stock-footage/item/12263333-north-american-porcupine-walking-along-road-leaf-stuck-its-f.

Hystrix:
https://www.istockphoto.com/photo/porcupine-walking-gm177703348-24110328 and https://www.youtube.com/watch?v=5nbaSyg3Z1M.

Both genera prefer to commute along pathways, and Erethizon depends on creating its own pathways when commuting across deep snow.

The tracks of Erethizon (https://www.bear-tracker.com/porcpine.html) and Hystrix (https://twitter.com/bgsurvival/status/731435193278566400) are similar. In both genera, the feet are usually pointed somewhat inward in the walking gait.

However, the forefeet of the two genera differ. In Erethizon (https://natureidentification.com/how-to-identify-porcupine-erethizon-dorsatum-tracks/), the claws are long, the bare surface is rough, and the pollex is present, albeit only as a clawless pad. These features differ from Hystrix (https://www.natureinstock.com/search/preview/cape-porcupine-hystrix-africaeaustralis-adult-close-up-of-front-foot/0_11296644.html and https://www.inaturalist.org/observations/19891886).

Both Erethizon and Hystrix are able to swim (https://www.researchgate.net/publication/330451642_Behaviour_of_a_porcupine_Erethizon_dorsatum_swimming_across_a_small_boreal_stream and https://www.youtube.com/watch?v=wt1PMbVnB44). Neither genus seems capable of jumping.

However, postures and locomotion differ between the two genera in important ways.

Erethizon differs categorically from Hystrix in adopting the following postures/gaits, all of which use the muscular tail as a prop:

• sitting, which includes a hunched posture typical of the initial reaction to the approach of a potential predator (https://www.inaturalist.org/observations/14860384 and https://www.alamy.com/porcupine-standing-in-a-summer-meadow-in-canada-image370342894.html and https://www.peninsulaclarion.com/sports/the-porcupine-an-underappreciated-creature/ and https://www.dreamstime.com/porcupine-posing-his-hind-legs-spiky-porcupine-posing-his-hind-legs-giving-friendly-porcupine-smile-image128446819),
• standing and even walking bipedally (https://www.istockphoto.com/photo/north-american-porcupine-standing-on-hind-legs-erethizon-dorsatum-also-known-as-gm823905994-133351179 and https://www.vicnews.com/home2/photo-porcupine-taking-a-stroll-in-the-yukon-turns-heads/), for example during courtship, and
• climbing vertically (both upwards and downwards) by means of a gait in which the forelegs are extended in unison, with the hindlimbs moving subsequently in unison (https://www.youtube.com/watch?v=fXr7S3MbAaE and https://www.youtube.com/watch?v=w7R-GAUFqTg and https://www.inaturalist.org/observations/109799198).

Erethizon is capable of hanging upside down from branches (https://natlands.org/porcupines/ and https://www.istockphoto.com/photo/north-american-porcupine-gm1285939555-382593958), but cannot locomote while doing so.

By contrast, Hystrix climbs so poorly that adults can reputedly be kept captive by walls only one metre high.

Neither Erethizon nor Hystrix has spines on the ventral surfaces. However, in Erethizon the bristly hairs here - particularly on the ventral surface of the tail - enhance friction during climbing, compensating partly for the poor development of the pollex (https://www.inaturalist.org/observations/112849002 and https://www.shutterstock.com/nb/image-photo/north-american-porcupine-erethizon-dorsatum-on-310015790 and https://www.adfg.alaska.gov/index.cfm?adfg=northamericanporcupine.main).

Erethizon seems hardly able to run (https://www.youtube.com/watch?v=4v-XGIi0O4s and https://www.shutterstock.com/nb/image-photo/porcupine-running-thru-winter-snow-colville-108288905 and https://www.alamy.com/adult-north-american-porcupine-erethizon-dorsatum-running-in-glacier-bay-national-park-alaska-united-states-of-america-north-america-image417695139.html).

Hystrix is slow-moving relative to ungulates, but is versatile in its terrestrial gaits, as follows:

• it is capable of fleeing by trotting and cantering/galloping (https://www.youtube.com/watch?v=jl8nAJCKRUY and https://www.youtube.com/watch?v=tZnGBWB2Yew and https://www.shutterstock.com/nb/image-photo/crested-porcupine-running-across-meadow-1806708133 and https://www.youtube.com/watch?v=Blhyrwgq3j0 and https://www.youtube.com/watch?v=QVhTR9PGvSU), and
• its limb movements are rapid during the intermittent walking used in standoffs with potential predators; this defensive locomotion is forwards, backwards, and sideways according to the manoeuvres of the predator, so as to keep the longest spines and guard hairs pointed at the danger while repelling any close approach.

to be continued...

continuing from https://www.inaturalist.org/journal/milewski/64019-why-has-there-never-been-a-donkey-size-jackrabbit-part-1#

SPECIALISATION IN POSTURE

Hares have a postural and locomotory syndrome in which:

