New Zealand’s hoiho, the yellow-eyed penguin already perched on the edge of extinction, is in fact three genetically distinct subspecies, according to a landmark genomic study published in Nature Ecology & Evolution overnight that warns the mainland line could vanish within a decade unless conservation efforts are reshaped around the finding.
The research, led by Professor Jemma Geoghegan at the University of Otago alongside the Department of Conservation, Ngāi Tahu and Genomics Aotearoa, sequenced complete genomes from 249 penguins across the species’ range. It found three deeply isolated lineages that have not interbred for thousands of years, well before humans arrived in Aotearoa.
The three populations are proposed as hoiho murihiku for the mainland and Rakiura birds, hoiho motu maha for the Enderby and Auckland Islands group, and hoiho motu ihupuku for the Campbell Island population. The names were developed in partnership with Ngāi Tahu and reflect the geography that has shaped each lineage.
Mainland birds split from the southern populations between 5,000 and 16,000 years ago, the study found, and the three groups have remained isolated since. There has been no migration between them and each has adapted independently to its own oceanic territory.
“This means the critically endangered northern population is not simply a recent extension of the southern populations, but a distinct evolutionary lineage in its own right,” Professor Geoghegan said.
The genetic findings carry an immediate, hard edge for conservation. Fewer than 115 breeding pairs remain on the mainland and Rakiura, and fewer than 20 per cent of chicks are surviving to adulthood. Since 2019, mainland chicks have been dying from a respiratory distress syndrome linked to a newly identified gyrovirus that Geoghegan’s lab first sequenced in 2023.
The genomic data also helped researchers pinpoint why mainland chicks are dying while their southern cousins are not. By running genome-wide association studies, the team identified candidate immune and respiratory genes tied to disease susceptibility, including genes involved in antiviral responses. The virus is present across all three populations, but the worst illness clusters in the small, increasingly inbred mainland group.
The paper, with first author Joseph Guhlin and colleagues, notes that mainland birds may be especially vulnerable to the virus because of their unique evolutionary history and shrinking population size, as reported by RNZ.
Until now, conservation managers had treated the loss of mainland breeding birds as a problem that could, if necessary, be backstopped by translocating birds from healthier subantarctic colonies. The new genomic picture closes that door. Moving Auckland Island or Campbell Island birds to the mainland would dilute thousands of years of local adaptation and could disrupt traits that have evolved for the specific conditions of each site.
The Otago-led team said the work strengthens the case for keeping each subspecies separate and managing them as distinct populations rather than one declining species.
Hoiho are among the world’s rarest penguins. They breed only in New Zealand and are easily recognised by the pale yellow band of feathers running from the eye to the back of the head. They prefer to nest in dense coastal forest or shrubland and forage close to shore for fish and squid, which makes them unusually sensitive to set-net bycatch, marine heatwaves and warming nearshore waters.
The Department of Conservation has been working with Ngāi Tahu and groups including the Yellow-Eyed Penguin Trust on intensive nest monitoring, predator control and chick rehabilitation along the Otago and Catlins coasts for more than a decade. Even with this effort, the mainland count has continued to fall, and last summer’s breeding season recorded one of the lowest chick fledge rates ever measured.
The new paper does not propose a single silver-bullet intervention. Instead, the researchers list a stack of measures that they say all need to happen at once. Stronger fisheries rules to reduce bycatch sit at the top of the list, alongside expanded predator control on mainland nesting sites, more chick rehabilitation capacity, sustained disease surveillance and genome-informed breeding decisions. They also call for action on the underlying marine ecosystem changes that are reshaping the food the penguins depend on.
For Ngāi Tahu the work also carries a cultural weight. Hoiho are a taonga species, depicted on New Zealand’s five-dollar note, and the new tripartite naming embeds mana whenua in the way the birds will be described in scientific literature for decades to come.
The findings were also covered by Oceanographic and summarised by Sci.News, both of which highlight the divergence dates and the proposed three-way classification. The full paper is published as Guhlin et al. in Nature Ecology and Evolution.
Without urgent intervention, the researchers warn, the mainland hoiho lineage could be gone within a decade. That would not just be the loss of a population, but the erasure of an evolutionary lineage that has been shaping itself to the southern South Island coastline for between 5,000 and 16,000 years.
What do you think New Zealand should be prioritising to save the mainland hoiho? Share your thoughts in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂
Leave a Reply