The mighty acorn

During the Thanksgiving holiday, which I spent in the nation’s capital, there were widespread reports of an acorn “crash†there and in nearby Mid-Atlantic states. Thankfully, similar reports have not emerged in the Northeast and New England.

Perhaps more than any other, acorns are an essential food source for our wildlife in winter. White-tailed deer, black bears, eastern chipmunks, gray and red squirrels, wild turkeys, white-footed mice and ruffed grouse are among the many animals that depend on acorns to survive the season.

Squirrels are the most notorious for storing, or “cacheing,†acorns, but are in no way the only animals that do so.  Blue jays and red-bellied woodpeckers, for example, also store the nuts for later retrieval. Such behavior not only helps the animals survive, but also helps to propagate oak trees. Many acorns get left in the ground — possibly because the animals cannot relocate them — and sprout in the springtime.

Studies of squirrels suggest that some seeds, particularly the meat of acorns from white oaks, are eaten “on the spot,†while those from red oaks are most often transported and stored for later. At other times, the researchers found that squirrels ate only the top half of the red oak acorn. Apparently the bottom half has more unpalatable tannins, so there’s greater incentive for squirrels to feed on the white oak acorns.

Acorns are the largest nuts produced in the wild (a distinction that was held by chestnuts until the chestnut trees largely died out from our forests).  They are also considered “mast,†meaning that they are produced cyclically — some years in abundance and others less so. These “boom and bust†cycles have been tied to similar changes in the abundance of rodents, as well as animals that prey on them such as hawks and owls.

On the flip side, researchers at the Cary Institute of Ecosystem Studies in Millbrook and at Bard College have found that the occurrence of Lyme disease in humans peaks two years after seasons of abundant acorns.  The white-footed mouse, which feeds on acorns, is the main repository for the Lyme disease bacterium and a major host for the black-legged tick nymph. Nymphs that feed one year on abundant mice, picking up the disease, then transmit it the next year to humans.

Notes: This coming Saturday is the annual Lakeville-Sharon Christmas Bird Count.  For more information, contact Audubon Sharon at 860-364-0520.

Fred Baumgarten is a naturalist and writer. He can be reached at fredb58@sbcglobal.net. His blog is at thatbirdblog.blogspot.com.