Red Squirrel

Quick Take

• Red squirrels' brains physically change every fall, a transformation that is directly tied to their survival strategy. See foraging and caching →
• Some squirrels skip the hard work of foraging entirely, and their method turns out to be surprisingly calculated. Explore theft behavior →
• A mother squirrel can pass down property to her offspring, a behavior that dramatically changes their odds of survival. Maternal care and survival →
• The red squirrel's bushy tail does something most people would never guess. Discover the tail's function →

A type of rodent, the American red squirrel is an agile tree climber found almost anywhere with mixed hardwood and evergreen conifer forests. They’ve also adapted very well to urban and suburban environments. Renowned for their excellent memory, American red squirrels will bury their food for the winter and then return to it later to feed. While easily dismissed for their small size and ordinary appearance, they are actually quite remarkable creatures.

5 Incredible Red Squirrel Facts

• Red squirrels play an important environmental role by dispersing seeds and fungi throughout the ecosystem. After burying a cache of food, the squirrel sometimes forgets about it or fails to return, leaving the seed to germinate.
• One of the more amazing facts is that squirrels can remember the location of thousands of nuts they buried during their preparation for the lean winter months. Their brain even seems to expand in size and develop more neural activity during the fall.
• The squirrel’s big, bushy tail is not just for show. It helps to provide balance and regulate body temperature.
• Another amazing fact is that squirrels have a remarkable ability to jump vertically around 4 feet and horizontally around 6 to 8 feet. Like cats, they seem to land on their feet without any problem by twisting their bodies in the air and rotating their tail.
• There are 25 recognized subspecies of American red squirrels, each isolated by region.

Evolution

The earliest fossil evidence of squirrels was found in western North America and dated to around 36 million years ago. Six million years later, fossil records indicate that squirrels appeared in Europe. During that time, the Bering Strait land bridge provided passage for many different species — including squirrels — from North America. Squirrels appear in African fossil records shortly after Africa collided with Eurasia about 18 to 20 million years ago. After that, squirrels evolved and adapted to their diverse environments — into the over 200 species known today.

Classification and Scientific Name

The scientific name of the American red squirrel is Tamiasciurus hudsonicus. It was named after Hudson Bay, where it was first cataloged in 1771. Its closest living relatives in the genus Tamiasciurus are the Douglas squirrel and Mears’s squirrel, both of which have a more gray-brown body color. The American red squirrel should not be confused with the Eurasian red squirrel, which is a separate species in a different genus. There are 25 subspecies of American red squirrels.

Appearance

The red squirrel can be identified by its small but stout body, relatively large paws, bushy and curling tail, and erect ears with small tufts of fur. Their long incisors, which help them cut through tough material, can grow 6 inches in a year and must be worn down by eating and gnawing. The back and face are covered in a rusty red color that turns slightly gray in the winter, while the underside of the body and the ring around the eyes are white. There are also black parts around the tail and nose.

Red squirrels are roughly the size of a large book. They weigh between 7 and 10 ounces and measure about 10 to 15 inches with the tail included. Both males and females are similar in appearance.

Red Squirrel vs. Grey Squirrel

In North America, there are several species of grey squirrel, including the eastern grey squirrel, the western grey squirrel, the Arizona grey squirrel, and the Mexican grey squirrel, all of which belong to a separate genus, Sciurus. Besides the obvious differences in color, the red squirrel is about 30% to 50% smaller than other types of tree squirrels. It also has tufts of fur on the ears and lacks the multi-colored “halo” effect around the tail.

Behavior

The American red squirrel is a true expert at foraging for limited resources. The peak of their activity occurs in the fall when they prepare to stock up on food for the winter. The squirrel will bury thousands of different nuts every year in random underground caches around its territory. To find where it hid the food, the squirrel relies on its excellent memory. Some studies on a similar grey squirrel demonstrate that squirrels can still recall the solution to a puzzle two years after first learning it.

For a small number of squirrels, the arduous process of collecting nuts may be too much work. They will spy on other squirrels that bury their food and then resort to outright theft. This competition for food may be a matter of life and death since the winter can be harsh and unforgiving. As the temperature drops, the squirrel becomes progressively more lethargic and inactive. It does not quite enter a state of hibernation, however, since it will leave the nest to forage and eat at least once a day.

