Imagine coming upon a stick floating in a large pond only to discover the “stick” had a head and tail and was making a beeline for the shore. The fact that an Eastern Gray Squirrel (Sciurus carolinensis) had paddled half a mile to get from one shore to the opposite shore of a pond shouldn’t have come as such a surprise, as this rodent has a long history of migratory swimming behavior, but it’s such an incongruous and unexpected event that it made my companion and me initially question our eyesight and then laugh out loud.
Historical reports suggest there have been many massive Eastern Gray Squirrel migrations in the United States, beginning in 1749 in Pennsylvania. Records show the state paid three cents for each squirrel killed; over 640,000 squirrels were turned in for bounty. One migration from Wisconsin in 1842 lasted four weeks and involved a half billion squirrels. Because of the numerous squirrel migrations, John James Audubon was erroneously convinced that the squirrels on the move were a separate species from the Eastern Gray Squirrel and gave them the scientific name Sciurus migratorius. (This proved to be inaccurate.)
During the 1800’s, thousands of squirrels would periodically move en masse across roads, fields and forests, and swim across lakes and rivers (including the Mississippi and Connecticut Rivers) in an effort to disperse. The consensus is that these mass movements were a response to local food conditions. They occurred mostly during the month of September following a year in which there was a large production of food (acorns).
The most recent mass migration of Eastern Gray Squirrels in eastern U.S. occurred in 1968, when a bumper crop of acorns in 1967 was followed with a corresponding bumper crop of young squirrels in 1968. By fall, as the first litter of the year left the nest, there was a severe shortage of food. As a result, massive numbers of acorn-eating squirrels dispersed in search of food.
One Eastern Gray Squirrel swimming across a New Hampshire pond does not a migration make, but it might not be a bad idea to keep an eye out for excessive numbers of paddling squirrels and/or road-killed rodents come September. (Photo by Erin Donahue)
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Red Squirrels are active year round and have nests that they can retreat to at any time of the year. These nests are used for shelter and rest, for over-wintering and as brood chambers. Red Squirrels build them in a variety of spots (tree cavities, old woodpecker holes, middens, rock piles, rotting logs, tree canopies) with a variety of material (twigs, branches, leaves, shredded grape bark, etc.).
Regardless of where they build their nest or what they build it with, Red Squirrels line it with fine, relatively soft material, such as grasses, bark fibers, feathers and fur. If a Red Squirrel happens upon potential nest-lining material, including an old dog towel hung out to dry, it will readily chew it into shreds and carry them back to its nest.
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There is a marked seasonal difference in the Red Squirrel’s appearance due to its two annual molts (spring and fall). In the winter, a broad rusty-red band extends along its back, from its ears to the tip of its tail. The Red Squirrel’s thicker winter coat also includes ear tufts, which no other species of squirrel in the Northeast possesses. Come spring, when the squirrel sheds again, it loses its ear tufts and its new coat is closer to an olive-green color than red.
In the fall, Eastern Gray Squirrels bury individual acorns from Red and White Oaks to sustain themselves through the winter. The acorns of Red Oaks have delayed germination – they can be stored up to six months before they start germinating. The acorns of White Oaks, however, have no such dormancy, and begin to germinate in the fall, soon after they fall from the tree. Once acorns sprout, they are less nutritious, as the seed tissue converts to the indigestible lignins that form the root. Gray Squirrels, as a means of “long-term cache management,” selectively remove the embryos from White Oak acorns (but not from Red Oak acorns) before burying them. Germination is prevented, and the storage viability of the White Oak acorns is extended by six months, equaling that of the Red Oak acorns.
Red and Gray Squirrels remain active year round, and thus, need to have access to food throughout the year. In order for this to happen, seeds and nuts must be stored in the warmer months for consumption during the winter and early spring, when food is much harder to find. While Gray Squirrels tend to bury nuts and seeds individually for this purpose, Red Squirrels often cache numerous seeds (mostly conifers and maples) in one spot, dispersing these caches throughout the woods. During the winter Red Squirrels use their memory (and sometimes their sense of smell) to locate these buried treasures. Inevitably some are overlooked and in many of these cases, the seeds germinate. Finding little patches of multiple seedlings, such as this miniature stand of young Sugar Maples, is a good indication that at least one Red Squirrel overwintered in the vicinity.