Junveniles have a grey iris and grey head band, both turning yellow when they mature
The yellow-eyed penguin/hōiho (Megadyptes antipodes) is named because of its yellow iris and distinctive yellow head band.
Adults are slate grey in colour, with a white belly and flesh-coloured feet that become bright pink during exercise.
Hōiho chicks are covered in thick, brown fluffy down, which begins to shed once their juvenile plumage develops at around 70 days.
Hōiho chicks fledge between 98 to 120 days. Their juvenile plumage is different to adults and can be distinguished by their grey iris, grey head band and dull head plumage. Adults (2 to 25 years) have a yellow iris and yellow band on their crown. Once a juvenile bird undergoes its first moult in the year after fledging, it acquires the yellow band and eye colouring of an adult.
The Māori name hōiho means 'noise shouter'. This refers to their shrill call, often heard when they encounter their mate or others at their breeding site.
Their diet is made of small to medium sized fish such as sprat, red cod, blue cod, ahuru, opalfish, silversides and squid. Hōiho are very selective and dive to the sea floor to gather their prey1.
The average lifespan is 8 years, but several birds have reached over 25 years of age2.
Adults reach up to 65 cm in height and weigh around 5 to 5.5 kg. Before moulting adults and juveniles can weigh up to 9 kg.
During the moult hōiho must sit ashore for 25 days and grow new feathers, and they are unable to go to sea.
Unlike other penguin species, hōiho are not typically colonial, and their breeding areas cannot be called 'colonies'. Hōiho seek out private nesting areas with a solid back and a roof for egg laying. Two eggs are laid in a shallow bowl lined with delicately gathered sticks, ferns and fronds3.
Hōiho are philopatric, which means they usually come back to the area they were born to breed. Juveniles may wander in their first year, with female hōiho beginning breeding between 2-3 years, and male hōiho starting breeding between 3-6 years of age2. Adults stay near their breeding area for life, and do not migrate elsewhere during the non-breeding part of the year2.
Yellow-eyed penguins are wild, and do not become habituated to human disturbance. As a result they are not suitable for holding in permanent captivity.
Threats include habitat destruction, predation, disease and human interference
The yellow-eyed penguin is equally dependant on marine and land habitats, which include forest and coastal scrubland. A great deal of community effort has been put into providing nesting sites and shelter on grazed pasturelands on the Otago Peninsula and North Otago.
These habitats provide nesting opportunities, as well as social areas and loafing space, and a space to take refuge during the 25-day moult each year.
The yellow-eyed penguin's marine habitat is equally important because it provides food, and allows for dispersal and movement between land habitats.
Population and range
In 2000, the total number of individual penguins was estimated to range between 6,000 to 7,000 mature individuals, although the number of individuals varies widely4. The IUCN rank hōiho as an Endangered Species. Within New Zealand hōiho are considered threatened and nationally vulnerable.
The key figure used to assess population size is the number of breeding pairs.
Monitoring, research, and intensive management are carried out by community groups and DOC on Banks Peninsula, in North Otago, Otago Peninsula, the Catlins, Stewart Island/Rakiura and Codfish Island/Whenua Hou. Most sites have been monitored annually since the early to mid 1980s.
Due to the isolation of New Zealand's Subantarctic Islands, only a small amount of research and monitoring has been done on Campbell Island and the Auckland Islands. Research trips in 1987, 1992, 2008-2009, and more recently have yielded snapshot information about the health and status of these Subantarctic populations.
In the 1980s, research and monitoring on the Otago Peninsula indicated that the number of breeding pairs had declined significantly, leading to fears for the future of the mainland population. In addition, predators were killing up to 60% of chicks at some sites3.
A steep decline in nest numbers throughout the 1980s, followed by a mass mortality event in January 1990 reduced the total number of nests to as low as 140 pairs on the entire Otago coast in the following season. Since this time nest numbers have fluctuated between 400 to 600 pairs.
In the current 2015/16 season, there are less than 200 breeding pairs on the Otago coast. The steep decline in nest numbers is the cumulative effect of another unidentified mass mortality in January 2013, widespread starvation in 2014, and an increase in predation by barracouta in early 2015.
Having a half and half existence - marine and land - hōiho need access to a private, scrub- or bush-covered area to breed. Areas adjacent to the coastline that have been burnt or developed for farming or other forms of land development restrict their nesting options.
Yellow-eyed penguins are solitary creatures that seek privacy. Hōiho will walk up to one kilometre inland to find nesting sites. A major focus for hōiho conservation has been on replanting coastal sites with native shrubs and plants, and by providing nesting boxes as alternative habitats.
