A next-generation sequencing study of arthropods in the diet of Laysan Teal (Anas laysanensis)

The critically endangered Laysan Teal Anas laysanensis (known as koloa
pōhaka in the Hawaiian language) in the Northwestern Hawaiian Islands has
wild populations on Kamole (Laysan Island), Kuaihelani (Midway Atoll NWR),
and Hōlanikū (Kure Atoll). The Laysan Teal faces a new risk on Sand
Island, Kuaihelani: non-target poisoning via a pending House Mouse Mus
musculus eradication. After mice were observed attacking and depredating
Laysan Albatross Phoebastria immutabilis (mōlī) in 2015, plans to
eradicate mice were developed to protect this seabird species. However,
this approach risks poisoning the Laysan Teal. To reduce exposure, teal
will be translocated during mouse eradication. Even so, there is a
potential risk of secondary poisoning for teal by ingesting arthropods
that feed on mouse bait. We therefore used next-generation sequencing
(NGS) to identify which arthropods teal consume. From August 2019 to
February 2020, we collected 71 fresh teal faecal samples on Sand Island,
and successfully extracted DNA from 21 samples. Via NGS, we found that
teal most frequently consume cockroaches (order: Blattodea), freshwater
ostracods (Cyprididae), midges (Chironomidae), and isopods
(Porcellionidae). To a lesser degree, teal also eat spiders (Araneae),
moths (Lepidoptera), beetles (Coleoptera), springtails (Entomobryomorpha),
thrips (Thysanoptera), and crabs (Decapoda). Notably, Sand Island’s teal
consume entirely different arthropods from teal on Kamole, which mainly
eat flies (Diptera) and brine shrimp (Anostraca, Artemia sp.). Our study
serves as a model for risk mitigation during invasive rodent eradications.