(CNN) — Sassy, hardy, and vicious: that's how yellow-eyed penguins are fondly described by the people who spend their days working with them.
"(They) aren't as cute and cuddly as they look," says Jason van Zanten, conservation manager at Penguin Place in the Otago Peninsula, New Zealand. "They can give you a really hard slap."
Locally called hoiho, which means "noise shouter" in Māori, the yellow-eyed penguin is the largest of the penguin species that live and breed on New Zealand's mainland.
But its population has fallen dramatically in the past 30 years due to increasing threats from predators, climate change and disease. "In the last 10 or so years, we've lost about three-quarters of the population," says van Zanten.
Now, conservationists are rallying to save the species. Penguin Place -- where van Zanten works -- provides a place for hoiho to rest and recuperate while nearby, The Wildlife Hospital, Dunedin treats those with serious injury and disease.
These penguin havens are racing against the clock to save the rapidly declining population -- and give the "noise shouters" a fighting chance at survival.
The yellow-eyed penguin -- known as hoiho which means "noise shouter" in Māori -- is the largest of the penguin species that live on New Zealand's mainland. But in recent decades, hoiho numbers have plummeted. Now, conservationists are racing to save these rare birds from extinction.
Penguins in rehab
While Penguin Place is a refuge for all sick and starving birds, including other penguin species, hoiho make up the majority of patients passing through, says van Zanten.
The center was founded in 1985 when local farmer Howard McGrouther fenced off around 150 acres of his land to create a reserve for the eight breeding pairs of yellow-eyed penguins that nested on his property.
McGrouther "set up the bones of the rehabilitation center," and also started replanting native trees that were previously cleared for agriculture, says van Zanten, who began working at the center as a laborer, cutting grass and doing maintenance, and now oversees operations. The center was funded entirely by tourism until the Covid-19 pandemic, when it had to close to the public and was granted government funding through the department of conservation, says van Zanten.
Starvation is a big problem for hoiho, with around 80% of the penguins arriving at the center underweight, says van Zanten. Commercial fishing -- which has resulted in some penguins ending up as bycatch -- has reduced the availability of the small fish and squid the penguins feed on, and fluctuating sea temperatures due to climate change have altered the distribution of their prey.
"They do like it to be a little bit cooler, and with our rising temperatures, they are getting stressed out a lot more and overheating," says van Zanten.
A mystery disease
Aside from starvation, many hoiho arrive at the Penguin Place with disease and injury -- and that's where The Wildlife Hospital, Dunedin, which specializes in native species, steps in.
On land, hoiho are hunted by mammals including dogs and stoats, which can leave them or their chicks seriously wounded, while in the water, sharks and barracouta, a predatory fish with razor sharp teeth, often inflict "horrific injuries," says Lisa Argilla, a senior wildlife vet and director of The Wildlife Hospital, Dunedin.
Hoiho typically stay at Penguin Place for around two weeks, to rest, recover and fatten up before returning to the wild.
Ben Foley / CNN
Hoiho also suffer from various diseases, including avian malaria and dermatitis, which the hospital can treat with antibiotics. Additionally, avian diphtheria has ravaged the hoiho population in the past 20 years: it causes lesions, similar to ulcers, in the bird's mouth and makes it difficult for them to eat, ultimately leading to starvation.
And now there's another new, unknown disease affecting hoiho chicks. Tentatively referred to as "red lung", the disease causes respiratory problems, according to Kate McInnes, a threatened species veterinarian at the department of conservation in New Zealand.
Cases started appearing five years ago but "there's been a significant increase over the past two (years)" says McInnes. She adds that the disease doesn't appear to be infectious, but researchers are still trying to determine the cause.
If chicks arrive at the hospital already sick with the mystery illness, Argilla says they can't be saved. But Argilla and her team have found a solution: hand-rearing chicks at the hospital.
"If we get them at a certain age, when they're very young, we can actually prevent them from getting this disease," she says. The chicks are taken from their nests shortly after hatching, and are reunited with their parents in the wild after 10 to 14 days.
For sick and injured birds, The Wildlife Hospital sends them to Penguin Place after treatment, where they recover before being released back to the wild, says Argilla. "It's exciting for us to know that what we are doing is actually making a difference."
A chance to bounce back?
Back at Penguin Place, the hoiho are kept in small enclosures with rocks, wooden blocks and shelters. They are put on an intensive feeding program to fatten them up before release, and fed fish twice a day.
Most birds stay in the center for around two weeks before they are released into the reserve where they can mate and nest, says van Zanten, adding "the more they're in the wild, the better for them."
As the world's only solitary species of penguin, hoiho are antisocial and don't like to nest within sight of their neighbors -- sometimes even abandoning their eggs if they spot another penguin, says van Zanten. To make them feel more secure, Penguin Place has scattered little A-frame wooden houses across the reserve, hidden beneath the shade of trees and bushes near the beach.
Penguin Place offers tours of the reserve to visitors through camouflaged, hand-dug tunnels, so that tourists can spot the hoiho in their natural habitat without disturbing them.
Ben Foley / CNN
While there's always a risk when removing animals from the wild, McInnes says a hands-on approach to conservation is necessary: "If we don't interfere, a large number of those chicks will die." She anticipates an increase in breeding pairs returning to the beach over the next year or two, as a result of the interventions.
And van Zanten is optimistic that the species can bounce back. Penguin Place boasts an extremely high success rate: more than 95% of the 200 to 300 birds that come to the center every year are released back to the wild, he says. Last year the center achieved a personal best, with 99% of birds released, giving hope for this critically endangered bird.
"The work we are doing is absolutely critical for these (penguins), and their survival here on the mainland," says van Zanten.