• the stationary figure squats (https://www.alamy.com/stock-photo-black-tailed-jackrabbit-lepus-californicus-at-the-palo-alto-baylands-17292053.html) instead of standing or sitting,
• the foraging figure crouches (https://www.alamy.com/stock-photo-skeleton-of-a-european-brown-hare-lepus-europaeus-50017637.html and https://www.alamy.com/black-tailed-jackrabbit-juvenile-lying-down-with-ears-folded-down-and-hiding-in-alert-santa-clara-county-california-usa-image463190925.html) instead of bending the neck deeply,
• the foraging or commuting figure uses bound-walking (https://www.youtube.com/watch?v=WkGS4NJwTUk) as a gait allowing slow and intermittent locomotion in crouched form, instead of the amble or cross-walk normal for terrestrial mammals,
• the vigilant figure is bipedal with erection of the long, flexible ear pinnae in compensation for the limited length of the neck, and
• the fleeing figure is able to gallop extremely rapidly by virtue of full extension of the limbs and flexure of the spine (https://www.youtube.com/watch?v=RthDHV9KAbY).

The more massive the body, the harder it is to keep the limbs bent, let alone maintain a crouched posture. Large-bodied ungulates stand with the limbs minimally bent, as well as having necks long enough to avoid resorting to bipedal standing, which for normally quadrupedal animals becomes less and less efficient the larger the body size.

Hares have a short neck (http://museu.ms/collection/object/253558/lepus-europaeus-pallas-1778 and https://www.facebook.com/522456097810699/photos/same-species-different-ages-nope-on-the-left-you-see-a-lynx-skeleton-and-on-the-/1105375776185392/ and https://www.alamy.com/stock-photo-brown-hare-lepus-europaeus-stretching-warwickshire-136611136.html and https://www.alamy.com/brown-hare-stretching-in-a-frozen-meadow-in-winter-gb-image151883820.html and https://www.alamy.com/brown-hare-lepus-europaeus-stretching-after-resting-in-form-in-grass-image2983291.html and https://www.alamy.com/stock-photo-european-hare-lepus-europaeus-adult-stretching-in-grass-field-suffolk-49033927.html.).

The neck of even the lankiest hare, Lepus alleni (body mass about 4 kg, https://www.inaturalist.org/observations/7840174 and https://www.alamy.com/stock-photo-antelope-jackrabbit-lepus-alleni-oracle-pinal-county-arizona-united-13554693.html), remains shorter than that of like-size bambis (https://www.freepik.com/premium-photo/small-antelope-dik-dik-walking-african-savannah_8659869.htm and https://en.wikipedia.org/wiki/G%C3%BCnther%27s_dik-dik#/media/File:Guenther's_Dik-dik_(Madoqua_guentheri_smithii)_(7662529270).jpg and https://www.alamy.com/guenthers-dik-dik-madoqua-guentheri-male-walking-in-dry-grass-samburu-national-reserve-kenya-image462234785.html and https://www.sciencephoto.com/media/873025/view).

In compensation for a short neck, hares are able to

• forage on small plants by means of crouching, and
• maintain vigilance by means of bipedal standing.

The bipedal postures used by hares for vigilance are:

• usually plantigrade, with the hind soles horizontal on the ground (https://www.shutterstock.com/nb/image-photo/large-jackrabbit-standing-upright-looking-sideways-272293895 and https://www.tmparksfoundation.org/animals/black-tailed-jackrabbit and http://cannundrum.blogspot.com/2020/09/jackrabbit-love.html),
• but sometimes digitigrade, with the hind soles vertical (https://www.gettyimages.com.au/detail/photo/jump-royalty-free-image/89348401?adppopup=true and https://www.alamy.com/arctic-hare-lepus-arcticus-standing-on-hind-legs-ellesmere-island-canada-august-image357436273.html and https://www.nature.ca/notebooks/english/archare_p2.htm and https://www.istockphoto.com/photo/arctic-hare-greenland-gm469405858-61577704).

Neither of the above bipedal postures are used for vigilance in bambis or any other any ungulates. This is because ruminants

• are anatomically incapable of any plantigrade bipedal postures,
• stand bipedally not for vigilance but instead for social interactions or foraging (see https://www.inaturalist.org/journal/milewski/56018-bipedal-versatility-in-ruminants-part-1#), and
• have a relatively long neck on which to lift the eyes and ears.

The postural specialisation of hares may thus preclude much increase in body size.

SPECIALISATION IN LOCOMOTION

Hares have soft soles, but can run as speedily - and with as much endurance - as any animal of their body size.

Hares are unique among cursorial (https://en.wikipedia.org/wiki/Cursorial) mammals in possessing soles that are fully furred (https://www.alamy.com/hare-stretching-itself-and-preparing-to-run-away-image363826064.html and https://www.gettyimages.com.au/detail/photo/european-brown-hare-royalty-free-image/169837141?adppopup=true and https://www.agefotostock.com/age/en/details-photo/european-hare-lepus-europaeus-running-away-back-side/BWI-BLW028037 and https://www.gettyimages.com.au/detail/news-photo/hunting-bird-chases-and-catches-its-prey-a-hare-during-a-news-photo/106369083?adppopup=true and http://www.arthurgrosset.com/mammals/photos/lepeur13951.jpg and https://naturallycuriouswithmaryholland.wordpress.com/2015/02/27/snowshoe-hare-hind-feet/).