On the mainland, stoats and ferrets are major predators of chicks, and can completely wipe out a breeding area in a single season. Cats are also known to predate hōiho chicks. Stoats and ferrets are trapped by conservation volunteers and landowners at most mainland breeding areas, and some cat control is also undertaken.
Dogs are the most significant predator of hōiho on land, killing chicks, juveniles and adult penguins. The most critical time for owners to control their dogs is during the moulting period, from February to April each year, as moulting hōiho can be found on any coastal beach.
Natural predators include barracouta, sharks, seals and sea lions. Injuries from barracouta are the most common, with bites to the feet, legs and abdomen eventually becoming fatal if left untreated.
Disease is a major threat to chick and adult survival.
Two diseases affect survival of chicks: avian diphtheria (also known as diphtheritic stomatitis), a bacterial infection of the mouth; and Leucocytozoon, a protazoal parasite of the blood and organs.
Lesions are visible on the sides of the mouth and under the tongue
DOC's Kate McInnes removing avian diptheria lesions from the mouth of a young chick
In 2004, up to around 90% of the mainland and Stewart Island chicks were infected with avian diphtheria. More than 50% of chicks died from this disease. Outbreaks of avian diphtheria tend to occur every second season, and research into prevention is ongoing.
A new disease, Leucocytozoonosis, was identified during the 2005 season that caused mortality of chicks on Stewart Island. Yellow-eyed penguin chicks on the Auckland Islands were also found to be infected with Leucocytozoon during disease screening in 2008.
There have been three unidentified mass mortality events that have killed large numbers of breeding adults and juvenile birds in 1990, 1996 and 2013. It is assumed that a marine biotoxin was responsible for these extreme events, but post mortems and lab tests did not pinpoint the toxin involved.
In some readily accessible sites the popularity of unregulated ecotourism is having a detrimental effect on chick survival rates and recruitment of new breeders. Adults are delayed from landing on the beach and reaching their nest site because of tourists crowding to take photographs and approaching hōiho too closely. Without being able to fly away, hōiho have to calculate the fight or flight response - to run back to sea, or to stand frozen. Research indicates that chicks that continuously miss meals during the breeding season fledge significantly lighter than chicks from undisturbed sites5. In years of poor food supply, a missed meal for a chick may be life or death.
Species conservation plan
A species conservation plan was established in 1985 before DOC was formed. This was in response to the population instability in the South Island during the 1980s.
The plan outlined a number of objectives, particularly the immediate, urgent requirement to stabilise hōiho numbers at or above present levels. Different plans were written in 1989, 1991 and 1997.
Hōiho recovery plan
A Hōiho (Megadyptes antipodes) recovery plan 2000-2025 (PDF, 343K) was approved in 2000, and carries on from the species conservation plan before it.
The Recovery Plan consists of nine key objectives that will promote the recovery of hōiho populations throughout their range. It also outlines different management options, and a work plan. The Long-term vision of the recovery plan is: 'Hōiho populations have increased and the community is actively involved in their conservation.'
A stocktake of the progress against the objectives of the current Hōiho Recovery Plan is underway, which will inform any new conservation management plans for hōiho.
Monitoring and research
During 2011, DOC scientists attached dataloggers to penguins at Stewart Island/Rakiura to record the depth, length and shape of their dives during one feeding trip in the sea nearby.
Penguin diving behaviour and ecosystem monitoring factsheet (PDF, 10,220K)
Yellow-eyed Penguin Trust (YEPT) and DOC, with other key groups, have been involved with penguin monitoring.
1 van Heezik Y, 1990a. Seasonal, geographical, and age-related variations in the diet of the yellow-eyed penguin (Megadyptes antipodes). New Zealand Journal of Zoology 17 (2): 201-212.
2 Stein AM, 2012. Lifetime reproductive success in yellow-eyed penguins: influence of life-history parameters and investigator disturbance: a thesis submitted in partial fulfillment of the requirements for the Degree of Master of Wildlife Management, Department of Zoology, University of Otago, Dunedin, New Zealand. 67p.
3 Darby JT, and Seddon PJ, 1990. Breeding biology of yellow-eyed penguins (Megadyptes antipodes). In: Penguin Biology. Edited by LS Davis and JT Darby. Academic Press, San Diego USA.
4 McKinlay B, 2001. Hoiho (Megadyptes antipodes) Recovery Plan 2000 - 2025. Threatened Species Recovery Plan 35. Department of Conservation, Wellington, New Zealand. 27p.
5 McClung M, Seddon PJ, Massaro M, and Setiawan AN, 2004. Nature-based tourism impacts on yellow-eyed penguins Megadyptes antipodes: does unregulated visitor access affect fledging weight and survival? Biological Conservation 119: 279-285.