Here are the species we talk about when we talk about Lyme disease:
First, the black-legged ticks that carry the Lyme bacteria from species to species. Second, the white-footed mice and other little scurrying mammals that provide one reservoir for the bacteria. Third, the white-tailed deer that provide the ticks a blood meal and transportation around the landscape. And finally, the humans, who get sick when a tick bites them and infects them with the Lyme bacteria.
Now there are two more: coyotes and red foxes.
These two predators, and their hostile relationships, may be another key in understanding the disease. At the very least, thinking about them shows how deeply complex our ecology can be. Taal Levi, a postgraduate student at the University of California at Santa Cruz -- who is now at the Cary Institute of Ecosystems Studies in Millbrook, N.Y. -- is the researcher establishing the fox-coyote-Lyme link. Levi's proposition is this:
White-footed mice, along with other rodents, are a crucial link in Lyme disease transmission. They carry the bacterial spirochete Borrelia burgdorferi, which causes Lyme disease in humans. Red fox are great predators of those rodents -- mice are the main ingredient in a fox diet. Where there are many foxes, there are fewer white-footed mice and, maybe, fewer cases of Lyme disease. But on the East Coast, there is a new predator on the scene: coyotes.
Paul Rego, a wildlife biologist with the state Department of Energy and Environmental Protection, said since the 1960s coyotes have slowly infiltrated the Eastern United States from the West. They hadn't been here before that, Rego said, but they're common in the state now. Foxes and coyotes don't get along. "Coyotes kill red fox," Levi said. "When we put radio collars on red fox, we find they avoid places where there are coyotes."
Rego said there are no studies showing coyote versus fox numbers in Connecticut, nor any studies showing foxes on the decline in the state. "But I am aware of the studies that show coyotes exclude red fox from their territories," Rego said. Therefore, he said "it's quite plausible" to think that as coyote numbers in the state have gone up, fox numbers have gone down. And coyotes aren't as good as foxes at cleaning the landscape of rodents. They eat them. But Levi said the territories that coyotes establish are much bigger than foxes'. Foxes require two to four square miles for their territory. If there's plenty of food, they can make do with a square mile. Coyotes need five to 25 square miles.
Levi has studied the interactions of the two animals."We find that places that have more coyotes and fewer fox have more Lyme disease," Levi said. That applies not only to places like Connecticut along the East Coast, but also Great Lakes states like Wisconsin, where there is a high incidence of Lyme. Levi said it may also be time to downgrade the role deer play in the Lyme landscape.
"There is almost no Lyme disease in western New York," he said. "There are lots of deer there."