Quarterly Wildlife Mortality Report
October 2015 to December 2015
Written and compiled by members of the U.S. Geological Survey National Wildlife Health Center - Wildlife Epidemiology & Emerging Diseases Branch.
Mouse predation on adult nesting albatrosses on Sand Island, Midway Atoll National Wildlife Refuge
During the annual albatross census in late December 2015 at Midway Atoll National Wildlife Refuge, counters observed a small and highly localized cluster of Laysan albatrosses (Phoebastria immutabilis) with wounds on the back of their necks. Close observation of the wounds and canvassing the entire area for evidence of incipient species (e.g., rats) or new behavioral interactions among existing species did not result in an obvious culprit. A monitoring program was implemented and revealed that the severity of wounds, number of impacted birds, and geographical area affected increased dramatically between December 23, 2015 and January 5, 2016. Based on consultation with wildlife biologists and wildlife health experts in Honolulu, it was suspected that resident mice were causing the damage. On January 5, U.S. Fish and Wildlife Service (USFWS) staff and volunteers deployed baited live traps and trail cameras to further investigate the cause of the neck and back wounds. Camera footage revealed that mice were repeatedly entering and staying in the feathers on the backs of nesting albatrosses for prolonged periods of time. Albatrosses on camera showed signs of agitation that included frequently standing up off their egg, shifting position on the nest, and repeated preening. A higher than normal level of adult mortality has been observed in this area, with the majority of fresh carcasses displaying open wounds to their back and/or neck. Additionally, nest failure due to abandonment was nearly twice the rate typically observed. Six fresh albatross carcasses were sent to the U. S. Geological Survey’s National Wildlife Health Center Honolulu Field Station on January 6 for necropsy. Results revealed that the birds were in excellent body condition with no obvious cause of death other than the wounds. Study of the wound sites confirmed rodent chewing. Similar findings were noted during necropsies of 24 additional birds performed on site by USFWS staff. Photographic evidence, coupled with necropsy findings, led to the conclusion that the bites occurred before death. Based on camera evidence and individuals found in the live traps, it was confirmed that the mice involved are house mice (Mus musculus), a species long-established on Sand Island, Midway Atoll. By January 20, two additional areas, located 400 m and 1000 m northeast of the original site, were discovered with dead and live bitten Laysan albatrosses. As of February 29, 2016, over 480 albatrosses have been observed with bites and 42 have been found dead in a 17,500 m2 area. Histology of birds with mouse bites indicated they are dying from sepsis. Article contributed by Meg Duhr-Schultz, U.S. Fish & Wildlife Service.
Amphibian populations worldwide face multiple serious threats, including chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd). A new chytrid fungus, Batrachochytrium salamandrivorans (Bsal), was recently discovered in association with severe mortality in European fire salamanders (Salamandra salamandra). Bsal likely originated from Asian salamander hosts and is believed to have been transported to Europe via international trade of salamanders for pets. The Bsal fungus has not been detected to date in the United States.
Scientists at the USGS National Wildlife Health Center (NWHC) recently published a risk analysis illuminating the threat posed by Bsal to amphibians in the United States. The analysis (Richgels et al. 2016. Royal Society Open Science) utilizes spatial data on imports and pet trade establishments, salamander species diversity, and characteristics of Bsal ecology to identify high-risk geographic areas with both a high likelihood of introduction and severe consequences for local salamanders. This risk assessment has supported the U.S. Fish and Wildlife Service interim rule, published in The Federal Register, which declared 201 species of salamanders from 20 genera as “injurious amphibians” because of their potential to carry Bsal infections. Under this interim rule, both importation into the United States and interstate transportation between States, the District of Columbia, the Commonwealth of Puerto Rico, or any territory or possession of the United States of any live or dead specimen, including parts, of these 20 genera of salamanders are prohibited, except by permit for zoological, educational, medical, or scientific purposes.
The NWHC-led risk assessment is also being used to guide an intensive Bsal surveillance effort in collaboration with the USGS Amphibian Monitoring and Research Initiative (ARMI). The NWHC plans to test samples from up to 10,000 wild salamanders collected throughout the United States during 2016 for presence of Bsal. In pilot work, the NWHC and ARMI tested over 500 salamander swabs from 37 sites on the West Coast, Gulf Coast, and Mid-Atlantic in 2015 and detected no Bsal. The NWHC continues to provide epidemiologic investigation and diagnostic services for wildlife mortality and morbidity events, and possesses a diagnostic permit to receive salamander species listed in the USFWS interim rule.
