EPOW - Ecology Picture of the Week

Each week a different image of our fascinating environment is featured, along with a brief explanation written by a professional ecologist.

2-8 June 2008

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The Devil with the Tiny Brain

Skull of Tasmanian Devil (Sarcophilus harrisi)
Family Dasyuridae, Order Marsupalia
Tasmania, Australia

Credit & Copyright: Dr. Bruce G. Marcot

Explanation:  What seems odd about the proportions of this skull?  This is a casting of an actual skull of a Tasmanian devil, found in the island state of Tasmania, Australia.  

Look at the relative size of the brain case, which is on the left in the main photo above.  It is ... tiny!  

Compared to its body size, the Tasmanian devil has a remarkably diminutive brain.  But devils have a relatively complex social structure, with clear hierarchies and dominant individuals who get to feed and breed first.  This combination of big body and tiny brain rather belies an otherwise orderly pattern that suggests that evolution favors larger (and heavier) brains with larger (and heavier) bodies.  

The devil skull, though, is clearly built for ... biting, with a bite strength, pound for pound, that is sometimes said to rival that of hyenas.  Devils may even have the most powerful bite of all mammalian carnivores anywhere!  

In part, the shape of the skull supports massively powerful jaw muscles that can crush bones.  Tasmanian devils are the largest living carnivorous marsupial.  I once witnessed a group of devils on Tasmania devouring a dead pademelon (a small kangaroo-like marsupial), all the while snarling and jockeying for position in their feeding hierarchy, crunching bones in the dark.  

 

 

Those aren't huge eye sockets; they are insertion points for the massively powerful lower jaw.


 

Tasmanian devils have large, strong canine teeth and molars with strong sharp cusps for shearing and crushing.  The fourth molar has a small ridge at right angles to the other molars, probably for additional shearing and crushing action.


 

Notice also the prominent sagittal crest on the top of the brain case.


Unfortunately, Tasmanian devils have recently been hit hard by what is called the "Devil Facial Tumour Disease" pretty much throughout their sole current distribution in Tasmania.  

   

Next week's picture:  Harpoon Fishing in the Congo


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