When galloping at full speed, hares maintain traction by means of the four claws on each hind foot, which are not enlarged or otherwise specialised. All known mammals achieving a combination of speed and endurance, at body masses exceeding 50 kg, have modified claws - the most extreme of which are hooves.

The locomotory specialisation of hares may thus preclude much increase in body size.

This conceptual framework allows comparison of hares with ungulates in a fairly categorical way. In the case of rodents, comparisons are complicated because this order shares several of the features, described above, of lagomorphs.

For example, various rodents

• systematically eat their feces (e.g. Cavia, https://pubmed.ncbi.nlm.nih.gov/2866874/),
• have long ears (e.g. Euchoreutes, https://www.audubon.org/news/meet-jerboa-enormous-eared-jumping-rodent-foot-fetish and https://en.wikipedia.org/wiki/Long-eared_jerboa),
• have vertically-oriented pupils (e.g. Chinchilla, https://www.deviantart.com/fohat/art/Chinchilla-Eye-45026505),
• maintain vigilance bipedally (e.g. Urocitellus, https://www.activewild.com/arctic-ground-squirrel/), or
• bound-walk (e.g. Pedetes, https://www.youtube.com/watch?v=P0bGmYi8L44), or
• have furry soles (e.g. Dipus, https://inaturalist.ca/taxa/43878-Dipus-sagitta).

Why have the constraints, referred to above, not limited all herbivorous rodents in increasing their body size?

The key lies in explaining why, although certain large-bodied herbivorous rodents have evolved, none has rivalled the ecological versatility of ungulates or the intercontinental success of hares.

It is noteworthy that:

• the largest-bodied cursorial rodent, namely Dolichotis patagonum (https://en.wikipedia.org/wiki/Patagonian_mara and https://academic.oup.com/mspecies/article/doi/10.2307/0.652.1/2600781?login=false), occurs on a continent devoid of indigenous hares, and does not exceed the largest-bodied hare in body mass,
• no extinct form of cursorial rodent (including forms of Dolichotis in the Pleistocene) is known to have been larger-bodied than D. patagonum (https://www.sciencedirect.com/science/article/pii/S1631068318301350), and
• the largest-bodied extant rodents, namely beavers (https://books.google.com.au/books?id=2bvlBgAAQBAJ&pg=PA17&lpg=PA17&dq=Beaver+caecotrophy&source=bl&ots=HCFNbnRyKU&sig=ACfU3U0MA1MNVBbdSCYORsMELqHHzBzT1A&hl=en&sa=X&ved=2ahUKEwiElaW88rD3AhVNzTgGHQ9nATcQ6AF6BAgSEAM#v=onepage&q=Beaver%20caecotrophy&f=false) and the capybara (https://en.wikipedia.org/wiki/Capybara#Diet_and_predation), are not cursorial, instead depending on refuge in water.

Given that hares overlap with ungulates in body size, and are similar in various ways to rodents, why have they evolved in the first place? What is the overall niche of hares, and how have they proven competitively superior to bambis and the rodents most resembling hares?

Instead of evolving in directions that would lead to competition with large-bodied herbivores, hares have capitalised on ungulates by fitting into the interstices of the herbivorous guild (https://en.wikipedia.org/wiki/Guild_(ecology)). Hares generally depend on large-bodied mammals to keep vegetation open and to create patches temporarily overutilised to the degree that the quantity of food available is small.

Partly because hares have the most efficient digestion known in the category of hindgut-fermentation, they rival the reproductive rates of the most fecund rodents while exceeding all rodents in cursoriality. And such fecundity and fleeing is necessary for the survival of hares, because they are subject to the various predators supported by all the ungulates and rodents sharing the same guild.

In conclusion, hares may be better-adapted for certain niches than are either ungulates or rodents. However, their syndrome of specialisations in digestion, vigilance, posture, and locomotion is likely to lose its competitive edge beyond the range in body masses currently seen in hares, viz. 2-6 kg.

And another way of summarising these findings is that perhaps the overarching specialisation for lagomorphs is a specialisation in body size itself.

@tfrench @biohexx1 @maxallen @napoleon1799 @mooseandsquirrel @aguilita @marcelo_aranda @lefebvremax @kevinatbrakputs @colin25 @aguilita @zarek @beartracker @douglasriverside @jakob @michalsloviak @jkfrey @je9h @apgarm @chewitt1 @rion_c @ludwig_muller @simontonge

It is clear that Lepus possesses a complex repertoire of flags.

Are their messages directed to potential predators, or conspecifics, or both? Since most species are effectively solitary, it seems unlikely that the flags function mainly to warn conspecifics. Instead, a plausible function is to signal to the potential predator that

• it has been detected, discouraging further stalking, and
• the individual hare is fit, discouraging pursuit.

Lepus varies in colouration from

• plain-coloured and inconspicuous (e.g. Lepus americanus in full seasonal coats, https://www.inaturalist.org/observations/106555675 and https://www.inaturalist.org/observations/101379283), through
• inconspicuous when the figure is at rest but with up to four clearly-illustrated flags when active (on various combinations of feet, tail, and both the anterior and the posterior surfaces of the ear pinnae) in e.g. Lepus townsendii (https://www.inaturalist.org/observations/43268453 and https://www.inaturalist.org/observations/67069574), through
• conspicuous by virtue of haunch-flags activated by twitching of the skin (Lepus alleni, Lepus callotis), to
• conspicuous on snow-free backgrounds, owing to overall paleness of the figure (e.g. northernmost Lepus arcticus in the winter coat, http://kratlusk.blogspot.com/2010/07/huge-hare-herd-lhh.html).

