The fox squirrel (Sciurus niger) is the largest species of tree squirrel native to North America. Its robust build makes it noticeably larger than other common squirrels across its wide range. This article details the fox squirrel’s physical measurements, explains how its size changes based on location, and compares it to the Eastern Gray Squirrel.
Core Physical Measurements
Adult fox squirrels typically measure between 18 and 29 inches in total body length, including the head, body, and tail. Their weight generally falls between 1 and 3 pounds, contributing to their heavy-bodied appearance.
The characteristic long, bushy tail is a major component of its overall length. The tail alone can measure from 8 up to 15 inches, frequently making up nearly half of the animal’s total dimension. This proportional length is a helpful identifier, though the tail is often less thick than that of its gray squirrel relatives.
Geographic Differences in Size
Fox squirrel size is not uniform across the entire range, with variations linked to geography and resource availability. This difference is an example of clinal variation, where physical traits change gradually across a species’ distribution. Individuals found toward the western edge of the range tend to be smaller.
Conversely, some subspecies found in specific regions are known for their exceptional size. The Delmarva Peninsula fox squirrel (Sciurus niger cinereus) is a notable example, with some individuals reaching lengths of up to 30 inches and weights near 3 pounds. Environmental factors, such as the local abundance of mature forests providing a reliable supply of acorns and other food sources, can influence the maximum size an individual population achieves. This means that the biggest fox squirrels are often found where food is plentiful and consistent.
Size Comparison to the Eastern Gray Squirrel
To visualize the fox squirrel’s size, it is helpful to compare it to the Eastern Gray Squirrel (Sciurus carolinensis), which is more commonly seen in many urban and suburban areas. The gray squirrel is considerably smaller, typically reaching a maximum total length of about 21 inches. Gray squirrels are also much lighter, weighing between 0.75 and 1.5 pounds on average.
The fox squirrel is frequently described as being one and a half to two times the size of its gray cousin, appearing noticeably stockier and more robust. In terms of mass, the fox squirrel is usually 25% to 50% heavier, and in extreme cases, the weight of a single large fox squirrel can equal that of three smaller gray squirrels. This difference in size makes the fox squirrel appear bulkier and less slender than the more agile gray squirrel.