Animal Nerd

Koala, Phascolarctos cinereus. July 2010, Queensland, Australia.
Koalas smell like a craft store and are not as soft as they look, but I still want one. The mother koala in the top picture chomped the one behind her just after the picture was taken, because it was trying to walk over her on its way along the branch.

According to wikipedia, the brain in the ancestors of the modern koala once filled the whole cranial cavity, but has become drastically reduced in the present species, a degeneration scientists suspect is an adaptation to a diet low in energy. One of the smallest in marsupials with no more than 0.2% of its body weight, about 40% of the cranial cavity is filled with cerebrospinal fluid, while the brain's two cerebral hemispheres are like "a pair of shrivelled walnut halves on top of the brain stem, in contact neither with each other nor the bones of the skull. It is the only animal on Earth with such a strangely reduced brain."