Rio is a California sea lion who can solve IQ tests that many people have trouble passing. In fact, she is so smart that scientists at the Long Marine Lab at the University of California, Santa Cruz designed a series of tests that prove she is the first animal besides humans that can use basic logic (If A=B and B=C then A=C). Rio's display of intelligence is less surprising when you consider the fact that she is a member of one of only four groups of animals that have evolved extremely large brains (weighing more than 1.5 pounds). Along with seals and walruses, she is part of a group of fin-footed, semiaquatic marine mammals called pinnipeds. The other large-brained groups are humans, elephants and cetaceans (whales and dolphins).

Despite considerable evidence of their cerebral skills, very little is known about pinniped brains. However, a team of neuroscientists at Vanderbilt University has taken an important step toward rectifying this lack of knowledge by conducting the first comprehensive study of the California sea lion's central nervous system, concentrating on the somatosensory system, which is concerned with conscious perception of touch, pressure, pain, temperature, position and vibration.

Last year, the dramatic upsurge of juvenile California sea lion deaths due to strandings throughout central and southern California made it possible for Sawyer to obtain two juvenile sea lion brains for study. (Sea lions, like all marine mammals, are protected by the federal government under the Marine Mammal Protection Act of 1972.)

The results of their study are described in the paper "Somatosensory brain stem, thalamus and cortex of the California sea lion (Zalophus californianus)" published online in the early view of the Journal of Comparative Neurology.