פברואר 21, 2024

The mystery of tongue-protruding behaviour in ruminants, beginning with impalas (Aepyceros)

@tonyrebelo @jeremygilmore @beartracker @paradoxornithidae @capracornelius @dejong @botswanabugs @nyoni-pete

Recently, I noticed that impalas (Aepyceros) have often been photographed with the tongue protruding.

I do not refer to the cleaning if the nostrils by means of the tongue (https://www.shutterstock.com/image-photo/portrait-female-impala-gazelle-that-just-194312933 and https://www.alamy.com/impala-aepyceros-melampus-licking-the-nose-south-africa-krueger-national-park-image255236547.html?imageid=E2254136-C33E-4AEF-967E-8AE5F7223EF6&p=853426&pn=14&searchId=c815bc09b660ce5ed5c0dd5d690ef024&searchtype=0), which occurs in many ruminants (https://www.alamy.com/stock-photo-white-tailed-deer-doe-with-tongue-sticking-out-cades-cove-great-smoky-52364585.html?imageid=E118A7F9-23AF-492C-900B-A099517111E9&p=4052&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0 and https://www.dreamstime.com/eland-antelope-oryx-taurotragus-scientific-name-can-grow-up-to-m-weighs-kg-living-years-nature-lives-parts-south-image155017395 and https://www.dreamstime.com/nyala-tragelaphus-angasii-portrait-male-tongue-image185606287 and https://www.istockphoto.com/photo/roe-deer-licking-in-forest-in-autumn-nature-in-close-up-gm1423413930-468412317?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm and https://www.flickr.com/photos/tobiasnawrath/14005864955).

Nor do I refer to the tongue-flicking expression - puzzling as this is in certain ways - seen in hectic activities during masculine display in impalas (https://www.shutterstock.com/image-photo/male-impala-extends-tongue-court-female-1081363733 and https://www.alamy.com/stock-photo-impala-aepyceros-melampus-sticking-out-tongue-kruger-national-park-32926983.html?imageid=B03A49BE-5521-4310-81F5-EBBDD570D34A&p=46605&pn=16&searchId=e3ed3ee9ce6844b46525748256064dd8&searchtype=0 and https://www.dreamstime.com/adult-impala-walking-dry-grass-tongue-out-moremi-okavango-delta-botswana-vertical-portrait-male-impala-sticking-image198684891).

Instead, I refer to the following:
Juveniles:
https://www.shutterstock.com/image-photo/kruger-national-park-baby-impala-summer-1926566396
https://www.dreamstime.com/male-impala-wild-sticking-tongue-out-image143766031
Adult females:
https://www.shutterstock.com/image-photo/female-impala-aepyceros-melampus-sticking-out-421869316 and https://www.shutterstock.com/image-photo/female-impala-aepyceros-melampus-sticking-out-420080788
https://www.shutterstock.com/image-photo/impala-showing-her-tongue-botswana-africa-1229219770
https://www.pinterest.com.au/pin/294985844318116914/
https://www.shutterstock.com/image-photo/close-female-common-impala-extending-tongue-1878509461
https://www.shutterstock.com/image-photo/closeup-shot-tongue-out-antelope-2051598548
https://www.shutterstock.com/image-photo/shot-impala-tongue-out-kruger-national-633095888
https://www.shutterstock.com/image-photo/close-female-common-impala-showing-tongue-2259956643
https://www.alamy.com/close-up-of-female-common-impala-extending-tongue-image402510156.html?imageid=32EE96C0-38B5-4C66-9536-EE0AEACE7458&p=2270282&pn=4&searchId=3d0b791c3d3cb7d50c9fda9d9d2afbe8&searchtype=0
Adult males:
https://www.istockphoto.com/photo/impala-sticks-tongue-out-gm91169035-6437029
https://www.shutterstock.com/image-photo/impala-sticking-tongue-out-709872856
https://www.shutterstock.com/image-photo/portrait-impala-natural-habitat-68518105
https://www.shutterstock.com/image-photo/tanzania-national-wildlife-refuge-impals-graze-1598818396
https://www.shutterstock.com/image-photo/impala-missing-horn-stands-showing-tongue-2275300017
https://www.shutterstock.com/image-photo/close-impala-ram-sticking-his-tongue-1429643615
https://www.shutterstock.com/image-photo/impala-sticking-tongue-out-1703975104
https://www.shutterstock.com/image-photo/impala-buck-sticks-out-his-tongue-485045428
https://www.shutterstock.com/image-photo/wild-african-impala-antelope-1-695835952
https://www.shutterstock.com/image-photo/impala-buck-browsing-on-twigs-bush-589866068
https://www.dreamstime.com/royalty-free-stock-images-cheeky-impala-image9557499
Scroll to second photo in https://worldanimalfoundation.org/advocate/wild-animals/params/post/1291286/impalas
https://www.dreamstime.com/closeup-springbok-antidorcas-marsupialis-sticking-out-tongue-etosha-national-park-namibia-closeup-springbok-antidorcas-image218800377

Tongue-protrusion in impalas seems odd, because

The puzzle lies in the following questions, in order of increasing importance:

My curiosity piqued by the above, I began to search among other ruminants.

I found that other bovids have, at least occasionally, been likewise photographed with the tongue protruding.

Tragelaphus euryceros:
https://www.dreamstime.com/antelope-tongue-extended-juvenile-bongo-image159300458

Nyala angasii:
https://es.123rf.com/photo_9112253_a-nyala-doe-sticks-out-her-black-tongue-in-anticipation-of-a-leafy-snack.html
https://www.dreamstime.com/doe-nature-antelope-zoo-sticks-out-her-tongue-funny-image171830405
https://www.dreamstime.com/lowland-nyala-tragelaphus-angasii-detail-portrait-nyala-nizzina-beautiful-female-funny-grimace-her-tongue-out-image246364436

Strepsiceros strepsiceros:
https://www.shutterstock.com/image-photo/common-eland-sticking-tongue-out-taurotragus-2061069446
https://www.alamy.com/close-up-of-male-greater-kudu-showing-tongue-image392279330.html
https://www.shutterstock.com/image-photo/closeup-female-kudu-antelope-sticks-out-2212651185
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-savannah-antelope-also-known-as-southern-plains-found-image226083170
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-also-known-as-southern-antelope-savannah-plains-found-image227924129
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-also-known-as-southern-antelope-savannah-plains-found-image229138672
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-savannah-antelope-also-known-as-southern-plains-found-image226083165
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-savannah-antelope-common-eland-sticking-its-tongue-out-image230245846
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-savannah-antelope-also-known-as-southern-plains-found-image231506697
https://www.dreamstime.com/common-eland-sticking-its-tongue-out-taurotragus-oryx-also-known-as-southern-antelope-savannah-plains-found-image229814727
https://www.dreamstime.com/greater-kudu-tragelaphus-strepsiceros-young-female-portrait-female-large-antelope-her-tongue-out-greater-kudu-image207855243
https://www.dreamstime.com/close-up-male-greater-kudu-extending-tongue-image205259222

Taurotragus oryx:
https://www.alamy.com/stock-photo-common-eland-taurotragus-oryx-male-sticking-out-tongue-portrait-african-48668592.html

Bison bison:
https://www.flickr.com/photos/scattered/44320317460

Kobus leche:
https://www.shutterstock.com/image-photo/portrait-antelope-tongue-out-zoo-1587458623 and https://www.dreamstime.com/portrait-antelope-tongue-out-zoo-image166569979

Kobus ellipsiprymnus:
https://www.dreamstime.com/antelope-its-tongue-hanging-out-looks-camera-portrait-young-female-african-waterbock-eating-food-image208243786
https://www.dreamstime.com/close-up-side-view-female-defassa-waterbuck-its-tongue-hanging-around-antelope-seen-safari-south-africa-image229087418
https://www.dreamstime.com/waterbucks-kobus-ellipsiprymnus-water-hole-sticking-his-tongue-out-ongava-private-game-reserve-neighbour-etosha-na-namibia-image261240558

Antidorcas marsupialis:
https://www.dreamstime.com/stock-photo-male-springbok-image3039700

Cephalophus niger:
https://www.dreamstime.com/stock-photo-duiker-west-african-black-antelope-close-up-image91511475
https://www.dreamstime.com/stock-photo-duiker-west-african-black-antelope-close-up-image91511604

These observations, as in impalas, deserve explanation.

However, the puzzle seems less than in impalas, because

Finally for now, I began to seek similar evidence among cervids.

What I found is that tongue-protrusion has indeed been recorded in cervids. However, I have yet to find any species in which the tongue is dark-pigmented.

