What a really small-brained mammal (Echymipera rufescens) looks like
The following photos show the long-nosed echymipera (Echymipera rufescens, https://en.wikipedia.org/wiki/Long-nosed_echymipera) of Cape York Peninsula and New Guinea. This is among the smallest-brained of all land mammals for its body size.
If this species is dexterous enough to hold food in its fore feet while eating, then I find that remarkable.
The greater glider (Petauroides volans, https://www.inaturalist.org/taxa/42783-Petauroides-volans) has similar body mass to E. rufescens, i.e. 1700 g. The greater glider has brain volume of 4.7 whereas this bandicoot has brain volume of 3.7.
The greater glider is surprisingly decephalised for a member of the possum group of diprotodontians (being far smaller-brained even than the bilby Macrotis lagotis). This fact can be understood in terms of the diet of this glider, which is almost exclusively the leaves of eucalypts.
However, the long-nosed echymipera (which I assume to be omnivorous) really is so decephalised that it represents an extreme - not only for marsupials, but also for land mammals more widely.
I would be interested to know whether either the long-nosed echymipera or the greater glider is capable of manipulating food. My suspicion is that the long-nosed echymipera does indeed hold food while eating, which would mean that it is anomalous in dexterity relative to encephalisation among mammals generally.
https://c1.staticflickr.com/5/4415/36539569616_a5a03e2e1b_b.jpg
https://static.inaturalist.org/photos/216104/large.jpg?1444464116
https://static.inaturalist.org/photos/254016/original.jpg?1444661362
Echymipera rufescens body mass 1.7 kg, brain mass 3.73 g
Isoodon macrourus body mass 1.6 kg, brain mass 4.42 g
Isoodon obesulus body mass 0.775 kg, brain mass 3.89 g
Macrotis lagotis body mass 1.8 kg, brain mass 6.57 g
Macrotis leucura body mass 0.356 kg, brain mass 4.3 g
Perameles bougainvillei body mass 0.226 kg, brain mass 3.21 g
Perameles gunnii body mass 0.75 kg, brain mass 4.5 g
Perameles nasuta body mass 0.96 kg, brain mass 4.96 g
Other marsupials of body mass about 1.8 kg:
Bettongia gaimardi body mass 1.66 kg, brain mass 11.7 g
Didelphis marsupialis body mass 1.62 kg, brain mass 6.35 g
Didelphis virginiana body mass 1.9 kg, brain mass 6.72 g
Lagostrophus fasciatus body mass 1.75 kg, brain mass 7.0 g
Petauroides volans body mass 1.7 kg, brain mass 4.69 g
THE VARIOUS CLADES CONTAINING THE LEAST BRAINY MAMMALS ON EARTH
Species of mammals with encephalisation quotients <0.5 occur in a surprisingly wide range of
orders/superorders, viz.
- Peramelemorphia (bandicoots),
- Diprotodontia,
- Dasyuromorphia,
- Ameridelphia,
- Xenarthra (excluding sloths and myrmecophages),
- Laurasitheria, and
- Euarchontoglires.
Specific examples include
- Macropus giganteus 0.47 (https://www.inaturalist.org/taxa/42888-Macropus-giganteus)
- Didelphis marsupialis 0.46 and Monodelphis (https://www.inaturalist.org/observations?place_id=any&subview=map&taxon_id=42562&view=species)
- Suncus murinus 0.48 (https://www.inaturalist.org/taxa/46531-Suncus-murinus)
- Afrosoricida: Setifer setosus 0.45 (https://www.inaturalist.org/taxa/42477-Setifer-setosus), Oryzorictes hova (https://www.inaturalist.org/taxa/42471-Oryzorictes-hova), and Condylura cristata (https://www.inaturalist.org/taxa/47056-Condylura-cristata)
- Galeopterus variegatus (https://www.inaturalist.org/taxa/74351-Galeopterus-variegatus)
- Oryctolagus cuniculus (perhaps only domestic breeds, https://www.perplexity.ai/search/is-there-a-difference-in-eq-be-IhjDZU6uTV.b97ZxxtXf3Q).
The only ungulates qualifying for encephalisation quotients <0.5 are Hippopotamus amphibius, the largest-bodied bovine (possibly not qualifying if adult females are considered), and Sus scrofa domestica (https://www.perplexity.ai/search/eq-of-domestic-pig-u972MshWSeqHJ9LFX5_ljw).
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