Here we are in the dead of winter with nighttime temperatures falling into single digits, and despite this I am seeing signs that the breeding season for wildlife has begun.

On Jan. 15, Mary Alice and I watched three squirrels chasing each other. These wild chases are a sure sign that winter mating activity has begun for gray squirrels. The males chase females that are coming into estrus. The gymnastics of these chases are spectacular as the squirrels run up and around the tree trunks, running out on limbs and jumping from one tree to another at top speed, with a lot of chattering occurring.

Usually, these chases are joined by two or even three more males. Not only is the male trying to catch the female, he is also chasing other males away. I thought these breeding chases were happening earlier than previous years so I checked through diaries and found that the squirrels are right on schedule.

I remember watching one of these squirrel chases, in which I assumed a male was chasing a female; however, two other squirrels joined in the chase. The first squirrel broke off the chase of the female and immediately attacked the two newcomers in an effort to chase them away.

The four squirrels scurrying through the treetop created quite a show. After much calling and chasing, the dominant male won and the two rival competitors left.

With the competitors gone, the male again turned his attention to the female, who after climbing high into a treetop, was lying flat on a limb. As the male approached she did not run away. I could hear soft murmurings being exchanged. The male had his frosted tail on full display. It was curved forward and tilted to one side as he positioned himself so that the female would have a full view of him. Later, I read this was similar to the male turkey who fans his tail to attract a hen.

After a gestation period of 44 days, the female will give birth to a litter of four or five. The female is a very good mother. She will nurse the young for five to seven weeks. Some female gray squirrels will give birth to a second litter in July or August. There have been cases of grays bearing three litters in one year; however, this is extremely rare.

Winter breeding depends heavily on the quality and quantity of food available during the fall and the condition of the squirrels as they enter the winter months. This is nature’s answer to birth control. Poor food conditions in the fall will lead to fewer litters in the spring.

At birth, a gray squirrel will only weigh one half of an ounce and measure approximately four and one half inches in length. By the end of the first week, the squirrel will weigh more than an ounce and have grown to three-fourths of an inch. At two weeks, the back is darkened by the first hair growth. During the last half of the third week, the ears open, and the lower incisor teeth erupt from the gums.

During the fourth week, silver hair appears on the tail, and the body will be entirely covered with hair. In the fifth week, the eyes open, the upper incisors appear and the young will be ten inches long. At this time, the young squirrels will venture from the tree and climb onto the ground for the first time.

The female gray squirrel keeps a very clean nursery. Nestling gray squirrels will set up distinct areas for defecation, with the practice of urinating in one site strongly developed. Even though the den has not been disturbed the mother commonly moves the nestlings.

To move a nestling, a mother squirrel grasps the belly skin in her teeth, and the nestling clutches the mother’s head and neck with all four paws. A very young squirrel might be grasped by the middle of the body.

Due to the mother’s care, survival of the young squirrels is amazingly high, with very few, if any, of the young dying before they leave the nursery den. Even after young squirrels leave the nest their mother watches over them to some extent, giving warnings of low-pitched calls from the den tree. Juvenile squirrels have been observed hurrying to a den tree after hearing these maternal signals.

One study done in April of 1960 stated that at times, the juveniles will stay home until the next brood is about to arrive and could even be left in possession of their home den while the mother finds a new maternity den. However, if den sites are scarce, the older litter is usually evicted before the arrival of the new brood. The youngsters often move miles before settling down to their adult roles.

Compared to most small mammals, the squirrel leads a remarkably long life. In the wild, gray squirrels can live two to three years, and in captivity, they can live up to ten years.

Because a squirrel’s front teeth never stop growing, the squirrel is constantly chewing on hard materials, such as dead animal bones, tree bark, etc. The teeth also wear on the opposing teeth. In some cases, when one incisor is damaged the other tooth keeps growing, sometimes curving out of the mouth and over the top of the head or under the lower jaw. This is known as malocclusion.

Stub-tails are common among squirrels, most likely caused by fighting rather than predation. Usually, such deformities won’t hamper the squirrel’s climbing and leaping abilities; although, it has been claimed that the squirrel’s tail is a vital part of his balancing equipment.

The gray squirrel’s scientific name is Sciurus caroliniensis, which is derived from two Greek words: skia, meaning shadow or shade and oura, meaning tail. Thus, the squirrel is the one who sits in the shadow of his tail. The origin of the English word squirrel lies in the Greek word skiouros.

Bill Bower is a retired Pennsylvania Game Commission Wildlife Officer. Read his blog and listen to his podcasts on the outdoors at www.onemaningreen.com.