Dama dama:
https://www.alamy.com/stock-photo-fallow-deer-dama-dama-sticking-tongue-out-91559034.html?imageid=519B7957-9524-4B31-AE67-7D04C055D59C&p=265029&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.alamy.com/mature-fallow-deer-stag-sticking-out-his-tongue-herd-of-dyrham-park-gloucestershire-uk-image224714683.html?imageid=F2F886BA-8EF6-46B5-9888-2A377070E5C7&p=75359&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.alamy.com/a-lovely-deer-who-stick-out-his-tongue-image330515522.html?imageid=5A6617DA-FE21-44E4-A392-91E7D0F8D10C&p=1149035&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.dreamstime.com/female-daniela-dama-sticking-out-her-tongue-close-side-view-autumn-poland-image297129173
https://www.istockphoto.com/photo/deer-with-her-tongue-out-gm1329261464-413058960?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm
https://www.shutterstock.com/image-photo/silly-deer-tongue-sticking-out-58217053
https://www.instagram.com/p/CxBrmtOhgjt/?ref=nextrace&hl=am-et
https://stock.adobe.com/au/images/a-young-spotted-deer-cervus-nippon-sticks-out-its-tongue-and-carefully-looks-into-the-distance-in-a-natural-habitat-against-a-background-of-grass/288866086

Cervus canadensis:
https://www.istockphoto.com/photo/elk-with-tongue-out-gm1360103164-433235215?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm
https://www.istockphoto.com/photo/roosevelt-elk-close-up-with-tongue-sticking-out-gm1490746294-515249683?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm

Cervus elaphus:
https://www.alamy.com/a-red-deer-doe-standing-in-a-hers-she-is-looking-left-and-had-her-tongue-out-a-red-deer-with-attitude-image401170427.html?imageid=C14F138C-31BA-43E0-9A77-8383A3A100CC&p=224192&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.alamy.com/stock-photo-red-deer-cervus-elaphus-standing-on-dried-grass-and-poking-his-tongue-76024788.html?imageid=325B0AD5-869B-4D6F-851D-2594C484B486&p=1142606&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.alamy.com/stock-photo-red-deer-cervus-elaphus-stag-checking-out-hinds-females-in-heat-by-172034422.html?imageid=89841021-D99C-422A-9F98-508DCC237C00&p=80876&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.istockphoto.com/photo/scottish-red-deer-stag-sticking-out-tongue-gm1965861936-558124889?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm
https://www.istockphoto.com/photo/red-deer-stag-in-bracken-with-tongue-out-gm1281052626-379192582?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm
https://www.shutterstock.com/image-photo/picture-deer-sticking-out-tongue-2369312293

Cervus nippon:
https://www.dreamstime.com/royalty-free-stock-images-antelope-showing-tongue-image22663779
https://stock.adobe.com/images/sika-deer-sticking-her-tongue-out/123976479
https://www.istockphoto.com/photo/spotted-deer-cute-face-expression-gm1273210106-375158699?phrase=deer+sticking+out+its+tongue&searchscope=image%2Cfilm

Odocoileus virginianus:
https://www.alamy.com/stock-photo-a-deer-sticking-out-its-tongue-41911968.html?imageid=747B8A64-BB93-43FB-A909-49C9DFE0A9D6&p=16407&pn=1&searchId=92c7e2275b61caf4ea73e5d8dd166422&searchtype=0
https://www.dreamstime.com/white-tail-deer-fawn-bitterroot-mountains-montana-field-sticking-his-tongue-out-image286079351
https://www.pinterest.com.au/pin/deer-reference--861102391238807765/

Odocoileus hemionus:
https://www.dreamstime.com/deer-wild-looking-camera-sticking-his-tongue-out-funny-animals-young-buck-meadow-eyebrows-image249389338

Axis axis:
https://www.dreamstime.com/cute-deer-turning-side-tongue-out-cute-deer-turning-side-tongue-out-forest-beautiful-image183839472

DISCUSSION

I began with an impression that impalas are peculiarly inclined to protrude the tongue.

However, the puzzle has shifted, in view of similar, seemingly gratuitous, protrusion in many other bovids and cervids.

This has emphasised, for me, how important search-images are in Science.

Now, the main questions seem to be:

  • why is it that pigmentation of the tongue is apparent only in bovids and giraffids, not in cervids? and
  • why is the tongue so dark-pigmented in impalas, given that one of their peculiarities is that they do not extend the tongue in either foraging or grooming?
הועלה ב-פברואר 21, 2024 10:57 אחה"צ על ידי milewski milewski | 8 תגובות | הוספת תגובה

פברואר 16, 2024

How do hippotragin bovids bite?

We do not normally regard ruminants as biting animals.

However, there is an intriguing possibility that the roan antelope (Hippotragus equinus) bites injuriously in self-defence.

The reasons why ruminants are associated with biting in self-defence are that they

  • have horns or antlers, plus hooves, all potentially effective as weapons,
  • lack canine teeth in most species, even in males,
  • lack upper incisors, which means that any 'bite' by means of the lower incisors would be relatively harmless, and
  • in the case of several clades, have gapes so tight that defensive biting by means of the premolars is impossible.

The domestic goat (Capra hircus) is known to bite humans. However, as far as I know it does so by means of its lower incisors, which are limited by the absence of upper incisors.

Hippotragus spp. have a reputation for pugnaciousness, both intraspecifically and anti-predator.

It is usually assumed that this involves only the horns. However, footage of a mature male individual of the sable antelope (Hippotragus niger niger) standing its ground against a group of the African hunting dog (Lycaon pictus) shows that the forehooves are flailed threateningly. And there is mention in the literature of the roan antelope (Hippotragus equinus) biting attackers.

What seems previously to have been overlooked is that hippotragins differ from most other bodies in that they possess a stretchy gape, allowing the biting off of fibrous food items such as grass culms. Unlike alcelaphins (all of which have tight gapes), hippotragins rely on plant matter some distance above the ground, not normally grazing on lawns.

The stretchy gape of hippotragins also allows the abrasion of bones in the mouth in osteophagy, a practice particularly frequent in this tribe owing to its tendency to occur on nutrient-poor substrates.

The stretchy gape of hippotragins is evident as a 'perverse smile' when the animals breathe heavily while running under duress.

הועלה ב-פברואר 16, 2024 11:21 אחה"צ על ידי milewski milewski | 0 תגובות | הוספת תגובה

A comparison between impalas (Aepyceros) of Africa and the blackbuck (Antilope cervicapra) of India

Impalas (Aepyceros) of southern and East Africa resemble - at least superficially - the blackbuck (Antilope cervicapra) of India.

BODY MASS

Impalas are more massive than the blackbuck, somewhat undermining the validity of the comparison.

Furthermore, sexual dimorphism is less in impalas than in the blackbuck.

GAITS AND POSTURES

The normal walking gait in both cases is the amble.

In the blackbuck alone, mature males, in rivalry and courtship, use an exaggerated amble (which is actually more extreme than the walking gait of Giraffa).

In both genera, fleeing from predators includes spectacular bounding, as well as galloping (https://stock.adobe.com/search?k=impala+jumping&asset_id=270207382).

Despite their similarity in bounding, the two genera differ considerably in their behaviour towards fences.

Impalas are surprisingly reluctant to jump over high fences, but are somewhat erratic, so that game ranchers confine them by means of fences 2.4 metres high. The blackbuck is decidedly reluctant to jump over even low fences (https://blog.bookyourhunt.com/impala-hunting-in-southern-and-eastern-africa/ and https://highlandswilderness.net/fencing/).

Impalas are peculiar in not trotting, whereas the blackbuck - like all other gazelles - habitually trots (check).

Impalas have a kick-stotting gait (https://www.alamy.com/stock-photo-impala-jumping-through-the-air-31802663.html?imageid=4153A7B3-C185-4EB7-AEAE-BE8EDEE68EE9&p=34420&pn=1&searchId=afe5e634cabb36b932797102a2dfbc29&searchtype=0), whereas the stotting gait of the blackbuck is similar to that of diverse other ruminants.

Impalas swim poorly, whereas the blackbuck swims competently, like other gazelles (https://www.facebook.com/watch/?v=464324768942915).

Neither impalas nor the blackbuck use bipedal postures to forage.

Both genera lie by means of sternal recumbency. However, impalas, in adulthood, tend to lie mainly at night. By day they ruminate while standing (https://www.pond5.com/stock-footage/item/138472590-impala-swallowing-food-and-regurgitating-cud-addo-national-p).

ADAPTIVE COLOURATION

In both cases, the ground-colour is medium-tone, with horizontal panelling on the flanks and crisply-defined white countershading in the ventral part of the torso.

However, a major difference is that duly males differ from adult females in the blackbuck.