The above variation corresponds to

• flags poorly-developed, through
• flags well-developed (https://www.alamy.com/stock-photo-a-white-tailed-jackrabbit-running-in-a-field-91812312.html), through
• flags shifted from the extremities to the body itself, where activated by twitching of the skin, to
• flags subsumed by the overall conspicuousness of the figure (plus gregariousness in the case of L. arcticus (https://www.mindenpictures.com/stock-photo-arctic-hare-lepus-arcticus-group-on-tundra-ellesmere-island-nunavut-naturephotography-image00064679.html) and some subspecies of L. timidus).

In the boreal biome, the inconspicuous colouration of L. americanus is consistent with the reliance of this species on

• the cover of woody plants in the case of the summer coat, and
• a background of deep snow in the case of the winter coat.

In the tropics, the poor development of flags in L. nigricollis (https://lakesideindia.files.wordpress.com/2013/03/march-hare.jpg) may likewise be partly explained by the dependence of this Indian species on woody cover - although the vegetation is quite different.

The tail varies considerably among the species of hares in size and shape. It is noteworthy that the conspicuousness of the tail has been reduced in L. californicus (https://sabinonaturalists.org/critters/black-tailed-jack-rabbit/), by the reduction of the dark-pale contrast between the upper surface and the lower surface.

In hares, unlike ruminants, the tail is normally held 'erect' in sitting/crouching postures, being 'lowered' only when the figure stands or locomotes (https://www.alamy.com/black-tailed-jackrabbit-on-the-move-lepus-californicus-hare-native-merced-national-wildlife-refuge-san-joaquin-valley-merced-county-california-image425323824.html and https://www.shutterstock.com/nb/image-photo/wild-grey-rabbit-jumping-around-on-1727626519). The 'erect' tail is inconspicuous because it is close to ground-level and effectively horizontal, and hidden by the curve of the hindquarters (https://www.flickr.com/photos/38971900@N08/15362183597).

The form and colouration of the tail in Lepus falls into at least six categories (qualification for caudal flag denoted by asterisk*), as follows:

Tail proportionately small and correspondingly inconspicuous: alleni (https://www.inaturalist.org/observations/1103230)

Tail of medium size:

• Tail white on white hindquarters: winter coat in arcticus, americanus, timidus, townsendii (e.g. https://fieldguide.mt.gov/speciesDetail.aspx?elcode=AMAEB03040)
• *Tail white on medium-tone hindquarters: oiostolus and summer coat in arcticus, timidus (https://www.agefotostock.com/age/en/details-photo/mountain-hare-lepus-timidus-adult-summer-coat-running-on-moorland-peak-district-derbyshire-england-april/FHR-10514-00281-795)
• *Tail dark on pale hindquarters: callotis (https://inaturalist.ala.org.au/observations/104689188)
• Tail medium-tone on medium-tone hindquarters: californicus, nigricollis (https://www.inaturalist.org/observations/97706483)
• *Tail dark on upper side and pale on lower side, on medium-tone hindquarters: saxatilis, capensis, victoriae, starcki, europaeus, granatensis (e.g. https://www.inaturalist.org/observations/99911341)

*Tail proportionately large and correspondingly conspicuous: townsendii in summer coat (e.g. https://alchetron.com/White-tailed-jackrabbit and https://www.youtube.com/watch?v=IMdfCptUxDc).

Given that the ear pinnae are longer than the tail in all species of hares, it is unsurprising that auricular flags are present in at least ten species.

What is surprising, instead, is that the ear pinnae have inconspicuous colouration in several species. For example, Lepus europaeus and L. capensis are so closely related that they may constitute a superspecies. Yet the latter (https://www.inaturalist.org/observations/70618803) differs from the former (https://www.inaturalist.org/observations/39641267) in lacking dark-pale contrast on the posterior surface of the ear pinnae - the observations of https://www.semanticscholar.org/paper/Ear-flashing-behaviour-of-cape-hares-(Lepus-in-Kamler/b4de4af4953cf3a80c60e22c8867b08feffe6876 notwithstanding.

The relationship between caudal and auricular (on the posterior surface of the ear pinnae) flags falls into the following categories:

• both so poorly-developed that I have found no illustrations (e.g. americanus)
• both present (e.g. europaeus https://www.inaturalist.org/observations/52383467, winter coat in timidus)
• caudal flag present but auricular flag absent (e.g. saxatilis https://www.projectnoah.org/spottings/17736127/fullscreen)
• auricular flag present but caudal flag absent (e.g. californicus https://www.inaturalist.org/observations/79491708, winter coat in townsendii https://www.inaturalist.org/observations/66858691).

