Deer ticks and Lyme disease go hand-in-hand in some places. But you can’t always put the blame on Bambi. Because new research shows that the incidence of Lyme disease tracks less with the abundance of deer than it does with the disappearance of foxes. The study is in the Proceedings of the National Academy of Sciences. [Taal Levi et al., "Deer, predators, and the emergence of Lyme disease"]

To see where foxes come in, you have to look at the tick life cycle.

When deer ticks are young, they feed on small mammals like the white-footed mouse. It’s from infected rodents that the ticks pick up the bacteria that cause Lyme disease.

Foxes, of course, prey on mice and other small mammals. So fewer foxes means more mice, and potentially more disease.

To come up with that connection, researchers modeled the relative contributions of various animal populations in areas where Lyme disease is rife. And they found that, in New York State, for one, the incidence of Lyme could be directly predicted by the dearth of foxes.

The foxes were pushed out by coyotes, which have been on the rise since New York lost its wolves. Which were driven away by humans. Who now get bit by ticks.

—Karen Hopkin

[The above text is a transcript of this podcast.]