SOCIOSEXUAL BEHAVIOUR

GREGARIOUSNESS

Impalas are more gregarious than is the blackbuck. This is evidenced by the fact that founder populations of the former, e.g. in reintroduction programs, tend to fail unless several dozen individuals are present, whereas in the case of the latter only a few individuals are necessary. The two genera fare differently in captivity (e.g. in zoos) accordingly.

Texas introductions

ANTI-PREDATOR STRATEGIES

RELATIONSHIP TO PARASITES

הועלה ב-פברואר 16, 2024 04:27 לפנה"צ על ידי milewski milewski | 5 תגובות | הוספת תגובה

פברואר 15, 2024

Can precociality in the colouration of impalas (Aepyceros) be explained by their confusing nature as 'sedentary plains game'? part 2

...continued from https://www.inaturalist.org/journal/milewski/89704-can-precociality-in-the-colouration-of-impalas-aepyceros-be-explained-by-their-confusing-nature-as-sedentary-plains-game-part-1#

PATTERN ON BUTTOCKS (https://www.gettyimages.com.au/detail/photo/distinctive-black-markings-of-an-impala-aepyceros-royalty-free-image/938419410?phrase=african+impala&adppopup=true) :

The pattern on the buttocks hypothetically functions disruptively, i.e. in alignment with camouflage rather than advertisement.

This pattern - although individually variable - is one of the less precocial of the features of colouration in impalas.

https://www.gettyimages.com.au/detail/photo/instinct-royalty-free-image/975807822?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/impala-calf-in-the-wilderness-of-africa-royalty-free-image/1206539786?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/impala-female-with-lamb-urinating-royalty-free-image/57079600?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/impalas-okavango-delta-botswana-royalty-free-image/1457505003?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/impalas-okavango-delta-botswana-royalty-free-image/1457504436?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/impalas-young-animals-south-luangwa-national-park-royalty-free-image/927949292?phrase=african+impala&adppopup=true

CAUDAL FLAGS:

Caudal flags in impalas hypothetically function mainly sociosexually.

The tail of impalas is similar in infants and adults (https://www.shutterstock.com/image-photo/female-impalas-serengeti-national-park-tanzania-1080255455 and https://www.gettyimages.com.au/detail/photo/wild-impala-at-a-tourist-game-park-in-south-africa-royalty-free-image/1269577880?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/exuberant-baby-impala-royalty-free-image/589147925?phrase=african+impala&adppopup=true).

As in adults, the tail is habitually tucked.

The stalk of the tail is slightly broader than in adults, proportionately to body size. The bare skin of the perineum is, accordingly, not fully pigmented in infants (https://www.gettyimages.com.au/detail/photo/impala-calf-in-the-wilderness-of-africa-royalty-free-image/1207634985?phrase=african+impala&adppopup=true).

Infants cannot be said to possess any caudal flags beyond the penicillate caudal flag (https://www.alamy.com/stock-photo-kasane-botswana-chobe-national-park-impala-aepyceros-melampus-90486443.html?imageid=894170E9-599D-4494-8378-B4E7151877AC&p=14406&pn=2&searchId=3fc36c460518a6c89b8f9aedb0b7c60c&searchtype=0).

This is because the versatility of piloerection of the jointed feather-tassel/plume-tassel is not expressed in infancy. However, further study is needed of infants engaging in playful kick-stotting.

The following show that, in impalas, the tail is displayed by infants/juveniles during suckling:

https://www.gettyimages.com.au/detail/photo/impalas-female-with-young-suckling-maasai-mara-royalty-free-image/993497958?adppopup=true

https://www.inaturalist.org/observations/10506367

https://www.inaturalist.org/observations/10504079https://www.inaturalist.org/observations/197703501

https://www.inaturalist.org/observations/197638270https://www.inaturalist.org/observations/178549792

https://www.inaturalist.org/observations/169814268

https://www.offset.com/photos/impala-aepyceros-melampus-and-calf-masai-mara-national-park-kenya-1017898

https://www.dreamstime.com/stock-photo-two-impalas-mother-baby-tarangire-tanzania-africa-image98512874

https://www.dreamstime.com/impala-aepyceros-melampus-female-young-suckling-masai-mara-park-kenya-impala-aepyceros-melampus-image172747402

https://www.dreamstime.com/stock-photo-baby-impala-his-mother-young-suckling-s-grassland-africa-image42932433

https://www.dreamstime.com/impala-aepyceros-melampus-female-young-suckling-masai-mara-park-kenya-image196305825

Aepyceros petersi: https://cdstar.shh.mpg.de/bitstreams/EAEA0-14BD-D4A7-7F3C-0/full.jpg

BUCCAL SEMET:

The buccal semet of impalas hypothetically functions to accentuate the movements of the mouth in rumination and grooming. This would facilitate gregarious vigilance.

This semet is exceptionally uniform among individuals, sexes, ages, and species of impalas.

The buccal semet is fully precocial (https://www.gettyimages.com.au/detail/photo/profile-of-impalas-south-africa-royalty-free-image/86082185?phrase=african+impala&adppopup=true and https://www.dreamstime.com/stock-image-impala-wildlife-background-africa-double-drink-ewes-water-unison-as-seen-wilds-image35334661).

The pattern of colouration at and around the mouth is complete at birth (https://www.dreamstime.com/impala-antelope-wilderness-africa-image174751963 and https://www.gettyimages.com.au/detail/photo/lion-kills-baby-impala-okavango-delta-royalty-free-image/1457558393?phrase=african+impala&adppopup=true).

DISCUSSION

Impalas are unusual among ruminants in that their colouration at birth is similar to that in masculine maturity (https://www.gettyimages.com.au/detail/photo/an-impala-and-young-calf-aepyceros-melampus-on-the-royalty-free-image/1248752401?phrase=african+impala&adppopup=true).

This is the result of both

  • the sexual monomorphism of impalas, in which males are similar to females in colouration despite possessing head adornments categorically absent from females, and
  • the precociality of impalas, which exceeds that of other 'cover-dependent' bovids as well as Cervidae in general.

This precociality is particularly noteworthy in the case of the pedal flag.

This is because the pedal flag is configured to function only in vegetation so short that the pasterns are fully visible.

This seems antithetical to the idea of infants hiding, by lying flat under cover, as happens in many spp. of ruminants.

Various spp. of 'plains game' are similar to impalas in forming 'creches' (https://www.gettyimages.com.au/detail/news-photo/group-of-impalas-with-babies-in-the-manyeleti-reserve-in-news-photo/1200173209?adppopup=true and https://www.gettyimages.com.au/detail/photo/impala-antelope-in-akagera-national-park-rwanda-royalty-free-image/1226040651?phrase=african+impala&adppopup=true).

However, all of the other creche-forming spp. (e.g. Taurotragus oryx pattersonianus, Hippotragus equinus equinus, ?Damaliscus lunatus jimela) have infantile colouration different from that of mature males.

This 'intricate uniformity' seems consistent with the idea of 'gregarious camouflage' in impalas (https://www.gettyimages.com.au/detail/photo/adorable-herd-of-female-impala-in-tight-group-at-royalty-free-image/1256116639?phrase=african+impala&adppopup=true and https://www.gettyimages.com.au/detail/photo/female-impala-harem-royalty-free-image/1182461957?phrase=african+impala&adppopup=true).

הועלה ב-פברואר 15, 2024 11:59 לפנה"צ על ידי milewski milewski | 19 תגובות | הוספת תגובה

פברואר 11, 2024

Can precociality in the colouration of impalas (Aepyceros) be explained by their confusing nature as 'sedentary plains game'? part 1

@adamwelz @syddddney

INTRODUCTION

The basic nature of impalas (Aepyceros) has been confusing for naturalists.

This is possibly because it has not been fully realised that impalas are 'plains game turned sedentary'.

In this Post, I explain the adaptive colouration of infants in this context.

IMPALAS AS DECEPTIVE 'PLAINS GAME'

The rationale goes as follows.

Impalas are associated with woody cover, rather than treeless grassland.

However, they conform with large ungulates of open, short vegetation in

At the same time, impalas differ from most other 'plains game' in a basic way, viz. in not being migratory/nomadic.

Instead, throughout their range, they are thoroughly sedentary (https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2028.1982.tb00301.x and https://www.researchgate.net/publication/230185512_Home_range_dispersal_and_the_clan_system_of_impala).

Impalas achieve this sedentariness by resorting in the dry season to foods other than grass, particularly

What this means is that the well-known association of impalas with trees and shrubs may be misleading. Their 'cover-dependence' is trophic (https://www.vocabulary.com/dictionary/trophic), rather than anti-predatory.

