Threats, disease and predators
Several species, including New Zealand sea lions, fur seals, sharks and barracoutas, are known to predate or injure yellow-eyed penguins.
Yellow-eyed penguins are adapted to life ashore in the cool coastal forests and shrublands of New Zealand. But in these once extensive habitats, they became casualties to the needs of newly arrived humans. Not only did Maori hunt yellow-eyed penguins as food, but also Maori and European fires destroyed vast tracts of these forests. Most of the remaining forests were cleared for farming or urban development, and yellow-eyed penguin numbers collapsed alarmingly. Today, the surviving fragments of forest and scrub are insufficient to support a vibrant, flourishing yellow-eyed penguin population.
Marooned in tiny patches of failing bush they found themselves challenged by a number of unfamiliar predators introduced by humans. Dogs, cats, possums and large mustelids (stoats and ferrets) began to prey on yellow-eyed penguin adults, eggs and young. Sheep and cattle trampled nests and browsed on the vegetation, which sheltered yellow-eyed penguins from the sun. Yellow-eyed penguins could not cope with these threats.
Fat and heavily feathered, the yellow-eyed penguin is perfectly insulated for foraging in the depths of the cold southern ocean. But ashore, in this warm temperate climate, the heavy insulation becomes a liability. The birds cannot remove their ‘wetsuits’, but must find shady, moist undergrowth to avoid lethal rises in body temperature. Shade also helps yellow-eyed penguins to regulate the incubating temperature of their eggs.
At sea, yellow-eyed penguins face not only their natural predators but also fishing set-nets, which drown them. There are indications that global warming may be impacting on oceanic processes and altering the food webs on which yellow-eyed penguins depend. These are longer-term problems to work on. Occasionally, yellow-eyed penguin populations suffer terribly from epidemics of diseases that we can do little to prevent, such as Corynebacterium.
These dangers seem impossible to overcome, but many are manageable if resources are available. The Yellow-eyed Penguin Trust assists the penguins by alleviating the pressures we humans have imposed on them. Once free of these threats, yellow-eyed penguins are capable of doing the rest.This is a rewarding partnership, which succeeds if we do our bit.