ACADIA NAT’L PARK — Ticks are much more abundant in parts of Acadia that burned in the October 1947 fire that swept across the eastern half of Mount Desert Island than in the areas that were spared.
That is a preliminary finding of research into the prevalence and distribution of ticks in the park.
“We’re trying to establish associations between where we see high densities of ticks and various environmental variables,” said Allison Gardner, assistant professor of biology and ecology at the University of Maine, who is leading the study.
“We’re conducting this research because we want to be able to inform visitors about where they are most likely to get exposed to ticks in the park, which can potentially help them protect themselves.
“We’ve also been collaborating with National Park Service staff with the goal of using our findings to inform landscape management strategies that the park could undertake to protect visitors against exposure to ticks.”
Deer ticks — also known as black-legged ticks — which are found in Acadia and throughout Maine, can carry the organisms that cause several serious diseases, the most prevalent being Lyme disease. The two other most common tick-borne diseases in Maine are anaplasmosis and babesiosis.
Gardner said the discovery that ticks are, in general, more likely to be found in areas of the park that burned in 1947 is not really surprising.
“We think the reason we’re seeing that pattern is that, since the fire, most of the vegetation in that area of the park is deciduous, and ticks generally seem to be more commonly found in hardwood forests than in softwood forests,” she said.
One reason for that, she said, is that mice and deer, the ticks’ primary host animals, tend to be found in greater numbers in hardwood forests.
“Another piece of it is that when ticks are off the hosts and just lying on the ground – which is about 95 percent of their life cycle — they are very sensitive about humidity,” Gardner said. “And in the hardwood and mixed wood forests, there tends to be a thicker layer of leaf litter, which is very good for preventing the ticks from [drying out], so they probably survive at a higher rate.”
Gardner said of the 1947 fire, “It’s really fascinating seeing that this disturbance that occurred more than 70 years ago is still having impacts that have potential implications for human health.”
Five times the ticks
Sara McBride, a UMaine graduate student, and a group of undergraduates were in Acadia last summer collecting ticks, which were then tested over the winter for disease-causing pathogens. The students are here collecting ticks again this summer.
So far, they have found about five times as many ticks this year as they did last year.
Gardner said that finding is likely related to the fact that an unusually large number of small mammals were seen in the park last summer.
“It’s been shown in various parts of the country that, generally, when you see a lot of small mammals one year, you’re likely to see a very high tick population the following year,” she said. “So, the good news is that next year we might have lower tick densities because small animal populations go through natural cycles, and this year we are seeing relatively few small mammals.”
So, this year’s big increase in ticks isn’t necessarily indicative of a trend.
“But there certainly has been a trend statewide and in Acadia of increasing abundance of black-legged ticks and cases of tick-borne illness over the past 20 years,” Gardner said.
Collaborating in the study is Sandra de Urioste-Stone, assistant professor of nature-based tourism at UMaine. She has been doing research on how Acadia visitors are or are not protecting themselves from ticks.
“We know from other research studies that have been conducted in the park … that visitors are really concerned about increased risk of tick-borne diseases, as is the park staff,” Gardner said.
Also involved in the tick research is Abe Miller-Rushing, Acadia’s science coordinator, and Rebecca Cole-Will, the park’s chief of resource management, along with a National Park Service epidemiologist based in Fort Collins, Colo.
Data gathering for the ticks-in-Acadia study is to be completed this fall.
“Hopefully, we will have findings to share in the next six months or so,” Gardner said.