Parasites, snails may factor in Adirondack moose decline

August 9, 2017 by Blaine Friedlander
Tyler Shaban '17, left, and Jailene Hidalgo '18 conduct research in the Adirondacks. Credit: Cornell University

The apparent declining moose population in New York 's Adirondack Mountains may be caused partly by tiny parasite-transmitting snails eaten by moose as they forage vegetation, according to new research presented by two Cornell undergraduate students at the annual Ecological Society of America meeting, in Portland, Oregon, Aug. 8.

"Our results show that moose foraging in areas with high soil moisture may likely encounter higher densities of gastropods – snails and slugs – which likely increases the risk of parasitic threats from deer brain worm if the snails are eaten," said Jailene Hidalgo '18. Soil moisture had a strong effect on snail abundance, while variables such as soil pH, soil temperature and habitat type made little difference.

Said Hidalgo: "Since moose make use of water areas and eat in wet, dense pine forests, they're susceptible to a large presence of gastropods that pose a greater risk of Parelaphostrongylus tenuis transmission when white-tailed deer occupy the same space."

Hidalgo and Carlos Fernandez '19 work in the laboratory of Angela Fuller, associate professor of natural resources, and leader of the New York Cooperative Fish and Wildlife Research Unit.

After being absent for more than a century, moose returned to the Adirondacks in the 1980s. The New York Wildlife Health Program – in which the Wildlife Health Lab at Cornell's College of Veterinary Medicine participates – conducted surveys in 2016 on 11 live moose and 22 necropsies and concluded parasites are a major threat to the moose . As of 2010, New York state wildlife biologists had put the Adirondack moose population at 800.

Moose populations in nearby states such as New Hampshire are declining, leading scientists in New York to investigate the apparent decline in the Adirondacks. Last spring Fuller and her colleagues published New York moose occupancy estimates through hunter surveys. Fuller and other researchers in New York are currently studying the population size of moose and aim to monitor the animals through time.

Deer and snails both host the parasite, but they themselves are unaffected by it, Hidalgo said. The parasites' eggs hatch in a deer's brain, travel through its respiratory system to the gastrointestinal tract, finally exiting through feces as worm larvae. Snails feed on the mucus membrane of the worm larvae. Foraging then ingest infected snails, culminating in a diseased brain and spinal cord, and occasionally death. New York wildlife pathologists have confirmed cases.

On the same project, Fernandez sought to understand the best snail and slug trapping methods to assess parasitic threats. In addition to visual tree searches, three different trap types were set up and tested: pitfall ground traps, cardboard ground traps and water bottle tree traps.

Cardboard ground traps captured three times as many snails and slugs than did the ground pitfall traps. Statistically, there was no significant difference in capture rates between the bottle and visual searches. "Understanding the snail population can lead to improved abundance estimates, which can be used to further assess the health of the in New York," Fernandez said.

Hidalgo's poster, "Environmental Factors Influencing Gastropod Abundance: Implications of Parelaphostrongylus tenuis for Moose in the Adirondacks," will be exhibited, as will Fernandez's poster, "Gastropod Sampling Methodologies for Assessing Parasitic Threats to Moose in the Adirondacks."

Explore further: Moose tracking: There's an app for that

More information: Nathan J. Crum et al. Estimating occupancy probability of moose using hunter survey data, The Journal of Wildlife Management (2017). DOI: 10.1002/jwmg.21207

Related Stories

Moose tracking: There's an app for that

April 10, 2017

Ecologists in the University of Alberta's Department of Biological Sciences have developed an app to improve population modeling for moose, asking hunters record the number of moose they see while hunting in Alberta.

Moose multiplying in Scandinavia

April 20, 2008

Biologists say there are now record numbers of moose in Scandinavia -- the greatest population since the Ice Age.

Maine, packed with moose, didn't have so many ticks

May 15, 2015

Maine's state animal—the moose—fared better with potentially deadly ticks this past winter than in previous years, but the herd remains imperiled by the parasites in northern New England and beyond, wildlife biologists ...

Black bears on the move in upstate New York

April 27, 2017

The black bear population in southern New York has grown and expanded their range since the early 1990s, which has led to increased encounters with humans. But details about bear populations in the state have remained understudied.

Recommended for you

The astonishing efficiency of life

November 17, 2017

All life on earth performs computations – and all computations require energy. From single-celled amoeba to multicellular organisms like humans, one of the most basic biological computations common across life is translation: ...

Unexpected finding solves 40-year old cytoskeleton mystery

November 17, 2017

Scientists have been searching for it for decades: the enzyme that cuts the amino acid tyrosine off an important part of the cell's skeleton. Researchers of the Netherlands Cancer Institute have now identified this mystery ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.