Our two populations of hoiho
There are two populations of hoiho in New Zealand. Movement of hoiho between the two is rare.
Over the past 20 years, the northern population has declined by 65%, while the status of the southern population is not well documented.
The northern population includes hoiho on the South Island (Banks Peninsula to the southern Catlins), Stewart Island/Rakiura and adjacent islands.
The southern population are those on the Subantarctic Auckland Islands and Campbell Island.
Decline of the northern population
The size of the hoiho population is measured in breeding pairs. This is determined by searching for nests during the breeding season.
In 1999 there were about 741 breeding pairs in the northern population. The 2019 estimate was 265 breeding pairs, a 65% decline in 20 years.
The decline was due to a series of poor breeding seasons caused by lack of food, disease and predators.
Unfortunately a 2020 survey on Rakiura showed a similar pattern of decline (c. 71%) from 154 pairs in 2008/09 to 44 pairs in 2020/21. The total 2020 estimate for breeding pairs in the northern population was 233.
Is the hoiho southern population stable?
In 2017 an estimate of 570 breeding pairs was made for the southern population of hoiho on the Auckland Islands. This was consistent with an estimate made in 1989 of a minimum of 520 breeding pairs.
There are no recent estimates for the Campbell Island population. The last estimate was in 1992 of about 400 breeding pairs.
Only a small amount of research and monitoring work has been carried out on Campbell and the Auckland Islands. How far the penguins are from the mainland limits our ability to do more.
In 2020, a new recovery strategy and five-year action plan was released by DOC and our partners Te Rūnanga o Ngāi Tahu, the Yellow-eyed Penguin Trust/Te Tautiaki Hoiho, and Fisheries New Zealand/Tini a Tangaroa.
We also work with The Yellow-eyed Penguin Trust, the Wildlife Hospital Dunedin, Penguin Rescue, Penguin Place and other groups, to protect hoiho and restore habitat across most of the South Island range.
This work includes:
- predator control
- monitoring their nests
- disease and injury treatment
- starvation interventions
- planting of native vegetation to restore hoiho habitat.
What challenges do hoiho face?
During the breeding season hoiho face a variety of threats. They have to deal with disease that affects both chicks and adults, mammalian predators attacking small chicks and the effects of starvation on both adults and chicks.
Hoiho also face predation (for example, by barracouta), climate-driven changes in food supply and dog attacks while ashore for the moult. Another threat to hoiho is incidental capture in set nets.
We undertake research into what and how hoiho are eating, what’s causing disease and how to treat it, and their behaviours at-sea. We are also extending protection and management to Rakiura and Whenua Hou.
This has helped us understand several reasons hoiho have declined or been unable to grow their population, including:
- Human disturbance
- Introduced and natural predators
- Habitat quality
- The health of our seas and fishing
- Vaccine development
People who visit hoiho habitats and disturb them threaten nesting and moulting birds.
When people enter nesting areas or linger on beaches where hoiho come ashore it can disturb and stress nesting penguins. This can lead to adults delaying their return to their nest and their chicks.
Disturbances like these can mean adult penguins cannot readily feed their chicks, affecting weight gain. In years of poor food supply, a missed meal for a chick may be life or death. This impact can reduce survival rates and limit the number of penguins who will breed in the following season.
Each autumn, the penguins also replace all their feathers in a process called the moult. During this time penguins must sit ashore for 25 days to grow new feathers and can't go to sea to feed. The moult is a very dangerous time for penguins because if they’re disturbed, this lengthens the process which can lead to starvation.
Disturbance during the moult can lead to hoiho damaging new growing feathers which can increase the risk of hypothermia when the birds return to sea. If hoiho moult in areas where they can be disturbed, rangers move them to safer habitats.
Hoiho are at risk from introduced predators, dogs and cats as well as their natural predators. In the past, hoiho have thrived despite their natural predators in the sea. But introduced predators, brought to New Zealand by humans, have added a lot of pressure to their numbers.
On the mainland, introduced predators such as stoats and ferrets are a major risk to hoiho chicks. They have been known to completely wipe out a breeding area in a single season. Cats also predate hoiho chicks.