There is a tendency in Lepus for the tips of the ear pinnae to be dark. However, it is only in L. townsendii in winter coat that this dark feature constitutes the entire pattern of the auricular flag (on the posterior surface of the ear pinnae). In e.g. L. europaeus, L. granatensis, and L. starcki, and some subspecies/individuals of L. timidus, the auricular flag on the posterior surface of the ear pinnae is punctuated by dark tips, but is conspicuous mainly owing to its paleness relative to the ground-colour of the figure.

The auricular flag on the posterior surface of the ear pinnae of Lepus callotis (https://www.inaturalist.org/observations/84012403) is differently configured from that in L. californicus (https://www.inaturalist.org/observations/39597865), despite these species being partly sympatric.

Lepus alleni is the only species in which the only flag is a haunch-flag, activated by twitching of the skin (scroll in http://feathertailedstories.blogspot.com/2017/). This produces a flashing effect analogous with that in Antilocapra americana (https://en.wikipedia.org/wiki/Pronghorn).

I have been unable to document any flags in several species of Lepus because too few photos are available. This includes e.g. L. coreanus (https://www.inaturalist.org/taxa/43144-Lepus-coreanus) and L. sinensis (https://www.inaturalist.org/taxa/43142-Lepus-sinensis), which occur in Korea and China respectively.

Flags are, by their nature, activated by movement. In Lepus, the movements are complex. In the following, I have tried to list them in increasing order of complexity in the context of reactions to potential predators:

• erecting the ear pinnae shows the auricular flags in all species (https://www.shutterstock.com/nb/image-photo/blacktail-jackrabbit-lepus-californicus-sitting-remote-73173493),
• holding the tail horizontal while fleeing, so that it wags somewhat up-and-down with the gait (https://stock.adobe.com/sk/search/images?k=jackrabbit+running&asset_id=60780157), producing a caudal flag in those species possessing tails with dark on the upper side and contrasting pale on the lower side (pronounced wagging of the tail is unusual in Lepus, with side-to-side wagging not having been recorded),
• going from a crouching to a sitting posture, with ear pinnae erect and flanks visible, can show not only auricular flags but also (in the case of L. callotis and L. alleni) haunch-flags, and possibly (in e.g. L. arcticus in the summer coat) pedal flags,
• fleeing shows auricular (only on the posterior surface of the ear pinnae), caudal, and haunch-flags, but not pedal flags,
• alternating movement of the ear pinnae (left vs right) while fleeing 'flashes' the auricular flag (this has been recorded mainly in L. californicus but probably occurs also in other species),
• alternating twitching of the skin on haunches and flanks (left vs right), as the fleeing individual zig-zags with haunch-flag activated, and
• stotting (recorded unambivalently only in L. arcticus, L. alleni, and L. callotis, all of which use bipedal hopping gaits at times) emphasises the display of all the flags shown by fleeing.

However, please note that caudal flags can be relevant also to intraspecific (particularly sexual) behaviour. During courtship, males of L. europaeus micturate on females while flashing the white lower surface of the tail (https://publish.iupress.indiana.edu/read/how-animals-communicate/section/a65f3527-f41e-4db2-a292-d7334cd4b38e). Similar behaviour probably occurs in other species.

The fact that only three species use bipedal stotting gaits is partly explained by the large body size of L. arcticus and L. alleni, the gregariousness of L. arcticus and L. alleni, and the pair-bonded social structure of L. callotis.

LEPUS EUROPAEUS

Lepus europaeus (https://academic.oup.com/mspecies/article/52/997/125/6046128?login=false#220119974) has both a caudal flag and an auricular flag. The latter is on the posterior surface of the ear pinnae. Both flags are conspicuous by virtue of dark-pale contrasts.

The following shows that the anterior surface of the ear pinnae in L. europaeus has disruptive colouration (https://www.inaturalist.org/observations/27569507 and https://www.inaturalist.org/observations/65142239 and https://www.inaturalist.org/observations/5486673 and https://www.inaturalist.org/observations/53918093 and https://en.wikipedia.org/wiki/Disruptive_coloration): https://www.inaturalist.org/observations/101976575 and https://www.inaturalist.org/observations/71858152 and https://www.inaturalist.org/observations/68333414. This surface is marked, not plain, but with an inconspicuous effect unlikely to function as a flag

The following show the caudal and auricular flags on the fleeing figure, as viewed from behind:

https://www.inaturalist.org/observations/39641267
https://www.inaturalist.org/observations/52383467
https://www.inaturalist.org/observations/102179162
https://www.inaturalist.org/observations/107695988
https://www.inaturalist.org/observations/106683594
https://www.inaturalist.org/observations/105936073
https://www.inaturalist.org/observations/104256833
https://www.inaturalist.org/observations/101452331
https://www.inaturalist.org/observations/79643922
https://www.inaturalist.org/observations/72254135
https://www.inaturalist.org/observations/72013700
https://www.inaturalist.org/observations/66647421

The following show possible stotting: https://www.inaturalist.org/observations/106614136 and https://upload.wikimedia.org/wikipedia/commons/1/13/Feldhase%2C_Lepus_europaeus_2a.JPG and https://www.agefotostock.com/age/en/details-photo/european-hare-lepus-europaeus-adult-male-running-stotting-back-to-female-in-grass-field-suffolk-england-march/FHR-10512-00774-842 and https://www.inaturalist.org/observations/73530651 and https://www.inaturalist.org/observations/73202777.