Unlike reduncins (https://en.wikipedia.org/wiki/Reduncinae) and tragelaphins (https://en.wikipedia.org/wiki/Tragelaphini) of similar body size, impalas are not 'cover-dependent' w.r.t. predators.

Instead, impalas are typical of 'plains game' in their

  • reliance on gregarious vigilance,
  • diurnal rather than nocturnal foraging, drinking, and parturition,
  • extreme gaits in reaction to predators, and
  • abandonment of concealment - even as infants.

Essentially, impalas have made a tradeoff, paying the costs (downsides) of certain benefits (upsides).

The main upside is the food provided by woody plants, obviating the need to shift location.

However, the main downsides are that

  • these plants provide cover not for the impalas, but for their predators, and
  • sedentariness exacerbates parasitism by ticks, mites, and flies.

The result of the unusual ecological strategy of impalas is a combination of biological traits that has confused naturalists in the past.

In this Post, I focus on only part of this confusion: that regarding adaptive colouration, and how it changes - or, more precisely, hardly changes - from youth to maturity.

ADAPTIVE COLOURATION RELATIVE TO TYPICAL 'PLAINS GAME'

The above characterisation provides a basis for assessing the adaptive colouration of infants in impalas.

In particular, it offers insight into their surprising emancipation from cover-dependence.

Unlike most 'plains game', adults of impalas do not have adaptively conspicuous colouration. I refer to dark/pale features so bold that they advertise the figures at distance.

Instead, their colouration is configured differently from both

RELEVANT FEATURES OF COLOURATION IN INFANTS, as per https://www.inaturalist.org/journal/milewski/89191-bleezes-flags-and-semets-in-the-adaptive-colouration-of-impalas-aepyceros-part-1#

Throughout this Post, I refer to Aepyceros melampus and Aepyceros petersi jointly, except where specified.

Infants of impalas have colouration similar to that of their mothers and fathers (https://www.gettyimages.com.au/detail/photo/impala-and-fawn-royalty-free-image/1219697789?phrase=african+impala&adppopup=true).

Impalas are unusual among the relatively large-bodied (body mass 50 kg or more) ungulates of the world - including most spp. of 'plains game' - in a certain way.

This is that the colouration of mature males is approximately complete already at birth, at least w.r.t. pigmentation, as opposed to sheen.

In other words, the pattern of pigmentation of the pelage in impalas is remarkably precocial.

However, not all features of colouration are equally well-developed in neonates.

Thus, a subsidiary aim of this Post is to document and illustrate these minor chronological (= ontogenetic) variations.

LATERAL FLAG:

The lateral flag hypothetically facilitates the gregariousness of impalas, dependent on certain conditions of illumination.

This flag is undeveloped (i.e. present only in incipient form) in infants (https://www.alamy.com/stock-photo-three-impala-walking-along-in-warm-lighting-18765797.html?imageid=4BAAA4C2-8374-4CA7-BCE5-788C0800662B&p=34420&pn=2&searchId=97e69abec044f22cfa320b375090cc9f&searchtype=0 and https://www.shutterstock.com/image-photo/female-impala-her-calf-kruger-national-1453377443 and https://www.alamy.com/impala-ewe-with-calf-aepyceros-melampus-okonjima-nature-reserve-namibia-africa-image230532633.html?imageid=75A1E27D-EC24-4482-98B2-1A80F2C9DB47&p=71799&pn=1&searchId=f389d6fe91e8459064d1ae8d87ceca96&searchtype=0 and https://wildadventuresblog.files.wordpress.com/2023/11/rixaka-and-baby-impala-1.jpg).

This is in contrast to the pedal flag (see below).

In particular, the sheen effect is absent in infancy from the relatively pale panel on the flanks (https://www.gettyimages.com.au/detail/photo/impalas-mother-and-young-aepyceros-melampus-royalty-free-image/128112952?phrase=african+impala&adppopup=true).

The following shows that, when the sheen effect is 'switched off', adults resemble infants in that the pattern on the flanks is subdued (https://www.gettyimages.com.au/detail/photo/impala-in-rain-storm-lake-nakuru-kenya-royalty-free-image/126377157?phrase=african+impala&adppopup=true).

On balance, the lateral flag is among the least precocial of the patterns described in this Post. However, it appears after only about one month of age (https://www.alamy.com/stock-photo-africa-kenya-masai-mara-national-reserve-young-impalas-walking-aepyceros-42109588.html?imageid=143E541A-8495-4DA2-A237-1CBED6420840&p=147756&pn=6&searchId=0171166ff0fdcc816dc79c8195263b39&searchtype=0).

https://www.mindenpictures.com/stock-photo-impala-aepyceros-melampus-mother-running-with-her-calf-following-naturephotography-image00630132.html

https://www.dreamstime.com/impala-lamb-masai-mara-national-reserve-young-aepyceros-melampus-kenya-image243636698

https://www.offset.com/photos/an-impala-and-young-calf-aepyceros-melampus-on-the-edge-of-woodland-963170

https://www.superstock.com/asset/impala-calf-baby-impala-antelope-wilderness-africa/6001-16208619

https://www.inaturalist.org/observations/4425491 and https://www.africanflyingadventures.com/life-and-death-in-the-bush-impala/

https://www.gettyimages.com.au/detail/photo/portrait-of-deer-standing-on-field-kruger-national-royalty-free-image/1425287723?adppopup=true)

https://www.gettyimages.com.au/detail/photo/impalas-female-with-young-animals-in-the-steppe-royalty-free-image/927944266?phrase=african+impala&adppopup=true

It is possible that the difference between infants and adults, in the expression of the lateral flag, is owing largely to the proportional 'filling out' of the torso, as the animal progresses from milk to a bulky diet of grass.

ANTERIOR AURICULAR FLAG:

The anterior auricular flag is hypothetically an anti-predator adaptation. It emphasises communication to the predator that it has been spotted, and has lost the advantage of surprise.

The anterior auricular flag of impalas is complete in infants (https://www.alamy.com/young-animal-botswana-chobe-national-park-impala-aepyceros-melampus-savute-bush-daytime-wildlife-tourism-nature-no-people-outdoors-safari-young-animals-cute-animals-in-the-wild-big-5-animal-calf-africa-image595891120.html?imageid=1355A1C6-6044-4D46-BD19-D855A978C069&p=2325997&pn=1&searchId=2c70548f127dc53b817942155023dd85&searchtype=0 and https://www.shutterstock.com/image-photo/impala-family-nakuru-national-park-368215919). This precociality exceeds that of the dark stripes on the buttocks.

https://www.alamy.com/stock-photo-two-baby-impala-antelopes-in-the-african-bush-29057562.html

https://www.dreamstime.com/royalty-free-stock-photo-impala-antelope-lambs-two-small-aepyceros-melampus-lake-nakuru-national-park-kenya-image40154625

https://www.gettyimages.com.au/detail/photo/impala-with-her-young-aepycaros-melampus-masai-mara-royalty-free-image/57255400?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/aepyceros-melampus-female-with-young-ndutu-tanza-royalty-free-image/90062064?phrase=african+impala&adppopup=true

POSTERIOR CORONAL FLAG:

The posterior coronal flag hypothetically facilitates gregarious vigilance in impalas.

It is located on the highest part of the figure, and emphasise the orientation of attention/alarm, particularly as individuals raise their heads from foraging.

This is illustrated in the opening footage in https://www.google.com.au/search?q=Impala+jumping+fence+on+game+ranch&sca_esv=85ac6a756d1f0a52&sxsrf=ACQVn0-8qDhHDaQQj4ijdrqeQi9DmroxJw%3A1708062330222&ei=evbOZc2YDfLvseMPytGE2A8&ved=0ahUKEwjNvcmDlK-EAxXyd2wGHcooAfsQ4dUDCBA&uact=5&oq=Impala+jumping+fence+on+game+ranch&gs_lp=Egxnd3Mtd2l6LXNlcnAiIkltcGFsYSBqdW1waW5nIGZlbmNlIG9uIGdhbWUgcmFuY2gyCBAAGIAEGKIEMggQABiABBiiBEijD1C0DFi0DHACeACQAQCYAd8BoAHfAaoBAzItMbgBA8gBAPgBAcICDhAAGIAEGIoFGIYDGLADiAYBkAYC&sclient=gws-wiz-serp#fpstate=ive&vld=cid:f7bf2184,vid:ueMZh53DSBY,st:0.