Dogs threaten hoiho as they can kill chicks to adult penguins. From February to April, hoiho and other penguins remain ashore to moult. They may do so on beaches where penguins are not normally present. This makes them very vulnerable to dogs, making this a crucial time for owners to keep their dogs under control.
On Auckland Island and in some other areas, feral pigs have been recorded eating hoiho. DOC is investigating how to remove pigs from the island to protect them and other native species.
Hoiho’s natural predators include sharks, seals and sea lions. Penguins are sometimes seen with bite injuries to the feet, flippers and body which, if left untreated, can be fatal. Some of these injuries are caused by sharks, and others may be because of encounters with barracouta.
Hoiho need coastal forest and shrubland that’s free from predators and people, to rest, socialise, nest and moult.
Much of the coastal forest and shrubland on the east coast of the South Island was burnt or cleared for farming. This left only small areas of coastal vegetation available to hoiho.
Since the 1980s, DOC and community groups have worked to provide better habitats for hoiho. This ongoing work has included:
- protecting coastal sites and replanting them with native shrub
- providing resting spaces, social areas, nesting boxes and safe places to moult
- control of introduced predators to protect hoiho and their nests
- managing visitors so they’re not disturbed.
Hoiho rely on thriving marine environments for their food. They need suitable fish that will nourish their young and provide vital nutrition for their moult. Less suitable foods at key times can lead to chick starvation or adult deaths during the moult.
We have undertaken considerable research on where and how hoiho forage at sea. Read a summary of this work: Hoiho/yellow-eyed penguin population and tracking report.
A suitable diet for hoiho comprises key species of fish and squid. Red cod, opal fish and sprat have all been shown to be important foods for them in studies carried out during the 1980s. However, recently they have been found to be feeding on blue cod instead of red cod. Blue cod aren’t as nutritious for hoiho, but as there is less red cod in our seas, they have no choice. Warmer sea temperatures off the east coast of the South Island combined with fishing pressure have likely contributed to the decline of red cod.
Hoiho feed mostly on the sea floor and can dive to depths of up to 160 m. They are sometimes caught in commercial set-nets. Trawlers that disturb the seafloor may also cause changes to the environment and the species that live there. This can make it harder for hoiho to find and catch the fish they need.
Disease is a major threat to chick and adult survival. Hoiho are at most risk of two disease types: bacterial infection and blood parasites.
A bacterial infection called diphtheritic stomatitis, or avian diphtheria, can affect the mouths of hoiho chicks. It prevents them from feeding and drinking and lead to more illnesses and death.
Two blood parasites also affect hoiho called leucocytozoon and avian malaria. Both threaten the lives of hoiho chicks. Spread by mosquitoes, avian malaria now threatens adults too. This is because wetter and warmer weather has increased the numbers of mosquitoes.
There have also been times when many healthy hoiho have died at once because of unknown causes. It’s assumed a poisonous substance in the seas may have caused these extreme events. But post-mortems and lab tests have not yet determined this.
Teams of researchers, based at Otago, Massey and Northumbria Universities and supported by DOC, have been working to understand and develop a vaccine for diphtheria type infections that have been killing off hoiho.
You can help
Keep our penguins safe
- Leave penguins alone. Usually scruffy birds are simply moulting.
- Put your dog on a leash around penguin areas.
- Keep your dog away from nests, and warn others nearby of the location.
- Donate your time or money to help penguin protection groups, such as the Yellow-eyed Penguin Trust and Forest & Bird.
If you find a dead or injured penguin
If you find a dead penguin, leave it alone. Community groups regularly count dead seabirds and will remove them from beaches.
If a sick penguin is at risk from attack by dogs or other predators, place it under vegetation in the rear-dune well away from people. Or you can take it to a local bird rescue centre.
Do not give emaciated penguins food. The rehabilitation of seabirds requires specialist knowledge and training.
If a penguin is clearly injured or in immediate danger, contact the emergency hotline 0800 DOC HOT (0800 362 468). Try and give the exact location and take photos to help us make an assessment.