The yellow-eyed penguin may be the rarest penguin in the world. The coastal forests of their habitat, particularly of mainland New Zealand, have been destroyed to make way for development and agriculture. Introduced sheep and cattle pose a threat as they can trample on penguin nests and overgraze the area, destroying further habitat (2). In 1986 and 1990 there were two major population crashes, the causes of which remain a mystery (6). The other major threat to the yellow-eyed penguin comes from introduced mammalian predators such as ferrets, cats, rats and dogs; juvenile penguins or adults during their moult phase are extremely vulnerable to predation and numbers have been decimated over the years (2).