Lepus starcki (https://www.inaturalist.org/observations/42420359) of the Ethiopian Highlands and Lepus tolai (https://www.inaturalist.org/observations/67741385) of central Asia seem similar to L. europaeus with respect to flags.

LEPUS OIOSTOLUS

Lepus oiostolus seems similar to L. europaeus in its auricular flag: https://www.mammalsofindia.org/#!/sp/407/Lepus-oiostolus.

The caudal flag of this species differs from that of L. europaeus in being paler. This is because:

• the tail has a grey upper surface (https://www.wildwondersofchina.com/image/I0000RpHyivtisLU), but
• its fluffiness means that the caudal flag is effectively white (https://www.flickr.com/photos/reurinkjan/6217057489 and https://www.alamy.com/stock-photo-woolly-hare-lepus-oiostolus-can-be-found-in-high-altitude-meadow-steppes-88604964.html and https://ainawgsd.tumblr.com/post/184577500057/woolly-hare).

LEPUS GRANATENSIS

Lepus granatensis replaces L. europaeus on the Iberian Peninsula. It shares the flags described above (https://www.inaturalist.org/observations/104415801 and https://www.inaturalist.org/observations/69733160 and https://www.inaturalist.org/observations/62918470). However, it possesses an additional auricular flag on the anterior surface of the ear pinnae: https://www.inaturalist.org/observations/21432998 and https://www.inaturalist.org/observations/62977862.

LEPUS NIGRICOLLIS

No flag is consistently present in the Indian species Lepus nigricollis.

This is because:

• the nape is not consistently dark (e.g. https://www.team-bhp.com/forum/attachments/travelogues/948589d1340910540-gurgaon-ranthambhore-jodhpur-gurgaon-big-cats-call-again-7015.jpg),
• the black nape, where present, does not consistently have adjacent fur pale enough to produce dark-pale contrast (http://cannundrum.blogspot.com/2019/05/indian-hare.html and https://www.indiawilds.com/forums/showthread.php?14257-Black-Naped-Hare-Bandipur),
• the ear pinnae are plain-coloured on both the anterior and the posterior surfaces,
• the upper surface of the tail is not consistently dark (https://www.team-bhp.com/forum/attachments/travelogues/948589d1340910540-gurgaon-ranthambhore-jodhpur-gurgaon-big-cats-call-again-7015.jpg and https://lakesideindia.wordpress.com/tag/indian-hare/ and https://ainawgsd.tumblr.com/post/183826793037/the-indian-hare-lepus-nigricollis-also-known-as and https://lakesideindia.files.wordpress.com/2013/03/black-naped-hare.jpg and https://lakesideindia.files.wordpress.com/2013/03/march-hare.jpg and https://lakesideindia.files.wordpress.com/2013/03/indian-blacknaped-hare.jpg and https://lakesideindia.files.wordpress.com/2013/03/blacked-naped-hare-tamil-nadu-india.jpg and https://lakesideindia.files.wordpress.com/2013/03/1.jpg).

LEPUS SAXATILIS

Lepus saxatilis of southern Africa has a proportionately long tail (https://southafrica.co.za/scrub-hare.html and https://www.inaturalist.org/observations/10980141 and https://www.inaturalist.org/observations/109839643 and https://www.inaturalist.org/observations/100057300 and https://www.shutterstock.com/nb/image-photo/big-eared-hare-on-roadside-drakensberg-1140501887).

Furthermore, the tail presents dark-pale contrast (https://www.inaturalist.org/observations/11119448 and https://www.inaturalist.org/observations/64754481 and https://www.inaturalist.org/observations/108534715).

However, its ear pinnae are plain-coloured (https://www.inaturalist.org/observations/99066204 and https://www.inaturalist.org/observations/96201128 and https://www.inaturalist.org/observations/71211493 and https://www.inaturalist.org/observations/103600911 and https://biodiversityfocused.co.za/hares-rock-rabbits-rabbits-lagomorpha/#prettyPhoto[gallery99]/0/).

The following show the caudal flag on the figure, as viewed from behind:

https://www.inaturalist.org/observations/66306315
https://www.projectnoah.org/spottings/17736127/fullscreen
https://www.inaturalist.org/observations/103324289
https://www.inaturalist.org/observations/100057269
https://www.inaturalist.org/observations/99911341

LEPUS VICTORIAE

Lepus victoriae, widespread in the tropical savannas of Africa, resembles L. saxatilis in the colouration of its ear pinnae (https://www.inaturalist.org/observations/42293850) and its tail (https://www.inaturalist.org/observations/36366737).

However, its tail seems proportionately smaller in West Africa (subspecies canopus, https://www.inaturalist.org/observations/68062109) than in East Africa (https://www.agefotostock.com/age/en/details-photo/scrub-hare-lepus-saxatilis-samburu-reserve-kenya-africa/MEV-10866491).

