The word "squirrel" comes from the Greek "sciurus," meaning "shadow tail," and refers to the bushy appendage possessed by most all squirrel species. They are members of the rodent family, and Texas is home to 10 species of squirrels, with four of them present in the Austin area.
Along with their bushy tails, squirrels are generally slender animals with large eyes and soft fur. Their front limbs are shorter than their hind limbs, with 4 or 5 toes on each foot. Their front feet include a usually underdeveloped thumb, and all toes have sharp claws for climbing trees and quickly clamoring over uneven terrain. Squirrels are strongly vegetarian and feed mostly on a wide variety of seeds, nuts, fruits, buds, bark, and leaves. Their vision is sharp, and they have "vibrissae" or specialized hairs on their head and limbs, which afford them an excellent sense of touch.
The most common tree squirrels in Central Texas are the Eastern fox squirrel (Sciurus niger) and the Eastern gray squirrel (Sciurus carolinensis). A large squirrel with rusty or reddish underparts and grayish or brownish upperparts, the Eastern fox squirrel prefers open woodlands of mixed trees and areas along rivers and streams, and makes its dens in hollow trees or nests made of leaves. Their diet is largely made up of acorns, which they bury in winter and relocate through their keen sense of smell. Mating occurs in January and February, and again in May and June, with offspring born in March and July.
The Eastern gray squirrel is a medium-sized squirrel with grayish upperparts with white-tipped hairs, white underparts, and a white spot at the base of their ears in winter. Not as numerous as fox squirrels, gray squirrels live in dense live oak stands and bottomland areas, with the Austin area in the westernmost part of their range. There are usually two openings to their nests, which are otherwise similar to fox squirrels, as is their diet and breeding cycle. Destruction of bottomland habitat from logging, overgrazing and development are the main reasons why gray squirrels are only locally common, and declining in many areas.
Our most frequently encountered ground squirrels include the rock squirrel (Spermophilus variegatus) and the Mexican ground squirrel (Spermophilus mexicanus). A rather large, stout squirrel with a blackish head and upper back and a mottled grayish-brown rump and tail, the rock squirrel is nearly always found in rocky canyons, cliffs, and rock piles, where they make their dens. While they can climb trees, they prefer to be ground dwellers, where they forage for acorns, nuts, insects and berries. In Central Texas, these squirrels hibernate beginning in November and emerge in late February or March to begin breeding.
The western edge of Austin is the easternmost range for the Mexican ground squirrel, a rather small squirrel with typically nine rows of squarish white spots on their backs and moderately bushy tails. They prefer brushy or grassy areas, including mowed lawns, golf courses, and parks, and live in burrows dug into the soil. As such, they are often considered pests and efforts are frequently made by humans to remove them. They eat chiefly green vegetation and insects, but are one of the few squirrel species that will eat meat, either in the form of small roadkill or even a member of their own species. Breeding begins in late March or early April, with a brood chamber built into a side tunnel in the deepest part of their burrow.
Anyone who has watched a squirrel running along a tree limb or across an open road with its bushy tail undulating and waving behind it, or spotted a squirrel sitting with its tail curled over its back while it eats or surveys its surroundings, can certainly appreciate why their name means "shadow tail."
As in several other cities in the U.S., Austin has a small population of ‘white squirrels,' found mostly in and around the University of Texas campus and surrounding neighborhoods. Contrary to popular belief, these squirrels are not albinos, but rare color variations of the Eastern Fox Squirrel, with a naturally occurring condition called ‘leucism.' Unlike albinism, this condition is caused by a reduction in all types of skin pigments, not just melanin. This is why these squirrels often appear pale yellow with normally colored eyes, instead of pure white with red eyes typical of an albino form. According to local legend, seeing a ‘white squirrel' is guaranteed to bring you good luck!
About Nature Watch
Nature Watch is a monthly feature in Venture Out by Lynne Weber and Jim Weber, the authors of "Nature Watch Austin: Guide to the Seasons in an Urban Wildland," recently published by Texas A&M University Press. They work in the Austin high-tech industry, where she is a senior manager and he is a senior engineer. Both are certified Texas Master Naturalists, and Lynne is past president of the Capital Area chapter. The Webers are dedicated naturalists who conduct bird surveys, monitor and map invasive species, write nature columns for neighborhood newsletters, and lead nature hikes among their many outdoor activities. Send your nature-related questions to firstname.lastname@example.org, and they will do their best to answer them.