Infants tend not to show the posterior coronal flag, even when the associated adults do show it (https://www.alamy.com/baby-impala-with-mom-cute-impala-calf-image334465986.html?imageid=39ACF71F-D5CD-499A-B7CD-32669CF8CF74&p=1760945&pn=13&searchId=d273b17bcb1f0d1c84c7995c6c50d374&searchtype=0 and https://www.alamy.com/baby-impala-with-mom-cute-impala-calf-image334466064.html?imageid=14A68E2E-F5DA-4EB0-9841-8D17885FEF3A&p=1760945&pn=13&searchId=d273b17bcb1f0d1c84c7995c6c50d374&searchtype=0).

However, the posterior coronal flag may be more precocial than the lateral flag.

In the following, sheen has appeared on the posterior surface of the crown of the head, at an age too young for it to appear on the flanks of the torso.

https://www.dreamstime.com/royalty-free-stock-photos-antelope-image7622658

The following shows that a hair-whorl (https://en.wikipedia.org/wiki/Hair_whorl) - which may perhaps help to explain the sheen effect - occurs at the location of the posterior coronal flag.

https://www.gettyimages.ie/detail/photo/the-small-horns-of-a-young-male-impala-royalty-free-image/617783819?phrase=impala+the+animal&adppopup=true

The following show the posterior coronal flag in adults. A main point to note is that, although there is a definite pattern on the buttocks, it is the pallor (owing to sheen) on the posterior surface of the crown that renders the figures conspicuous.

https://www.shutterstock.com/image-photo/herd-female-impala-serengeti-national-park-1895436763

https://www.shutterstock.com/image-photo/herd-impala-aepyceros-melampus-timbavati-game-2207433769

https://www.dreamstime.com/impala-aepyceros-melampus-kruger-national-park-mpumalanga-south-africa-image135031275

PEDAL FLAG:

The pedal flag hypothetically facilitates gregariousness, particularly at night, when impalas tend to congregate on lawns.

This flag is peculiarly precocial (https://www.dreamstime.com/stock-photo-young-impala-baby-stands-watching-other-antelopes-game-reserve-south-africa-image70429327).

It is fully developed in infants, despite

  • the lack of sheen elsewhere on the pelage of infants, and
  • the expectation that the metatarsal glands are relatively poorly-developed at birth.

https://www.dreamstime.com/common-impala-calf-walks-stony-track-image260101943 and https://www.dreamstime.com/common-impala-calf-stands-stony-track-image260102489 and https://www.dreamstime.com/baby-common-impala-walks-along-dirt-track-image257794099

https://www.inaturalist.org/observations/165329533

https://www.inaturalist.org/observations/142346786

https://www.inaturalist.org/observations/106255260

https://www.inaturalist.org/observations/9839721

https://www.inaturalist.org/observations/9356668

to be continued in https://www.inaturalist.org/journal/milewski/89824-can-precociality-in-the-colouration-of-impalas-aepyceros-be-explained-by-their-confusing-nature-as-sedentary-plains-game-part-2#...

הועלה ב-פברואר 11, 2024 01:11 לפנה"צ על ידי milewski milewski | 51 תגובות | הוספת תגובה

פברואר 10, 2024

Bleezes, flags, and semets in the adaptive colouration of impalas (Aepyceros), part 2

...continued from https://www.inaturalist.org/journal/milewski/89191-bleezes-flags-and-semets-in-the-adaptive-colouration-of-impalas-aepyceros-part-1#

CAUDAL FLAGS:

Penicillate caudal flag:

The long white hairs of the tail of impalas are normally hidden, partly because they are folded and partly because the tail is tucked (https://www.gettyimages.com.au/detail/photo/leaping-impala-chobe-national-park-botswana-royalty-free-image/538630239?adppopup=true).

However, the long white hairs are exposed in several situations, viz.- when the tail is swished to shoo insects,

  • during micturition and defecation, and
  • by infants and juveniles during suckling.

In all these cases, the distal 'joint' on the tail is unfolded, extending the white tip, but the lateral hairs remain folded. This is what I call a 'penicillate' pattern (https://www.alamy.com/stock-photo-impala-male-aepyceros-melampus-cape-s-africa-12936370.html?imageid=A1D1CBEE-FAD2-4524-B369-BE802AB25F31&p=27299&pn=10&searchId=422524482389f4d1898ffb44225a4ddf&searchtype=0).

The following, of Aepyceros petersi, show how piloerection transforms the appearance of the tail in impalas:

https://www.dreamstime.com/amber-black-white-coloring-adult-male-impala-its-curved-horns-pondering-distance-tarangire-national-image134936351

https://www.inaturalist.org/observations/11072572https://www.inaturalist.org/observations/500032

Laterally-piloerected caudal flag:

The long white hairs are laterally piloerected during masculine display.

In Aepyceros melampus, which possesses a relatively small tail with a jointed feather-tassel, this gives the tail a shape resembling that of a symmetrical feather (https://www.alamy.com/stock-photo-impala-buck-with-tail-raised-and-making-sounds-territorial-behavior-48376563.html and https://www.dreamstime.com/male-impala-botswana-aepyceros-melampus-savuti-region-northern-africa-image190060019 and https://www.dreamstime.com/stock-photo-impala-male-bellowing-territorial-snorting-growling-roaring-exciting-his-harem-females-rutting-time-image84208595 and https://matirasafari.com/wp-content/uploads/2017/12/ME8A3771m.jpg).

In Aepyceros petersi, which possibly possesses a relatively large tail with a plume-tassel, the shape is fluffy rather than fan-like.

https://www.inaturalist.org/observations/197926724

https://www.inaturalist.org/observations/3431525

https://www.inaturalist.org/observations/6901419

https://www.inaturalist.org/observations/11238746

I have yet to see the laterally-piloerected caudal flag activated in females or juveniles. Females sometimes piloerect laterally while keeping the tail tucked. However, this does not have a conspicuous effect, partly because the spread long hairs - for some strange reason - do not appear white.

Vertically-piloerected caudal flag:

During kick-stotting, a shape reminiscent of a butcher's cleaver results from

  • flexing of the distal 'joint' to a right-angle, and
  • piloerection of the lateral long white hairs in a ventral, not lateral, orientation, so that the tracts on left and right sides of the tail converge into a blade-like surface.

https://www.alamy.com/impala-black-faced-aepyceros-melampus-jumping-high-etosha-national-park-namibia-africa-image440466092.html?imageid=50688ED7-5A71-4DC9-93F7-CB9731215001&p=2206959&pn=5&searchId=a128d0b9ff98444a3d95336675cd8ddb&searchtype=0

https://www.gettyimages.com.au/detail/photo/sprinting-impala-royalty-free-image/503017078?adppopup=true

https://www.inaturalist.org/observations/3739299

I am unsure whether mature males activate the vertically-piloerected caudal flag, even during kick-stotting.

BUCCAL SEMET:

The complex pattern on the chin, mandibles, and lips is small-scale, but crisply-defined, individually consistent, and different from that in any other ungulate,

This hypothetically functions to accentuate

This hypothetically facilitates social monitoring and gregarious vigilance.

A puzzling aspect of the colouration around the mouth, in impalas, is that the upper lip appears noticeably white only when viewed from the front, not in profile. This, like several other pale features in impalas, seems to reflect subtle and peculiar sheen-effects.

https://www.alamy.com/stock-photo-impala-aepyceros-melampus-oxpecker-sitting-on-impala-zimbabwe-76014030.html?imageid=C1520A05-D492-404D-B60C-2A0FA8F8FEF4&p=851480&pn=1&searchId=2c70548f127dc53b817942155023dd85&searchtype=0

https://www.dreamstime.com/royalty-free-stock-images-impala-image13351309

https://www.inaturalist.org/observations/9634

https://www.dreamstime.com/stock-photography-impala-wildlife-background-africa-fun-nature-ewe-chews-open-mouth-creating-image-humor-as-seen-image35412872

https://www.dreamstime.com/portrait-cute-wild-young-male-impala-aepyceros-melampus-nature-reserve-mara-north-conservancy-kenya-wildlife-image132878721

https://www.inaturalist.org/observations/10945099

https://www.alamy.com/impala-aepyceros-melampus-males-grooming-each-other-masai-mara-game-reserve-kenya-image262977047.html?imageid=C51F55F6-CE52-442E-AA83-3FAB2C5685D1&p=269351&pn=10&searchId=f88dac56b555417b6a06fa62b13fef50&searchtype=0

https://www.dreamstime.com/impala-black-faced-aepyceros-melampus-petersi-vrouwtje-close-up-kop-namibie-female-head-namibia-image129027529

https://www.alamy.com/stock-photo-blacked-faced-impala-or-black-faced-impala-aepyceros-melampus-petersi-74749154.html?imageid=CD8484B4-2478-4391-95D2-922B44C90F13&p=183828&pn=2&searchId=1f5542e7213ab29c0373963d6ec132b5&searchtype=0

