Nature Notes by Dr. Frank Lang
When I was out for my usual early morning walk with Inu (my dog) we saw one of his favorite animals, rating close, I think, to the neighborhood cats. It was a western gray or silver-gray squirrel, Sciurus griseus, a common, handsome west coast mammal. Dog and I both fume when our native silver-grays get into our bird feeder to help themselves to sunflower seeds. Our silver-gray encounter this morning inspired me to resurrect this Nature Note.
Our gray squirrels occur in mixed broad-leaved coniferous woodlands and spend their daylight hours out doing squirrel things. They groom, explore, feed, play, loaf, try to stay out of harm’s way, and in January and February indulge in one of their few group social activities, mating. Mature gray squirrels seldom get together for s-e-x. If you see a mid- to late-winter crowd, you may prefer to exercise viewer discretion and avert your eyes. The crowd consists of several amorous males and a willing and able female. After mating they go their separate ways. The female nests in a tree cavity to give birth and raise her two to four young. The males, like some humans, don’t lift a finger. They don’t gather nuts for the family. They don’t repair the nest. They don’t pay alimony or child support.
Mature squirrels nest alone in stick nests called drays high in trees. In winter they construct a protective leafy roof. In summer they air condition by roof removal. Gray squirrels are active year-around, but will stay in during truly rotten weather. They are out just after sunrise for about an hour. By noon many squirrels retreat to their individual nests until late afternoon, when they are out again for several hours. Gray squirrels are not night owls. Most return to their nests an hour before sunset to spend a safe and quiet night.
Gray squirrels are scatter-hoarders. They bury acorns and nuts, then attempt to find them later using their keen sense of smell. They are also fond of underground truffle-like fungi, which they eat fresh, in great abundance, in the spring. Squirrels in their mushroom searches dig many of the small holes we see in our oak woodlands. They may play an important role in woodland ecology by distributing mycorrhizal fungal spores as they poop around the woods.
All is not sweetness and light in squirreldom. Native predators include bobcats, coyotes, foxes, and the occasional red-tail hawk. Non-native predators include Fido (read Inu here, if he had half a chance), Kitty, Honda, Buick, and Chevrolet. Gray squirrels are also considered a game animal in Oregon and are hunted by humans.
Various parasites afflict gray squirrels: mange, ringworm, ticks, mites, roundworms, and seven kinds of fleas. Parasites may account for long-term fluctuations in squirrel populations.
Like many diurnal animals western gray squirrels are secretive and cautious. When squirrels perceive danger, they retreat to dense foliage in tree tops. There they remain motionless and nearly invisible until the danger has passed.
Thanks to Dr. Stephen Cross for the loan of his thesis and his efforts to understand the biology of our native gray squirrel.
— Dr. Frank Lang