The following show the caudal flag on the fleeing figure, as viewed from behind:

https://www.canstockphoto.com/alert-scrub-hare-lepus-saxatilis-39241745.html
https://www.canstockphoto.com/alert-scrub-hare-lepus-saxatilis-39241746.html
https://www.inaturalist.org/observations/45774821
https://www.inaturalist.org/observations/39650232

LEPUS CAPENSIS

Lepus capensis is widespread in treeless vegetation in Africa and the Middle East. It resembles L. saxatilis with respect to its caudal flag and lack of auricular flags:

https://www.inaturalist.org/observations/11080636
https://www.inaturalist.org/observations/34131075
https://www.inaturalist.org/observations/70618803
https://www.inaturalist.org/observations/106320494
https://www.inaturalist.org/observations/102073907
https://www.inaturalist.org/observations/65029120
https://www.inaturalist.org/observations/50801505
https://www.inaturalist.org/observations/35021772

to be continued...

@brucebennett @oviscanadensis_connerties @don-jean @rangertreaty50 @tfrench @apgarm @jkfrey @ken_j_allison @napoleon1799 @beartracker @johnnybirder

LEPUS ARCTICUS

Lepus arcticus (https://academic.oup.com/mspecies/article/doi/10.2307/3504088/2600694?login=false) is mainly white with black-tipped ear pinnae, although southerly populations feature a summer coat.

This species differs from most other hares in the following ways. It:

• is the largest-bodied species (particularly at the highest latitudes, where body mass can reach 6.8 kg) but with proportionately short ears
• tends to remain white year-round,
• is gregarious (https://www.alamy.com/stock-photo-arctic-hare-lepus-arcticus-group-on-tundra-ellesmere-island-nunavut-125240761.html) and in some situations somewhat migratory,
• tends to live on snow-free, bare, rocky/stony terrain, i.e. against a dark background (e.g. https://www.alamy.com/wild-arctic-hare-sitting-in-greenland-tundra-image352809466.html) where the paleness of its coat prevents hiding, and
• has unique stotting gaits, consisting of bipedal hopping (https://www.youtube.com/watch?v=KPm3SR5lz0o and https://www.wildlifearchives.com/pin/6599/) as well as three-legged running (possibly illustrated by https://www.alamy.com/arctic-hare-lepus-arcticus-hopping-around-the-snow-in-canadas-arctic-tundra-arviat-nunavut-image464727485.html).

All of the above make for a degree of exposure (by daylight) and self-advertisement unusual in hares. The whole figure tends to be so conspicuous that flags are somewhat redundant.

Best and Henry (1994) describe stotting without acknowledging it as such:

"The usual gait is a series of four-legged hops, each hop carrying the hare ca. 1.2 m. Southern populations use this gait almost entirely, but northern races, found on Arctic islands from northern Baffin Island northward, use a different gait (Banfield,1974). Hopping on the hind feet without touching the forefeet to the ground has been reported for L. arcticus (Hall, 1951). When disturbed, the Arctic hare stands erect on its hind legs, forefeet tucked close to its body (Feilden, 1877), and hops about until the source of danger is located (Pruitt, 1960); if not frightened, the hare resumes feeding. If startled, it runs in a series of bounds, generally with one foreleg lifted up. This gives tracks in snow the appearance of having been made by a three-legged animal (Feilden,1877). When a group is frightened, the whole group may stand upon their hind legs and without using their forelegs, hop away in every direction in long jumps; only when they have located the danger do they use all four legs to bound away. When they have gone a suitable distance, some may stand up on their hind legs, and with ears raised look to all sides to get their bearings, and then disappear (Freuchen, 1935). Arctic hares may double back on their own trail for4.5-9.0 m, then leap off to one side. One Arctic hare doubled back for a distance of 300 m (Sutton and Hamilton, 1932)....On Ellesmere Island, a wolf approached a group of 125 Arctic hares in sunlight at 0300 h on 10 August. The hares were grazing over an area of ca. 0.4 ha on a hillside. The wolf singled out an individual at the edge of the group and chased it through the group. The hare being chased hopped rapidly on its hind legs much like a kangaroo, but the remaining hares, after the initial alarm, paid little attention to the wolf running through the group. The hare being pursued ran in a zig-zag manner through the group, then left it to ascend a hill where the wolf captured it (Tener, 1954)."

Note that the above authors assume that the main function of bipedal hopping is to gain height in spotting an approaching predator. More likely it is a display of individual fitness to a predator already spotted.

The mainly greyish summer coat of L. arcticus features at least four flags, viz.:

• a caudal flag and a pedal flag (by virtue of the fact that the tail and feet remain white throughout the year), as well as
• two different auricular flags (by virtue of conspicuous dark and pale markings on both the anterior and posterior surfaces of the ear pinnae).

Please see: https://www.inaturalist.org/observations/110623961 and https://www.inaturalist.org/observations/70225456 and https://www.inaturalist.org/observations/66470343.

In the white winter coat, the whole figure is conspicuous when the animal is active on snow-free ground. No particular feature qualifies as a flag, because:

• the white tail conforms to the rest of the figure, and
• the dark tips of the ear pinnae are too small to be conspicuous.

What is the function of the dark tips of the ear pinnae?

