The New York Times let five biologists and entomologists debate the issue. The first guy out, Thomas Mather, professor of public health entomology, gave the answer that has become commonly lore: deer. The premise: Deer populations have risen along with lyme disease cases.
But then other scientists basically cast some reasonable doubt on the case against the deer. Ixodes scapularis, commonly known as deer ticks, bear ticks or black-legged ticks, can pick up the bacteria that causes lyme disease from a whole range of animals, not just its namesake. The American Lyme Disease Foundation calls deer this species’ “preferred host” but notes that mice are the primary carriers of the disease, which can also be spread via birds, dogs, cats, horses, squirrels and other small mammals.
Richard S. Ostfeld, of the Cary Institute of Ecosystem Studies, notes that the incidence of lyme disease and deer don’t correspond, but that acorn crops (which feed white-footed mice) do. William L. Krinsky, entomologist at Yale’s Peabody Museum, says we don’t have enough data to understand how much blame rodents and deer should get.
Interestingly, two species come out as heroes. Bard biology professor Felicia Keesing cites the Virginia opossum (Didelphis virginiana) as the under appreciated fighter of lyme disease; these guys attract and kill ticks by the thousands. Ostfeld gives some credit to owl, who eat the mice, who carry the disease.
Why is it important which species is to blame? Because when people think deer are to blame, they want to get rid of them. I have a reasonable, educated friend who supports getting rid of deer on Long Island because she’s afraid of lyme disease. Lyme disease–along with car crashes and eaten gardens, are used to drum up support for deer hunts. If white-tailed deer had any kind of PR muscle, they’d follow the example of pig farmers after the outbreak of swine flu–sorry H1N1–and lobby for changing the deer tick’s name.