Predators, Problems and Threats
During the yellow-eyed penguin breeding cycle or during the moult, human disturbance (which could simply be walking on a beach where Hoiho are coming ashore to feed its chicks) may push a bird over the threshold from survival to starvation leading to:
- Nest abandonment
- Reduced fledgling weights – which mean the chicks have lower chances to survive their first year at sea
- A reduced number of chicks
- A reduction in the breeding population·
Research shows that where there is extensive human interaction on a beach where adult yellow-eyed penguins need to cross to get to their nests and chicks, chick survival can be as low as 0.6. Whereas, at nearby colonies that aren’t accessible there is a survival rate of 1.7.
Researching the problem
Finding out just how stressed a Yellow-eyed Penguin can get, Otago University PhD student Ursula Ellenberg and colleagues measured penguins’ heart rate using an egg-shaped micro-recorder that was added to the other eggs in the nest.
As the penguin settles on the eggs to incubate them, the micro-recorder picked up their heartbeat transmitting it to the researchers’ hide. The researchers then conducted a series of disturbance experiments, in which a person walked slowly and steadily up to a nest, stopped a short distance away, waited for a minute and then walked away. Ellenberg and her colleagues found that female penguins took longer to recover from the stress of a visit by a human (i.e. it took longer for their heart rate to return to normal) than males.
Read the press release about yellow-eyed penguin fatalities reported to the Department of Conservation and the Otago Daily Times article about a yellow-eyed penguin being killed by a dog just after it had been released from the Penguin Place hospital.
3. Mustelids -weasels ferrets and stoats
Stoats are now considered “public enemy number one” for New Zealand birds. They have been known to take a yellow-eyed penguin egg from underneath an adult.
It is estimated that there are 220 cats per square kilometre in New Zealand. For an insight to the wildlife and cat problem read the Otago Daily Times article about how ‘Dumped cats threaten precious wildlife’. For more information read ‘When Pets Go Bad’ from the Department of Conservation and the Yellow-eyed Penguin Trust.
5. Sea predators
Yellow-eyed penguin’s natural predators are sea lions, sharks and barracouta. Leopard seals, usually residents of the Antarctic region, are specialist penguin predators while sea lions only occasionally dine on penguins. Sharks and barracouta are the main marine predators.
Sharks have been known to kill an unknown number of mainly young penguins but they also inflict injuries on others. Barracouta who bite at the feet of the penguins, cause injuries that in themselves are not fatal but then often become infected. When birds are injured or under-nourished they also become more susceptible to disease.
Barracouta very regularly injure penguins with cuts to the feet or body. The wounds inflicted can be treated in rehab but if the foot bone gets infected then the bird will no longer be able to forage and will die.
8. Sea lions
New Zealand sea lions are only found in New Zealand. Also known as Hooker’s sea lions, they are one of the rarest species of sea lion in the world and are now critically endangered.
Te Rere Reserve in the Catlins: In the early 1980s Southland Forest & Bird got agreement of the farmer to fence off the area where the penguins nested, and in 1988 Forest & Bird bought the land and established the Te Rere penguin reserve. Restoration on the area started a year after the farmer had bulldozed the land.
Numbers had built up to 100 adult birds when in February 1995 a fire swept through the reserve, killing more than 60 – a devastating loss to the breeding colony, and a serious blow for the species.