2019 Brandeis Bioliteracy Project's Journal

This week's Species of the Week is the eastern gray squirrel, or Sciurus carolinensis.
Native to the eastern half of the United States and southern Canada, the eastern gray squirrel can be found mainly inhabiting deciduous temperate forests, staying up high in tree branches in dens made of leaves, moss, and grasses. In these dens, they can live and raise their young, typically birthing 1-4 young per litter. However, they are also commonly found in human-settled areas, such as suburbs. Their range overlaps with the American red squirrel; however, these are not typically found in and around where people live. While typically gray in color with a lighter belly, eastern gray squirrels occasionally can be different morphs and have color changes in their coats. Melanistic individuals are completely black in color, and are often mistaken for being a separate species. Similarly, white individuals that have leucism (a genetic mutation similar to albinism) are uncommon but can be found; one leucistic eastern gray squirrel is a fairly common sight in the Boston Common.

Eastern gray squirrels eat a range of foods, including acorns, nuts, berries, tree bark, and some mushrooms. In addition, they also often use human-settled areas to their advantage by raiding birdfeeders for grains and seeds. Adults typically expect to live 5-10 years. Eastern gray squirrels are very commonly found around Brandeis University, and are a good introductory animal for iNaturalist.

Eastern White Pine or Pinus strobus, is an evergreen tree that can grow to about 230 feet and is a long-lived species with a life-span of around 200 years, sometimes as long as 450 years. Because of its thick bark, white pines are moderately fire resistant. Unfortunately, the Eastern white pine is vulnerable to the white pine weevil which is the cause of most of its destruction outside of human influence. White Pine is a fun tree to know about both because it occurs in our area and because it is pretty easy to identify; the needles occur in bundles of 5, which is easy to remember because there are 5 letters in the word white.


Other identifiers are their white stomata, identifiable as a white line on the underside of the needles, and the needles are usually about 3-5 inches. The cones of the white pine are about 3-6 inches long and are a light tan color, sometimes whitesh. This is a good species to keep an eye out for in and around campus as they are relatively easy to spot even in the snow or in the New England winter when many other species of plants are without leaves.

This week's species is Tsuga canadensis, otherwise known as the Eastern Hemlock. It is in the family Pinaceae (which is the same family as the Eastern White Pine), and can be found pretty much everywhere along the east coast of the United States and Canada. It is a coniferous tree , marked by its flat, single needles, which have white stripes along the underside. As a young tree, the bark will be greyish and smooth, but it will get scalier, more furrowed, and more red-brown in color as the tree ages.

Another identifier of the Eastern Hemlock is its cones, which tend to mature around early fall. They are round, and much smaller than those of the Eastern White Pine. One threat to the Eastern Hemlock is the Hemlock Wooly Adelgid, which is a pest that has decreased hemlock populations significantly. This has caused the Eastern Hemlock to be considered Near Threatened by the International Union for Conservation of Nature (IUCN) Red List.