The prevalence in its diet of a single fish species raises concern for the resilience of the endangered hoiho and highlights the importance of measures such as the protection of marine habitats, University of Otago researchers say.
As a healthy diet had previously been shown to be important for breeding success and survival, the results were concerning, study co-author Ludovic Dutoit said.
‘‘Yellow-eyed penguins are known to be highly selective feeders, and traditionally their diet has consisted of a small number of fish and squid species,’’ Dr Dutoit said.
‘‘To find that their current diet is dominated by blue cod, and very few other prey species, is not what we would have liked to have found.’’
In a first for assessing the diet of New Zealand penguins, the hoiho research team based in the department of zoology used DNA analysis of hoiho faeces to reconstruct what they were eating.
Lead author and PhD candidate Melanie Young collected more than 300 faecal samples from hoiho along the Otago coast, and the research team extracted a specific gene found in all animals, known as mitochondrial 16S, to identify individual prey species in the birds’ diet.
The findings, published in Wildlife Research, identified that blue cod made up a large proportion of the penguins’ diet, occurring in all of samples and accounting for more than 55% of the DNA sequences identified.
Co-author Yolanda van Heezik, whose diet research in the 1980s indicated the delicate relationship between the diet quality, quantity, breeding success and survival of hoiho, was concerned about the absence in the diet of several key species that were available to hoiho in the 1980s.
Recent video footage also confirmed the absence of those fish in the marine environment where penguins foraged, she said.
‘‘Excessive reliance on one or very few prey species is unlikely to promote resilience in this beleaguered species, and highlights the importance of protecting marine habitats through the creation of marine reserves that encompass penguin foraging habitat,’’ Prof van Heezik said.
Dr Dutoit said DNA analysis of wildlife faeces offered a variety of opportunities for diet research involving a range of species in New Zealand.
The DNA approach, using penguin faeces collected from around nests while penguins were away at sea, had proven an efficient and non-intrusive way to capture baseline diet information that could be compared with future data collected.
Many more penguins could be sampled through collection of faeces than tracked using cameras, meaning DNA sampling of faeces was ideal for monitoring long-term diet trends of many individuals at multiple breeding sites.
While this approach did not reveal other important information about foraging, such as how much energy was required to catch and eat blue cod, it could be used in combination with other methods, such as animal-borne cameras, to provide a glimpse into what happens underwater.
- Staff reporter