AUSTRALIA University of Tasmania - Scientists are trying a new way of tracking what penguins are eating, examining their droppings with DNA analysis. Usually, finding out what a seabird is eating relies on the analysis of stomach-content remains obtained through stomach flushing.
AUSTRALIA University of Tasmania - Scientists are trying a new way of tracking what penguins are eating, examining their droppings with DNA analysis. Usually, finding out what a seabird is eating relies on the analysis of stomach-content remains obtained through stomach flushing.
This technique is both invasive and logistically difficult. Now scientists in Australia are using DNA-based fecal analysis in a dietary study on chick-rearing macaroni penguins (Eudyptes chrysolophus) at Heard Island. Conventional stomach-content data was also collected, allowing comparison of the approaches.
Prey-specific DNA tests were used to detect dietary DNA in fecal samples and carefully examined and quantified. Of the 88 faecal samples collected, 39 contained detectable DNA from one or more of the prey groups targeted with DNA tests.
Krill (Euphausiid) DNA was most commonly detected in the early (guard) stage of chick-rearing, and detection of DNA from the small fish species Krefftichthys anderssoni and shrimp (amphipods) became more common in samples collected in the later stage.
These trends followed those observed in the penguins' stomach contents. In krill-specific DNA libraries the proportion of DNA from the two dominant krill prey species (Euphausia vallentini and Thysanoessa macrura) changed over the sampling period; again, this reflected the trend in the stomach content data. Analysis of prey DNA sequences in universal clone libraries revealed a higher diversity of fish prey than identified by examining stomach contents, but non-fish prey were not well represented.
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Conclusions
The present study is one of the first to examine the full breadth of a predator's diet using DNA-based fecal analysis. Overall, the ability of the DNA-based approach to detect variation in the diet of macaroni penguins indicates this non-invasive method will be generally useful for monitoring population-level dietary trends in seabirds.
