Decades of research confirm it: Ticks pick up Lyme bacteria from mice and other small animals — not deer.*

Research does not support reducing deer numbers as a way to lower Lyme disease risk

1) 35 years of data confirm it: deer aren’t the driver of Lyme risk

For decades, deer were assumed to be central to Lyme disease ecology because adult ticks are often found on them, as well as on other animals. Long-term data tell a different story.

In August 2026, Cary Institute disease ecologist Richard Ostfeld and colleagues published a synthesis of more than 35 years of continuous field data — one of the longest-running ecological studies of its kind. Earlier analyses using shorter stretches of that same dataset had detected a weak statistical link between deer numbers and the abundance of nymphal ticks. With the full 35-year dataset, that link disappeared entirely.

“We had detected a weak positive relationship between deer and subsequent nymph abundance over short subsets of the data, but the whole data set in its entirety shows no such thing.”

Richard Ostfeld, Cary Institute disease ecologist

The strongest predictors that emerged instead were the same ones seen throughout this research: acorn crops, which drive booms in white-footed mouse populations, and mouse abundance itself — a strong mouse year increases the following year’s tick numbers by roughly 40%.

Ostfeld et al., “The Ecology of Lyme Disease: Long-Term Data, Surprises, and a Synthesis,” Proceedings of the National Academy of Sciences 123(34): e2610907123 (2026). DOI: 10.1073/pnas.2610907123

2) The CDC review: no evidence it works outside islands and peninsulas

“There is insufficient evidence to recommend deer population reduction as a Lyme disease prevention measure, except in specific ecologic circumstances.” (e.g. isolated islands and peninsulas)

Kugeler, Jordan, Schulze, Griffith & Mead, Zoonoses and Public Health (2016). Will Culling White-Tailed Deer Prevent Lyme Disease?

Where deer reduction has been shown to work, it has meant removing nearly all the deer from a small, isolated site. At Great Island, roughly 85% of the herd. Nothing comparable has been shown in an open community where deer migrate in and out.

3) A 2012 study showed that when fox populations dropped and deer populations stayed the same, Lyme disease rose

Foxes eat white-footed mice, the primary Lyme reservoir. Fewer foxes. More mice. More infected ticks.

A 2012 study in the Proceedings of the National Academy of Sciences found that as red fox populations fell across the Northeast and Midwest, Lyme disease cases rose. Deer numbers didn’t explain the pattern — in the same areas, Lyme incidence was uncorrelated with deer abundance, and in some states was negatively correlated with it.

What changed was the number of mice, not the number of deer.

Levi, Kilpatrick, Mangel & Wilmers, “Deer, predators, and the emergence of Lyme disease,” PNAS 109 (2012): 10942–10947.

What about lone star ticks?

A second tick, the lone star, is a different animal. It can cause alpha-gal syndrome, an allergy to red meat. The research above concerns blacklegged ticks and Lyme disease, and it should not be stretched to cover lone stars.

Lone stars are generalist feeders, moving among many hosts rather than depending on one. Larvae and nymphs feed on deer, ground-dwelling birds, and on small and medium mammals — raccoons, skunks, rabbits — and unlike blacklegged ticks, lone stars bite people directly at every life stage.

The same limitation applies here as with Lyme: reducing any single host species only affects tick numbers when the reduction is extreme, and partial reduction simply concentrates ticks on the animals that remain (see number 2 above).

With so many hosts in the mix, no single animal is the lever.

Personal protection works against both species, and innovations are on the horizon.