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NO.7 JUNE 2016

HONOLULU FIELD STATION A newsletter of the Field Station, part of the USGS-National Wildlife Health Center in Madison, WI Focus: Mice predation on Laysan National Wildlife Refuge is one of the world’s most important breeding sites for (LAAL). In late December, 2015, refuge biologists noticed adult nesting LAAL with lesions on their head, neck and back. Consultations of refuge staff with HFS led to the suspicion that mice or rats could be responsible based on photos from published papers showing a similar phenomenon. The first wounded were observed during an annual albatross census at the end of December 2015. Remote night time photography by the refuge confirmed that non-native house Mouse on a Laysan albatross’s back (left), and head wound on mice (Mus musculus) were crawling over, chewing on and another nesting albatross (right). Photo credit © Meg Duhr-Schultz (left) harassing LAAL at night. In all, more than 300 nesting adult and Thierry Work (right). LAAL were attacked by mice, of which 48 died. At least 46 nests were abandoned. Black-footed albatrosses were also found injured, although in lower numbers. Necropsies performed by USFWS and HFS showed that adult LAAL were dying Number of birds from a combination of stress and bacterial infections secondary to open necropsied wounds becoming infected. All this prompts the question as to why Duck: Laysan Goose: Hawaiian Nene mice that have been on Midway for decades are suddenly eating adult Albatross: Laysan albatross. Refuge staff are implementing mouse control measures in Duck: Hawaiian Coot: Hawaiian heavily impacted areas to decrease incidence of mouse attacks on Moorhen: Hawaiian common Plover: Pacific Golden nesting birds. Options for mouse eradication are also being explored. Stilt: Hawaiian Booby: Brown Petrel: Hawaiian Dark-rumped Honolulu Field Station Necropsy Report 2015 Duck: Mallard/Hawaiian hybrid Duck: Muscovy Honeycreeper: Apapane One of our main duties here at the HFS is to perform necropsies on Junglefowl: Red mainly endangered species submitted to determine cause of death. In Shearwater: Newells Crow: Marianas 2015, the HFS received a total of 176 birds. Notable cases included Flycatcher: elepaio Hawk: Hawaiian diagnoses of malaria in an Iiwi (), lead poisoning in a Nene goose Honeycreeper: Iiwi (), liver disease in a Kauai Amakihi (Kauai), gout in a Newell’s Honeycreeper: Kauai Amakihi Owl: Hawaiian Short-eared shearwater (Kauai), a connective tissue tumor in a Nene goose Phalarope: Red Shearwater: Wedge-tailed (), and avian pox in a Nene gosling (Hawaii). Botulism continues Storm-Petrel: Leachs to be a leading cause of death. 0 12.5 25 37.5 50

Wildlife Health ridge to reef: Service- Research- Outreach NO.7 JUNE 2016

Mariana Crow Death Mystery Mariana crows are one of the most endangered crows in the world. Populations of this bird were historically on Rota and , but were extirpated from the latter because of predation by the brown tree snake. Since then, the only remnant population of this bird is on Rota where numbers have been steadily declining because of unexplained poor survivorship of immature crows. Predators like crabs, rats, feral cats, habitat destruction and disease are suspected causes of this decline. Crow habitat on Rota has been protected since 1994, and removal of non-native predators from core breeding habitat is being implemented. Understanding causes of death in Mariana crows is complicated by the remoteness of the island, difficulty in detecting dead birds, and shipping them to laboratories to determine cause of death. Recently, however, due to concerted efforts by field biologists on Rota, the HFS has received a few carcasses of immature Mariana crows in suitable post-mortem Mariana crow. condition. Necropsies of 4 crows have revealed a consistent pattern of massive inflammation Photo credit © University of of the liver and lung suggesting that crows might be dying from an infectious disease or, less Washington, RABEP Field Station, Rota, Northern plausibly, some sort of toxin. An infectious disease amongst immature Mariana crows may Mariana Islands thus explain why the birds have been declining on Rota, and this needs to be ruled out. HFS is currently collaborating with a variety of laboratories to determine what might be causing these lesions in immature Mariana crows. Toxoplasmosis Update Toxoplasma gondii is a parasite transmitted by feral cats. In Hawaii, the parasite was partially responsible for extirpation of the island’s only native crow (Alala) from the wild and has occasionally killed native birds like Hawaiian geese, Hawaiian coots, red footed boobies, and even non-native birds like francolins. Toxoplasma gondii has also killed Hawaiian monk seals. A recent paper (1) shows that T. gondii is probably widespread on the islands with up to 40% of native Hawaiian (nene) geese being infected on Maui, , and Kauai. Interestingly, new research is beginning to show that T. gondii can affect behavior of animals it infects. For instance, infected rats lose their fear of cats, and infected humans become more reckless and are more prone to accidents. Indeed, wildlife studies in Australia showed that animals infected with the parasite were more likely to die from traumatic episodes. Here in Hawaii, trauma (cars, flying into objects) is the most important cause of death in nene. In addition to polluting the environment with their feces and parasites, feral cats also kill native birds directly through predation. All this is unfortunate for Hawaii’s native wildlife. One inexpensive option to manage the effects of feral cats is through responsible cat ownership, such as keeping cats indoors. (1) Work TM, Verma SK, Su C, Medeiros J, Kaiakapu T, Kwok OC, Dubey JP (2016) Toxoplasma gondii antibody prevalence and two new genotypes of the parasite in endangered Hawaiian geese (Nene: Branta Sandvicensis). J Wildl Dis 52:253-257.

CONTACT Dr. Thierry Work USGS-NWHC-HFS PO Box 50187 Honolulu, HI 96850 808/ 792-9520 E-mail: [email protected]

Wildlife Health ridge to reef: Service- Research- Outreach