White-nose syndrome Winter 2015/2016 update
To date, white-nose syndrome (WNS) has been confirmed in bats from 27 states and five Canadian provinces within the eastern half of North America (Minnesota announced confirmation of WNS in St. Louis County in March 2016). Pseudogymnoascus destructans (Pd), the fungus that causes WNS, has also been detected in Mississippi, Nebraska, and Oklahoma, although no clinically-affected bats have been reported from these states. North American bat species confirmed positive for WNS include little brown bat (Myotis lucifugus), northern long-eared bat (M. septentrionalis), Indiana bat (M. sodalis), gray bat (M. grisescens), eastern small-footed bat (M. lebeii), tri-colored bat (Perimyotis subflavus), and big brown bat (Eptesicus fuscus). Of note, Pd has been detected in the hibernaculum environment and on bats from multiple sites across China (Hoyt et al. 2016. Emerging Infectious Diseases).
The USGS National Wildlife Health Center (NWHC) continues to lead a 3-year surveillance project designed to assist State and Federal wildlife agencies nationwide with early detection of Pd in new areas, and to address specific research priorities identified by partners in conjunction with the White-Nose Syndrome National Plan. During the first two years of the project swabs from more than 2,100 bats, representing 16 North American species, and 580 environmental substrates from 110 hibernacula in 23 states were returned to the NWHC for analysis. This project has resulted in the detection of Pd at 16 hibernacula of previously unknown Pd status in six states, including nine sites where there was no physical or behavioral evidence of WNS observed in the bat population. Nearly all detections of Pd originated from swabs collected from bats rather than from environmental substrates collected inside of hibernacula. Information on biotic and abiotic factors continues to be collected at all hibernacula surveyed to assess the potential importance of various parameters in contributing to presence of Pd.
Partners are reminded that the NWHC continues to provide diagnostic and epidemiological assistance to investigate unusual bat mortality events. Federal, State, or Tribal agencies wishing to participate in the expanded national Pd surveillance strategy should contact Dr. Anne Ballmann at the NWHC (608-270-2445, email@example.com).
Snowy owl mortalities in Wisconsin
Between mid-November 2015 and the end of January 2016, 10 snowy owl (Bubo scandiacus) carcasses collected in Wisconsin were submitted to the USGS National Wildlife Health Center (NWHC). All were juvenile birds suffering from advanced emaciation. Although multiple etiologies were detected, including Salmonella sp., Aspergillus sp., Escherichia coli, organophosphate exposure, and trauma, the cause of death in the majority of birds was determined to be multiorgan failure secondary to emaciation.
The NWHC is a partner in Project SNOWstorm, a collaborative endeavor between numerous State and Federal agencies, academia, and non-governmental organizations that was originally conceived by the Maryland Department of Natural Resources. Formed in the wake of the historic snowy owl irruption of 2013-14, the goal of this project is to expand knowledge regarding the ecology of wintering snowy owls.
Snowy owls are native to Arctic regions of North America and Eurasia. They nest in the summer primarily north of 60 degrees north latitude. Their primary food source is small mammals, but they are also known to prey upon multiple bird species, including waterfowl, gulls, shorebirds, songbirds, and other raptors. Some individuals overwinter on the breeding grounds, but many birds migrate farther south in response to reduced prey availability during winter months. Irruptions, or larger than normal winter migrations of snowy owls into more southern latitudes, occur periodically in apparent response to resource shortages and may also reflect higher than normal reproductive success the previous summer. The extreme irruption that occurred in the winter of 2013-14 is thought to be the largest migratory event of snowy owls in the Northeast and Great Lakes regions in a century. Smaller scale irruptions subsequently occurred during the winters of 2014-15 and 2015-16.
To view, search, and download historic and ongoing wildlife morbidity and mortality event records nationwide visit the Wildlife Health Information Sharing Partnership event reporting system (WHISPers) online database: http://www.nwhc.usgs.gov/whispers/
To request diagnostic services or report wildlife mortality: http://www.nwhc.usgs.gov/services/