This highly social and intelligent species is well adapted to a semi-aquatic life-style. California sea lions swim using their fore-flippers and are particularly agile on land as they are able to control their hind flippers independently (3). Male and female California sea lions differ significantly in appearance. Males are substantially bigger than females and have an enlarged sagittal crest, which is usually topped with white fur. The adult males are generally dark brown with a lighter belly and side colouring, whereas the females can appear more tan coloured. The pups are born with a blackish-brown coat which moults after a month and is replaced with a light brown coat. This coat is shed after four or five months and replaced with the adult coat. The California sea lions found in Mexico appear smaller than those found in California (2).