Red squirrels are highly territorial in nature and do not tolerate the presence of intruders. Each one maintains a territory a few acres in size. Their aggression tends to ramp up in the fall as they prepare for the mating season and the lean winter months. Squirrels will construct their nests somewhere within their territory and close to the food caches.

They prefer to inhabit the natural hollows and cavities of trees, but if these are not available, then they will usually build a nest in branches, underground burrows, and even human homes and buildings. They are very discriminating in their choice of homes. Tree diameter, the structure of the branch, and the existence of escape routes are all factored in. The nests will be lined with grasses, moss, feathers, leaves, and fur.

To communicate, the red squirrel produces a cacophony of chirping, growling, screeching, and buzzing sounds. Most of these sounds serve as a warning against predators, threats, or anything else that encroaches on its territory. The sounds also help aggressive males drive off reproductive competitors in the breeding season.

A scent marking is usually the first sign that a squirrel is intruding on another’s territory. This is usually enough to drive away intruders and prevent unnecessary conflicts. But if these incursions persist, then a fight may break out among the squirrels.

Habitat

The red squirrel can be found almost anywhere in Canada and the United States (including Alaska) with plenty of coniferous tree cover. This means it’s much less common in the Great Plains states, the southeastern US, and parts of the Pacific coast. It seems to prefer a habitat of mixed hardwood-conifer forests with spruce, pine, hemlock, or fir trees at elevations of up to 2,500 feet.

Predators and Threats

Many red squirrels die from predation and natural attrition each year, but this species does not face any significant threats in the wild. Habitat loss is generally not a problem on the whole. While squirrels may lose some territory to logging and development, the amount of tree cover has remained steady in the United States. Perhaps the biggest problem is that red squirrels are sometimes outcompeted for resources, especially by their larger and bulkier grey cousins.

What eats the red squirrel?

The red squirrel is preyed upon by weasels, martens, minks, foxes, lynxes, snakes, eagles, owls, and hawks. Humans have historically hunted them for food and for their fur.

Diet

What does the red squirrel eat?

The red squirrel primarily feeds on seeds and nuts. These highly opportunistic animals will supplement their diet with the occasional piece of fruit, mushrooms, tree sap, flowers, insects, or bird eggs. To draw out the tree sap, the squirrel punctures the sap-carrying vessels and harvests it later. But it will only resort to this if other food is not widely available. The green seeds of conifer trees appear to be the squirrel’s favorite type of food.

Reproduction and Life Cycle

The red squirrel has one or two defined breeding seasons per year, usually lasting between February and March and between June and July. Males compete against each other quite aggressively to acquire the most mates. Individual pair bonding is rare. The female may only be in estrus (meaning sexually available) for one day every breeding season. In this short window, the males will spend their energy pursuing the female and driving off other competitors.

After a pregnancy period lasting about a month, the female gives birth to an average of four (though as many as eight) young at a time. These baby pups are born completely helpless and without much fur. The mother assumes sole responsibility for raising the young, while the male usually returns to his own territory and has no further contact with the female or the offspring.

Lactation occurs for the first 70 days after birth. After each baby is weaned off the milk, the pups are expected to become fully independent. Sometimes, when the mother is ailing, the newly mature squirrels may receive portions of her territory, much like heirs to an estate. This will significantly increase their odds of survival.

Red squirrels have a very high birth rate, probably because they also experience a very high youth mortality rate due to predation, lack of food, and harsh environmental conditions. Only about a quarter of them will survive their first year of life. If they do grow out of the juvenile phase, however, they will have a lifespan of about five years. The oldest squirrel on record lived about 10 years in the wild.

Population

The American red squirrel is currently classified as a species of least concern by the IUCN Red List. While population numbers are not well-known, this species probably numbers in the millions. However, this obscures some variability in the population numbers of some local subspecies. The Mount Graham red squirrel of Arizona, for instance, is known to be endangered, with only a few hundred individuals remaining in the wild.