With the risk of tick-borne diseases increasing in northern New England, scientists at the University of Maine launched a citizen science project in nine southern and coastal counties in 2020 to document tick species and estimated abundance on forested properties. The first year of data revealed that forest management and invasive species play a significant role in the abundance of ticks in an area.
“The black-legged tick or deer tick is fairly new to the state, and we’re seeing it spread in real time,” said Elissa Ballman, the research associate at the UMaine Vector Ecology Lab who is coordinating the project. “It’s becoming a real problem, and we expect it to get worse over time. It’s a forest-loving tick, and with 90 percent of Maine forested, we’re trying to come up with ideas for how to manage ticks so forest managers and users can be a little safer.”
In the first year of the project, 116 volunteers collected more than 1,600 ticks by dragging a white cloth across the ground in the forest, and 445 of the ticks were tested for pathogens. Twenty-five percent carried the bacterium responsible for Lyme disease, and the pathogens for two other diseases – anaplasmosis and babesiosis – were also detected.
Properties harvested for timber sometime in the previous two decades – whether it was one year ago or 20 years ago – had significantly fewer black-legged ticks. Ballman is still trying to figure out why. She said that it might have to do with the increase in sunlight that filters to the forest floor in recently harvested forests.
“Ticks are very sensitive to drying out, so they don’t want to be exposed to sunlight and wind,” she said. “It’s also possible that timber harvests have an impact on tick hosts like mice and other small mammals. The harvest could displace the hosts.”
The tick survey also found that properties with invasive plants and shrubs had many more ticks than properties with few invasives, perhaps because many invasive plants form dense, shady habitat that ticks prefer. Many tick hosts, such as mice, prefer a similar habitat. The invasive species that appeared to have the greatest influence on tick numbers were Japanese barberry, Asiatic bittersweet, buckthorn, and bush honeysuckle.
The volunteers also collected dog ticks, which did not appear to show the same pattern of abundance declines in recently harvested forests or increases in forests containing invasive plants. The researchers are also watching for Asian longhorn ticks and lone star ticks, two species that have not yet become established in Maine but that are increasing in abundance in southern New England.
Additional volunteers are sought to continue the tick surveillance program in the coming years. The researchers also plan to launch a related project to work with landowners and land managers to measure the immediate impact of land management strategies on ticks. Forest owners planning timber harvests or invasive species removal are encouraged to participate.