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 succe..., From August 2019 to February 2020, we collected 71 fresh faecal samples from Laysan Teal across six locations on the island. Faecal sample collection occurred weekly and involved 30 min surveys in areas where teal aggregate and faecal samples could be collected with minimal contamination (i.e. from concrete or asphalt surfaces with scant vegetation). Faecal samples were collected immediately after an individual was directly observed defecating. Upon collection, faecal samples were individually stored in vials of 70% isopropyl alcohol, labelled, and placed in a -20°C freezer until shipment to the mainland for further preparation. Our sampling pool consisted of 33 females, 31 males, and seven teal whose sex we could not visually confirm; most of the samples (55) came from individuals one year or older (AHY = after hatch year, SY = second year, ASY = after second year; 77.5%), 10 from hatch-years (HY; 14.1%), and six from teal of unknown age (8.5%).
For DNA extraction, we used the QIAamp P..., For ASV data: For arthropod ASVs, we filtered out all ASVs assigned to any phylum other than Arthropoda and provided the most precise level of taxonomic identity as possible. Data have not been normalized by total read counts per sample.Â