https://www.dreamstime.com/stock-photo-black-faced-impala-etosha-national-park-namibia-image-image90011717

https://www.dreamstime.com/female-impala-aepyceros-melampus-portrait-kruger-national-park-south-africa-female-impala-aepyceros-melampus-portrait-kruger-image270426491

https://www.dreamstime.com/female-impala-aepyceros-melampus-portrait-kruger-national-park-south-africa-female-impala-aepyceros-melampus-portrait-kruger-image270426509

https://www.dreamstime.com/female-impala-aepyceros-melampus-portrait-kruger-national-park-south-africa-female-impala-aepyceros-melampus-portrait-kruger-image269672636

https://www.dreamstime.com/female-impala-aepyceros-melampus-portrait-kruger-national-park-south-africa-female-impala-aepyceros-melampus-portrait-kruger-image269672639

https://www.dreamstime.com/female-impala-aepyceros-melampus-portrait-kruger-national-park-south-africa-female-impala-aepyceros-melampus-portrait-kruger-image270428736

https://www.dreamstime.com/common-impala-kruger-national-park-south-africa-three-red-billed-oxpecker-grooming-common-impala-kruger-national-park-south-image291301703

https://www.dreamstime.com/stock-photo-fighting-impalas-image12091830

https://www.dreamstime.com/stock-photo-small-herd-antilopes-tarangire-tanzania-africa-image98512881

Gular semet:

There is a whitish patch at the crook-of-throat (https://www.dreamstime.com/stock-photo-impala-savanna-national-reserved-south-africa-kenya-image40584100 and https://www.inaturalist.org/observations/197961307 and https://www.alamy.com/stock-photo-black-faced-impala-portrait-of-careful-grazing-antelope-eating-tiny-52966912.html?imageid=6B3C7657-DF3E-4C77-8C06-E2909124802F&p=5021&pn=3&searchId=a5b956efd11b804f1481dd41761ad956&searchtype=0), which can be somewhat conspicuous in the limited context of masculine display, particularly roar-grunting (https://www.youtube.com/watch?v=IqzBw9EWhjU).

This patch is particularly noticeable in masculine maturity, relative to females and juveniles, because

  • the throat is broadened, and
  • the ground-colour of the neck is somewhat darkened.

However, the case for a gular semet is weakened by the facts that

  • the pale feature in question is individually variable, rather than sexually dimorphic, and
  • females do not have noticeable vocalisations.

https://www.alamy.com/stock-photo-male-black-faced-impala-challenging-another-male-in-the-etosha-national-138416866.html?imageid=D3A1E078-4C32-42EE-AF5A-0E3ED604E3FB&p=298586&pn=7&searchId=ae880af1fd61c0455cbecb5723d2b621&searchtype=0

https://www.dreamstime.com/impala-savanna-national-reserved-south-africa-kenya-animal-habitat-wildlife-scene-nature-image175021430

https://walkthewilderness.net/animals-of-africa-dominant-impala-behavior/

https://www.alamy.com/impala-aepyceros-melampus-young-male-grooming-a-female-nakuru-national-park-kenya-africa-image262992215.html?imageid=64908F75-77ED-426C-A7BB-D4C5258DF1F9&p=215444&pn=12&searchId=7dc11c78361bd5df1ff35974e5ef97a8&searchtype=0

https://www.dreamstime.com/stock-photos-male-impala-flehman-responce-image15033143

https://www.dreamstime.com/royalty-free-stock-photo-impala-showing-flehman-responce-botswana-image15518765

AURICULAR SEMETS:

A noteworthy aspect of the adaptive colouration of impalas is that there are no auricular semets (https://www.inaturalist.org/posts/55694-ten-best-illustrations-of-auricular-semets-in-deer# and https://www.inaturalist.org/posts/55639-auricular-semets-in-alces-and-odocoileus-but-not-other-odocoileine-deer# and https://www.inaturalist.org/journal/milewski/55532-previously-overlooked-facial-expressions-in-the-wapiti#).

DISCUSSION

The overall colouration of impalas is puzzling, because it conforms to neither crypsis nor camouflage (https://www.gettyimages.ie/detail/photo/impalas-in-south-africa-royalty-free-image/1187648715?phrase=impala+the+animal&adppopup=true and https://www.gettyimages.ie/detail/photo/impala-and-kudu-in-south-africa-royalty-free-image/1185776039?phrase=impala+the+animal&adppopup=true and https://www.gettyimages.com.au/detail/photo/giraffes-walking-to-the-forest-royalty-free-image/836319922?phrase=african+impala&adppopup=true).

A case could be made that the overall colouration of impalas functions as 'gregarious camouflage' (https://www.dreamstime.com/impala-aepyceros-melampus-impala-aepyceros-melampus-small-fast-antelope-african-savanna-tsavo-national-park-taita-hills-image111661427 and https://www.dreamstime.com/stock-image-herd-impala-aepyceros-melampus-image40133771 and https://www.dreamstime.com/herd-alert-female-impala-looking-camera-okavango-delta-botswana-herd-alert-female-impala-botswana-image129682758 and https://www.gettyimages.ie/detail/photo/herd-of-impalas-royalty-free-image/148092452?phrase=impala+the+animal&adppopup=true and https://www.gettyimages.com.au/detail/photo/herd-of-female-impala-botswana-africa-royalty-free-image/142025793?phrase=african+impala&adppopup=true and https://www.gettyimages.com.au/detail/photo/herd-of-impala-aepyceros-melampus-against-a-green-royalty-free-image/1313472400?phrase=african+impala&adppopup=true).

In 'gregarious camouflage', the disruptive patterns of colouration function

  • relative to other members of the group, as opposed to the background/vegetation, and
  • without the need to be stationary, or to 'freeze' in alarm.

https://www.gettyimages.com.au/detail/photo/herd-of-impalas-in-wilderness-royalty-free-image/561426203?phrase=african+impala&adppopup=true and https://www.gettyimages.com.au/detail/photo/impalas-royalty-free-image/561426993?phrase=african+impala&adppopup=true and https://www.gettyimages.com.au/detail/photo/impala-herd-royalty-free-image/561427575?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/news-photo/impala-aepyceros-melampus-herd-of-females-in-grass-alert-to-news-photo/578257132?adppopup=true

https://www.gettyimages.com.au/detail/photo/herd-of-impalas-and-plains-zebras-royalty-free-image/534980932?phrase=african+impala&adppopup=true

https://www.gettyimages.com.au/detail/photo/male-impalas-and-topi-royalty-free-image/519948262?phrase=african+impala&adppopup=true

The colouration on the back-of-ear of impalas is puzzling.

This because:
the blackish of the distal third (a broadly apical feature) would seem to accentuate the ear pinnae, but in reality falls short of conspicuousness, because the rest of the posterior surface of the ear pinnae is not pale enough.

It is true that the dark marking on the back-of-ear is close enough to the sheeny crown to produce some tenuous dark/pale contrast. However, the puzzle remains of why the proximal two-thirds of the back-of-ear lack a significant sheen-effect (https://www.gettyimages.ie/detail/photo/high-angle-view-of-goats-walking-on-field-royalty-free-image/1306773451?phrase=impala+the+animal&adppopup=true and https://www.gettyimages.ie/detail/photo/herd-of-female-impala-in-serengeti-national-park-royalty-free-image/169566128?phrase=impala+the+animal&adppopup=true).

Why do impalas lack auricular semets, such as those seen in various genera of Cervidae?

The posterior coronal flag is one of the most unusual and subtle aspects of adaptive colouration in impalas. It is also the clearest example of the role of sheen in Aepyceros.

הועלה ב-פברואר 10, 2024 06:02 לפנה"צ על ידי milewski milewski | 24 תגובות | הוספת תגובה

פברואר 6, 2024

Gaits and anti-predator displays, compared between deer (Odocoileus) in North America and impalas (Aepyceros) in Africa

There is an adaptive trend among the ruminants of the world, as follows.

Species adapted to dense cover tend to have

  • inconspicuous colouration (particularly on the hindquarters),
  • a halting gait, viz. the semi-crosswalk,
  • a lack of stotting (strenuous displays of individual fitness, dissuasive to scanning predators), and
  • non-gregarious society.

A typical example is bushbucks (Tragelaphus, https://www.inaturalist.org/taxa/1431867-Tragelaphus-sylvaticus and https://www.inaturalist.org/taxa/42341-Tragelaphus-scriptus).

By contrast, species adapted to short, sparse vegetation tend to have

  • conspicuous colouration (particularly on the hindquarters),
  • a smooth gait, viz. the amble,
  • stotting, and
  • gregarious society.

A typical example is the springbok (https://www.inaturalist.org/taxa/42283-Antidorcas-marsupialis).