One possibility is:

to distract the attention of scanning predators away from the real eyes (which are similar in darkness and size, see https://www.alamy.com/stock-photo-arctic-hare-lepus-arcticus-hudson-bay-canada-141449523.html and https://www.alamy.com/adult-arctic-hare-lepus-arcticus-outside-churchill-northern-manitoba-image2868054.html and https://www.reddit.com/r/aww/comments/ocfgc/cute_arctic_harefirst/ and https://www.alamy.com/arctic-hare-lepus-arcticus-in-the-snow-churchill-manitoba-canada-image384835136.html and https://www.alamy.com/stock-photo-arctic-hare-in-snow-17302820.html) when the figure of L. arcticus is inconspicuous by virtue of being stationary on a snowy background.

If so, this would in a sense be the opposite of a flag.

Lepus othus (https://en.wikipedia.org/wiki/Alaskan_hare) seems similar to L. arcticus, with respect to the occurrence of flags.

LEPUS AMERICANUS

Lepus americanus is unlike L. arcticus in having inconspicuous colouration and behaviour.

This species is plain-coloured in most subspecies, in summer coat and winter coat. Caudal and auricular flags are poorly-developed.

There are pedal and auricular flags in transitional coat (see https://www.jstor.org/stable/1374046) in some subspecies/individuals:

• spring coat (https://www.shutterstock.com/nb/image-photo/snowshoe-hare-varying-brown-coat-closeup-1571329048 and https://www.shutterstock.com/nb/image-photo/snowshoe-hare-varying-brown-coat-spring-527299774), and
• autumn coat (https://www.shutterstock.com/nb/image-photo/white-snowshoe-hare-winter-251938918 and https://www.gettyimages.com.au/detail/photo/creative-brief-nature-and-wildlife-snowshoe-hare-royalty-free-image/1047357850?adppopup=true).

Summer coat:
https://www.shutterstock.com/nb/image-photo/eastern-cottontail-standing-on-edge-path-680897974
https://www.inaturalist.org/observations/90729949
https://www.inaturalist.org/observations/101379283
https://www.inaturalist.org/observations/95089838
https://www.inaturalist.org/observations/105434881
https://www.inaturalist.org/observations/89503059
https://www.inaturalist.org/observations/102531373

Winter coat:
https://www.inaturalist.org/observations/106555675
https://www.gettyimages.com.au/detail/photo/snowshoe-hare-portrait-royalty-free-image/584421721?adppopup=true

Lepus brachyurus (https://www.inaturalist.org/taxa/43139-Lepus-brachyurus) of Japan seems similar to L. americanus (see https://animalia.bio/japanese-hare). Some individuals in the summer coat show a small caudal flag (short tail with dark on the upper surface and pale on the lower surface) but no auricular flag. Some individuals in what may be a seasonally transitional coat show an auricular flag on the posterior surface of the ear pinnae, consisting of pale with a dark patch at the tip (https://en.wikipedia.org/wiki/Japanese_hare#/media/File:Lepus_brachyurus,_March,_Tsukuba,_Japan.jpg).

LEPUS TIMIDUS

Lepus timidus (https://academic.oup.com/mspecies/article/doi/10.2307/3504302/2600716?login=false) is not as plain-coloured as L. americanus, being in some respects intermediate among L. arcticus, L. americanus, and L. townsendi. This species is difficult to describe because it has so many subspecies.

In the winter coat, L. timidus possesses no flags (https://www.inaturalist.org/observations/40365203 and https://www.inaturalist.org/observations/48219583).

However, in subspecies L. t. scoticus and L. t. canescens, the winter coat is not white, and the anterior surface of the ear pinnae remain dark enough possibly to qualify as an auricular flag.

In the summer coat:

• the white tail potentially qualifies as a caudal flag (https://www.gettyimages.com.au/detail/photo/mountain-hare-adult-in-summer-coat-running-on-a-royalty-free-image/1218872932?adppopup=true and https://stock.adobe.com/ee/search?k=running+hare&asset_id=216027209), and
• auricular flags are present on both the anterior and the posterior surfaces of the ear pinnae (e.g. https://www.alamy.com/stock-photo-arctic-hare-lepus-timidus-varronis-moulting-portrait-canton-of-schwyz-89069354.html and https://commons.wikimedia.org/wiki/File:Lepus_timidus_ainu.jpg and https://www.inaturalist.org/observations/82578916 and https://www.inaturalist.org/observations/49504754).

Autumn coat
https://www.inaturalist.org/observations/63896793
https://www.inaturalist.org/observations/36055131
https://www.alamy.com/stock-photo-mountain-hare-lepus-timidus-scotland-uk-121902717.html

Spring coat
https://www.inaturalist.org/observations/48175173
https://www.inaturalist.org/observations/42304908

The following show possible stotting in L. timidus: https://www.alamy.com/mountain-arctic-hare-lepus-timidus-cairngorm-scottish-highlands-image6960489.html and https://www.alamy.com/stock-photo-the-mountain-hare-lepus-timidus-also-known-as-blue-hare-here-seen-101106559.html.

In partial summary, interpretation of the colouration of L. arcticus is complicated by the fact that the white colouration occurs not only in snow but also in dark, snow-free terrain. This means that the whole figure of this large-bodied species can be conspicuous by virtue of its paleness. Furthermore, this overall conspicuousness may be consistent with the stotting displays of L. arcticus, which consist of non-quadrupedal gaits unknown in most other species of hares.

to be continued...