The Mediterranean monk seal is one of the most endangered mammals in the world (5). The description of this species by Aristotle was the first known written description of a pinniped (a group that includes seals, sea lions and walrus) (2), and the head of a monk seal appeared on one of the first ever coins, around 500 BC (5). Adults have a brown or grey coat, which becomes paler on the undersurface (2) and males often feature a white patch on the belly (5). Old males are darker in colour and often become black, but retain the ventral white patch. Newborn infants are black and woolly with a white or yellow patch on the belly, the shape of which can sometimes be used to determine the sex of an individual (2).