Intermediate species show intermediate traits.

In the context of this adaptive axis, certain anomalies emerge. The following are prime examples.

Deer of genus Odocoileus in North and central America, and impalas (Aepyceros) in southern and East Africa, are comparable. Both fall into the intermediate part of the axis described above.

Both are associated with some woody cover, as opposed to treeless grassland. Accordingly, both are somewhat gregarious.

Both have

  • medium body mass (about 50 kg),
  • unremarkable body-proportions, and
  • fairly nondescript colouration on forequarters and torso.

However, two incongruities emerge, as follows.

Firstly, Odocoileus deer combine

  • a halting walking gait, linked to cover-dependence and non-gregariousness, with
  • conspicuous colouration on the hindquarters, linked to open environments and gregariousness.

By contrast, impalas combine

  • a smooth walking gait, linked to open environments and gregariousness, with
  • inconspicuous colouration on the hindquarters, linked to cover-dependence and non-gregariousness.

Secondly, both genera have stotting displays. However, the gaits used are surprisingly different.

Odocoileus deer display by

By contrast, impalas display by

Stating the puzzle concisely:
The deer referred to are incongruently demonstrative, whereas impalas are incongruently non-demonstrative.

Before attempting to explain this puzzle, let us examine the evidence by means of photos/video clips.

The following show the semi crosswalk, which is

  • associated with cover-dependent ruminants, and
  • in the case of Odocoileus has been 'exaggerated' into demonstrative walking.

What is remarkable is that a halting gait, allowing the animal to 'freeze' with two legs in the air in order to blend into the background when hearing or seeing something suspicious, has been converted from an adaptation for concealment to an adaptation for advertisement. This has been done not by changing the footfall-sequence, but by exaggerating the lifting/lowering of the feet into conspicuous movements, probably together with release of odour from the pedal glands.

https://www.pond5.com/stock-footage/item/234025607-slow-motion-panning-shot-horned-whitetail-deer-walking-dry-g

https://www.pond5.com/stock-footage/item/246892228-white-tail-deer-walking-ridge-whitetail-deer-rut

https://www.pond5.com/stock-footage/item/150433074-whitetail-deer-casually-walking-sand-dunes

https://www.pond5.com/stock-footage/item/168721004-young-whitetail-deer-walking-snow

https://en.wikipedia.org/wiki/White-tailed_deer

https://www.youtube.com/watch?v=zADVhWj51Vg

https://www.youtube.com/watch?v=0FcWHBhqKkU

https://www.youtube.com/watch?v=KHxu7QxHmL4

https://www.youtube.com/watch?v=sxq09JUPh5s

https://www.youtube.com/watch?v=rmmpBklsfUY

https://www.youtube.com/watch?v=8XRhlvmAMpk

https://www.youtube.com/watch?v=F9DLRNhuXI4

https://www.google.com.au/search?q=Deer+walking+video&sca_esv=891f019e1683b014&tbm=vid&prmd=visnmbtz&sxsrf=ACQVn0-G_0CAbk7Lb86HWwd4dTBeYH4Pog:1707263962886&ei=2sfCZYHjNYiOseMP4I2QsAQ&start=10&sa=N&ved=2ahUKEwiBuK7w9ZeEAxUIR2wGHeAGBEYQ8tMDegQIEhAE&biw=986&bih=537&dpr=2.7#fpstate=ive&vld=cid:020b8d7b,vid:_9UiYWLW3aw,st:0

https://www.google.com.au/search?q=Deer+walking+video&sca_esv=891f019e1683b014&tbm=vid&prmd=visnmbtz&sxsrf=ACQVn0-G_0CAbk7Lb86HWwd4dTBeYH4Pog:1707263962886&ei=2sfCZYHjNYiOseMP4I2QsAQ&start=10&sa=N&ved=2ahUKEwiBuK7w9ZeEAxUIR2wGHeAGBEYQ8tMDegQIEhAE&biw=986&bih=537&dpr=2.7#fpstate=ive&vld=cid:668720a6,vid:r3qAhrvKi5I,st:0

https://www.google.com.au/search?q=Whitetail+Deer+walking+video&sca_esv=891f019e1683b014&biw=986&bih=537&tbm=vid&sxsrf=ACQVn0-5EbkeMDOORd0LiIOy4cwaUaaWrw%3A1707265476343&ei=xM3CZdbJFOv6seMP7qi6-Ak&ved=0ahUKEwjWu4TC-5eEAxVrfWwGHW6UDp84FBDh1QMIDQ&uact=5&oq=Whitetail+Deer+walking+video&gs_lp=Eg1nd3Mtd2l6LXZpZGVvIhxXaGl0ZXRhaWwgRGVlciB3YWxraW5nIHZpZGVvMggQABiABBiiBDIIEAAYgAQYogQyCBAAGIkFGKIEMggQABiABBiiBEjeK1AAWOMccAB4AJABAJgBhwKgAYUSqgEFMC4xLjm4AQPIAQD4AQHCAgcQABiABBgNwgILEAAYgAQYigUYhgPCAgcQIxiwAhgnwgIIECEYoAEYwwTCAgoQIRgKGKABGMME&sclient=gws-wiz-video#fpstate=ive&vld=cid:fc7401aa,vid:sXdOEAV_2w4,st:0

https://www.youtube.com/watch?app=desktop&v=VX1_gswmoew

https://www.pond5.com/stock-footage/item/65151043-whitetail-buck-deer-velvet-walking-down-river

הועלה ב-פברואר 6, 2024 11:44 אחה"צ על ידי milewski milewski | 98 תגובות | הוספת תגובה

פברואר 5, 2024

Stotting

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10498029/

https://www.projectnoah.org/spottings/8321330

https://www.sciencedirect.com/science/article/abs/pii/S0376635718300214

https://psycnet.apa.org/record/2007-03630-013

https://www.researchgate.net/figure/Number-of-trials-where-stotting-behavior-was-present-or-absent-partitioned-by-vegetation_tbl2_46511766

https://wildaboututah.org/follow-the-bouncing-deer/

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2656.2005.01014.x

https://www.pgmuseum.org/deer

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8372962/

https://www.jstor.org/stable/4535174

https://www.inaturalist.org/posts/76632-stotting-in-damaliscus

https://link.springer.com/article/10.1007/BF00299889

https://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=915

https://www.nwf.org/en/Educational-Resources/Wildlife-Guide/Mammals/Mule-Deer

https://www.washington.edu/news/2019/02/27/return-of-the-wolves-how-deer-escape-tactics-help-save-their-lives/

https://psycnet.apa.org/record/2007-03630-013

https://www.taylorfrancis.com/books/edit/10.1201/9781003354628/ecology-management-black-tailed-mule-deer-north-america-james-heffelfinger-paul-krausman?refId=a138049a-857b-4c21-82d0-18be4e881ecf&context=ubx

https://academic.oup.com/jmammal/article/89/3/636/861999?login=false

https://onlinelibrary.wiley.com/doi/10.1111/j.1439-0310.2008.01530.x

https://www.etsy.com/listing/1609357643/royalty-free-reference-image-for-artists

https://n1outdoors.com/whitetail-vs-mule-deer-differences/

https://i0.wp.com/scvnews.com/wp-content/uploads/2014/02/mule-deer-stotting.pg_.jpg

https://www.quora.com/Whats-the-difference-between-the-Sitka-black-tailed-deer-from-the-Alaskan-pan-handle-and-the-white-tailed-deer-found-in-Pennsylvania

https://www.producer.com/news/sheep-researchers-ask-for-deer-poop-2/

https://punchmagazine.com/hop-skip-jump-nature-photography/

https://www.flickr.com/photos/scattered/4118787442

https://www.bear-tracker.com/fawns.html

https://www.dreamstime.com/stock-photo-stotting-mule-deer-doe-running-all-four-feet-off-ground-image98265009

https://bcgforums.com/threads/baby-day-at-the-bison-range-mule-deer-fawn-stotting-and-red-dog-bison-calf.27521/

https://www.dreamstime.com/stotting-north-west-white-tailed-deer-odocoileus-virginianus-i-stotting-north-west-white-tailed-deer-odocoileus-virginianus-image106299321

https://johncarroutdoors.com/2021/03/19/published-photo-in-just-released-book/

https://sideriusblog.com/2013/05/04/to-stot-or-not-to-stot-the-mule-deer/

https://www.facebook.com/USFWS/photos/a.419357095774/10159526086900775/

https://gf.nd.gov/magazine/2022/nov/running-without-interruption

https://www.flickr.com/photos/scattered/4118018035

http://blog.kootenay-lake.ca/?p=1379

https://www.flickr.com/photos/pageworld/51722599625

https://upload.wikimedia.org/wikipedia/commons/d/d4/Stotting_mule_deer.jpg

https://www.alamy.com/a-black-tailed-deer-stotting-across-a-winter-field-image235857060.html

