The yellow-eyed penguin (Megadyptes antipodes), known also as hoiho, is a species of penguin endemic to New Zealand. It is the sole extant species in the genus Megadyptes, from Ancient Greek μέγας (mégas), meaning "large", and δύπτης (dúptes), meaning "diver". Previously thought closely related to the little penguin (Eudyptula minor), molecular research has shown it more closely related to penguins of the genus Eudyptes. Like most penguins, it is mainly piscivorous. The species breeds along the eastern and south-eastern coastlines of the South Island of New Zealand, as well as Stewart Island, Auckland Islands, and Campbell Islands. Colonies on the Otago Peninsula are a popular tourist venue, where visitors may closely observe penguins from hides, trenches, or tunnels. On the New Zealand mainland, the species has experienced a significant decline over the past 20 years. On the Otago Peninsula, numbers have dropped by 75% since the mid-1990s and population trends indicate the possibility of regional extinction from the peninsula in the next 20 to 40 years. While the effect of rising ocean temperatures is still being studied, an infectious outbreak in the mid-2000s played a large role in the drop. Human activities at sea (fisheries, pollution) may have an equal if not greater influence on the species' downward trend.
Taxonomy The yellow-eyed penguin was first described by Jacques Bernard Hombron and Honoré Jacquinot in 1841. The yellow-eyed penguin is the sole species in the genus Megadyptes, though there have been multiple subspecies. It was previously thought closely related to the little penguin, but molecular research has shown it is more closely related to penguins of the genus Eudyptes. Mitochondrial and nuclear DNA evidence suggests it split from the ancestors of Eudyptes around 15 million years ago. In 2019 the 1.25Gb genome of the species was published as part of the Penguin Genome Consortium, aiming to understand the origins and aid conservation by helping to inform any future breeding programmes.
Subspecies
Megadyptes antipodes antipodes The hoiho or yellow-eyed penguin (M. a. antipodes) is the only extant subspecies. They were formerly most abundant in the subantarctic Auckland and Campbell Islands, and colonised Stewart Island / Rakiura and parts of the South Island following the extinction of the Waitaha penguin. There are proposals to split the yellow-eyed penguin into three further subspecies due to genetic differences. Genome sequencing of 249 penguins from across the New Zealand mainland and the subantarctic Enderby and Campbell Islands identified clear genetic divisions in each location with negligible gene flow between the populations, consistent with there being three distinct subspecies. Based on comparisons of these genomes the authors estimated that the three lineages diverged between 5,000 and 16,000 years ago, although the proposed historic co-existence of two Megadyptes subspecies in southern New Zealand remains unexplained.
Megadyptes antipodes waitaha The Waitaha penguin (M. a. waitaha) is an extinct subspecies that was present in the North Island, the South Island, Stewart Island, and Codfish Island / Whenua Hou. Last dated to AD 1347–1529. It was discovered by University of Otago and University of Adelaide scientists comparing the foot bones of 500-year-old, 100-year-old and modern specimens of penguins. According to lead researcher Sanne Boessenkool, Waitaha penguins "were around 10% smaller than the yellow-eyed penguin. The two species are very closely related, but we can't say if they had a yellow crown". The penguin was named after the Māori iwi (tribe) Waitaha, whose tribal lands included the areas the Waitaha penguin are thought to have inhabited. "Our findings demonstrate that yellow-eyed penguins on mainland New Zealand are not a declining remnant of a previous abundant population, but came from the subantarctic relatively recently and replaced the extinct Waitaha penguin", said team member Dr Jeremy Austin, deputy director of the Australasian Centre for Ancient DNA. Archaeological remains indicate that early Polynesian settlers hunted the subspecies and that this, with possible additional predation by Polynesian rats and dogs, was a probable cause of extinction. As the local Māori people have no record of this subspecies, it is estimated to have perished between c. 1300 and 1500, soon after Polynesian settlers arrived in New Zealand. It was first described as a new species M. waitaha in 2009, but reclassified as a subspecies M. a. waitaha in studies from 2019 and 2022. After their extinction, their range was occupied by yellow-eyed penguins (now M. a. antipodes), previously most abundant further south in the subantarctic islands. The decrease in sea lion populations after human settlement may also have eased their expansion. Another coauthor, Dr Phil Seddon, said "these unexpected results highlight ... the dynamic nature of ecosystem change, where the loss of one species may open up opportunities for the expansion of another".
Megadyptes antipodes richdalei Richdale's penguin (M. a. richdalei) is an extinct island dwarf subspecies from the Chatham Islands. Last dated after the 13th century, it was hunted to extinction.
Description
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