U.S. Geological Survey (USGS) researchers at the Massachusetts Cooperative Fish and Wildlife Research Unit, on the campus of University of Massachusetts, are partnering with Maine Department of Inland Fisheries and Wildlife, University of New Hampshire, and the Penobscot Nation, to monitor winter tick distribution and abundance and help understand effective adaptation and mitigation strategies to prevent negative effects on moose populations.

Under the leadership of the Penobscot Nation and with technical support from the USGS, researchers have co-created an effective method for monitoring winter tick distribution and abundance in brushy moose habitat. Researchers reviewed the tick literature and found common analysis methods lacked rigor and developed an effective way to analyze a common type of tick abundance data gathered from flag/drag surveys.

Winter ticks and moose are both native species in North America, but a combination of recent warming trends, forest management, and abundant moose populations may be interacting to create a new dynamic between them in New England. The link between high moose density and high tick density is clear, but researchers are uncovering evidence that mild winters and warm summers may be influencing super-abundances (called epizootics) in central Maine, northern New Hampshire, and northern Vermont. Moose living at the warmer southern extents of the moose distribution, where ticks should thrive (e.g., Massachusetts), are largely escaping the devastating effects observed further north. This could indicate that an interaction between climate conditions and moose density may affect how bad infestations are in any given moose population.

The ticks strike at a time of nutritional stress for moose and the onslaught makes many too weak to survive. When adult female ticks attach and take a large blood meal to support egg production, they expand up to three times their body size (from ~5 mm to ~15 mm). The sheer number of ticks feeding on the moose can collectively remove up to seven gallons of blood from moose during severe tick infestations. This leaves the moose anemic and thin. Weak moose, especially calves, will die, but adults can and do also succumb to the ticks. Infected individuals often attempt to rid themselves of the tiny irritants by biting, scratching, or rubbing on trees, stripping off most of their hair in the process leaving them with their ghostly appearance. This loss of hair can lead to hypothermia during spring, which often coincides with cold and snowy weather.

For the next steps, the researchers will combine tick monitoring with data from a regional camera trapping array. To understand potential drivers of epizootics at an unprecedented, regional scale. The researchers hope to combine this with experiments designed to pinpoint the mechanisms that drive tick survival and may inform mitigation strategies.

The ONB features articles from Cooperative Fish and Wildlife Research Units across the country. Working with key cooperators, including WMI, Units are leading exciting, new fish and wildlife research projects that we believe our readers will appreciate reading about. This story is authored by Tammy Wilson, a USGS Research Ecologist and Assistant Unit Leader at the Massachusetts Cooperative Fish and Wildlife Research Unit at the University of Massachusetts, Alexej Sirén, wildlife ecologist at the University of New Hampshire, and Juliana Berub a previous graduate student on the project and now a biologist at the U.S. Fish and Wildlife Service. Benjamin Simpson is the Wildlife Resource Manager for the Penobscot Nation. Lee Kantar is the Moose Biologist with Maine Department of Inland Fisheries and Wildlife.