https://www.oklahoman.com/story/lifestyle/2021/11/29/what-stotting-and-why-do-mule-deer-do-it-northwestern-oklahoma/8659222002/

https://www.youtube.com/watch?v=h8DweS5Z684

https://www.youtube.com/watch?v=v1_qLKWeXPA

https://www.youtube.com/watch?v=ls2lmrmSQzA

https://petereades.photoshelter.com/image/I0000PVbRWhF5uYM

https://petereades.photoshelter.com/image/I000021Up4Tkw3LI

https://www.facebook.com/watch/?v=3443767672325312

https://www.istockphoto.com/photo/prairie-deer-saskatchewan-gm1953479708-557358161?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/black-tailed-mule-deer-odocoileus-hemionus-gm175224325-22633462?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/run-away-buck-gm1568260104-527735356?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/stag-deer-running-fast-across-dirt-road-gm1372645457-441704655?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/mule-deer-in-yellow-stone-gm1750423086-543753423?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/mule-deer-gm1467071727-498929924?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/mule-deer-gm1923040417-555492590?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/mule-deer-running-beside-harvested-field-in-montana-gm1297691491-390758660?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/mule-deer-doe-jump-run-gm172356051-4067117?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/young-buck-deer-in-central-montana-gm1361656244-433971994?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/colorado-wildlife-wild-deer-on-the-high-plains-of-colorado-gm1290700025-386031443?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.istockphoto.com/photo/wild-deer-on-the-high-plains-of-colorado-gm899371734-248171354?phrase=large+running+mule+deer&searchscope=image%2Cfilm

https://www.shutterstock.com/image-photo/white-tailed-deer-bounding-away-when-1291198885

https://www.vecteezy.com/photo/6224656-mule-deer-buck-bounding-over-prairie

https://www.mediastorehouse.com.au/ardea-wildlife-pets-environment/white-tailed-deer-buck-doe-bounding-away-tails-5295599.html

https://today.uconn.edu/2023/05/white-tailed-deer-bones-give-a-glimpse-into-connecticuts-past-and-may-help-inform-a-more-sustainable-future/

https://www.nps.gov/media/photo/gallery-item.htm?id=a4a44719-d504-4102-9dcb-0f2f3959657c&gid=FB5B2EE4-1DD8-B71B-0B202AEC100D1101

https://www.startribune.com/how-i-got-this-photo-whitetail-doe-bounds-across-woodland-trail/284798231/

https://coloradooutdoorsmag.com/2015/03/18/a-quick-guide-to-differentiate-mule-deer-from-white-tailed-deer/

https://www.jstor.org/stable/3801180

https://www.sciencedirect.com/science/article/abs/pii/S0003347219302416

https://www.jstor.org/stable/3798942

הועלה ב-פברואר 5, 2024 10:26 אחה"צ על ידי milewski milewski | 0 תגובות | הוספת תגובה

פברואר 2, 2024

Annotated photos of impalas and other bovids mislabelled as impalas on the Web

There are tens of thousands of photos labelled as impalas (Aepyceros) on the Web.

I spent today trawling through them, with two search-images.

Firstly, I sought photos particularly illustrative of various features of adaptive colouration.

Secondly, I sought the valuable photos among those of other bovids mislabelled as impalas or in other ways - of which there are thousands in their own right. These photos have been effectively 'buried' in the electronic record, but here I bring some of them back out into the light.

The following shows the VERTICALLY-PILOERECTED CAUDAL FLAG in Aepyceros melampus. The shape formed by the white hairs of the tail is similar to that of a butcher's cleaver. Unlike other ruminants, A. melampus possesses not a tassel but instead a jointed feather-tassel. The joint defines the right-angle distally, and the metaphorical blade of the cleaver is formed by piloerection perpendicular to the lateral plane:
https://www.dreamstime.com/impala-aepyceros-melampus-tarangire-national-park-tanzania-image301986232

The following shows how completely the jointed feather-tassel of A. melampus can remain hidden (by a lack of piloerection), even when the tail is untucked:
https://www.dreamstime.com/young-impala-fawn-standing-its-head-turned-toward-camera-kruger-national-park-south-africa-aepyceros-melampus-image150292156

The following shows the PENICILLATE CAUDAL FLAG in Aepyceros melampus. The distal joint in the jointed feather-tassel is open, without any other piloerection. In this case, the behaviour being flagged is micturition in adult males:
https://www.dreamstime.com/stock-photo-male-impala-side-kruger-national-park-south-africa-image77200245
https://www.dreamstime.com/stock-photo-male-impala-side-kruger-national-park-south-africa-image77199044

The following show the PEDAL FLAG of Aepyceros melampus particularly clearly. A main point to note is that, although impalas have distinct, complex, and subtle colouration, it is the pallor on the pasterns that advertise the figures:
https://www.dreamstime.com/impala-aepyceros-melampus-mother-young-masai-mara-park-kenya-image196850640
https://www.dreamstime.com/male-common-impala-stands-sunny-riverbank-image274387907

https://www.dreamstime.com/stock-photo-male-impala-rear-view-oxpecker-its-back-kruger-park-image81883072

https://www.dreamstime.com/royalty-free-stock-images-impala-ram-image21409539

https://www.dreamstime.com/royalty-free-stock-photos-young-impala-image24382208

https://www.dreamstime.com/impala-antelopes-waterhole-kruger-national-park-aepyceros-melampus-south-africa-image288451164

הועלה ב-פברואר 2, 2024 01:48 אחה"צ על ידי milewski milewski | 45 תגובות | הוספת תגובה

ינואר 31, 2024

An index to my Posts about impalas (Aepyceros)

https://www.inaturalist.org/journal/milewski/89312-annotated-photos-of-impalas-and-other-bovids-mislabelled-as-impalas-on-the-web#

Ecological niche/overall nature:

https://www.inaturalist.org/journal/milewski/50236-what-makes-the-impala-aepyceros-melampus-tick-some-initial-thoughts#

https://www.inaturalist.org/journal/milewski/89824-can-precociality-in-the-colouration-of-impalas-aepyceros-be-explained-by-their-confusing-nature-as-sedentary-plains-game-part-1#

Adaptive colouration:

https://www.inaturalist.org/posts/89191-bleezes-flags-and-semets-in-the-adaptive-colouration-of-impalas-aepyceros-part-1#

https://www.inaturalist.org/posts/89191-bleezes-flags-and-semets-in-the-adaptive-colouration-of-impalas-aepyceros-part-2#

https://www.inaturalist.org/posts/49665-the-peculiarly-complex-tail-of-the-impala-aepyceros-melampus-has-several-caudal-flags-but-no-ischial-flag#

https://www.inaturalist.org/journal/milewski/48831-why-does-the-colouration-of-the-gerenuk-litocranius-walleri-resemble-that-of-the-common-impala-aepyceros-melampus#

https://www.inaturalist.org/journal/milewski/49126-detailed-similarities-and-differences-in-the-colouration-of-gerenuk-litocranius-walleri-and-common-impala-aepyceros-melampus#

https://www.inaturalist.org/journal/milewski/89824-can-precociality-in-the-colouration-of-impalas-aepyceros-be-explained-by-their-confusing-nature-as-sedentary-plains-game-part-1#

https://www.inaturalist.org/journal/milewski/89824-can-precociality-in-the-colouration-of-impalas-aepyceros-be-explained-by-their-confusing-nature-as-sedentary-plains-game-part-2#

Locomotion and posture:

https://www.inaturalist.org/posts/49366-locomotory-and-postural-peculiarities-of-the-impala-part-1#

https://www.inaturalist.org/journal/milewski/67632-locomotory-and-postural-peculiarities-of-the-impala-part-2#

https://www.inaturalist.org/journal/milewski/67772-recent-confirmation-of-the-ability-of-the-african-savanna-buffalo-to-swim#

https://www.inaturalist.org/posts/67772-recent-confirmation-of-the-ability-of-the-african-savanna-buffalo-to-swim#activity_comment_d0627c85-085a-4fb1-b331-08b3fd21657f

Larynx:

https://www.inaturalist.org/posts/50157-the-peculiar-ordinariness-of-the-larynx-of-the-impala#

Comparison with springbok:

https://www.inaturalist.org/journal/milewski/51386-similarities-and-differences-impala-aepyceros-vs-springbok-antidorcas#

הועלה ב-ינואר 31, 2024 10:46 לפנה"צ על ידי milewski milewski | 0 תגובות | הוספת תגובה