Determining a squirrel’s age can be helpful for various reasons, from assisting in wildlife rescue efforts to understanding these common backyard creatures. While squirrels do not come with obvious age markers, observing their physical development and behavior provides reliable clues for assessing their life stage.
Understanding Squirrel Life Stages
Squirrels progress through distinct life stages: infancy, juvenility, and adulthood. Each phase is characterized by different levels of dependence and physical development. Newborn squirrels, or neonates, are entirely reliant on their mother. As they grow, they transition into the juvenile stage, where they begin to explore and learn essential survival skills. Finally, they reach adulthood, becoming fully independent and capable of reproduction.
Physical Clues to Age
Observable physical characteristics offer insights into a squirrel’s age. At birth, neonates are hairless and pink, resembling tiny pink erasers, with their eyes and ears closed. They weigh around 10-20 grams and are about the size of a human thumb.
Around one to two weeks old, their skin shows a grayish tint as fur starts to grow, remaining sparse. By three weeks, a fuzzy fur layer becomes noticeable, and their ears begin to open, allowing them to hear. The lower front teeth also start to emerge.
Between four and five weeks, their eyes open. At this point, their fur is more developed, and the tail starts to show some hair, though not yet bushy. Their body size increases, and they can weigh between 30-100 grams. The upper front teeth also emerge by five weeks.
By six to seven weeks, the squirrel is fully covered in fur, and its tail begins to appear fluffier. They also develop their first set of cheek teeth around this age, which are important for processing solid foods. At eight weeks, they closely resemble miniature adults, with full fur and bushy tails. Their weight can reach around 100 grams by eight weeks and up to 200 grams by ten weeks. As squirrels age into adulthood, their continuously growing incisors show more wear patterns from gnawing, with older squirrels having shorter and more rounded teeth.
Behavioral Indicators
Behavioral patterns also provide clues about a squirrel’s age and developmental stage. Newborn squirrels are completely immobile, relying entirely on their mother for warmth and feeding. By three to four weeks, their mobility increases from slight movements to stronger crawling, though they remain wobbly. As they approach five weeks, they can grasp objects but still lack fine motor skills.
Around six to seven weeks, they begin to sit up and become more active, exploring their immediate surroundings. At this stage, they transition from solely nursing to nibbling on solid foods like fruits and nuts, although milk remains a primary food source.
By eight weeks, juvenile squirrels start venturing outside the nest, with tentative explorations guided by their mother. They develop climbing abilities and learn to forage independently, mimicking adult behaviors. While still learning, they exhibit increased playfulness and curiosity. Squirrels are typically weaned around eight weeks but may stay with their mother until 10-12 weeks. A squirrel that is old enough to run from a human is generally considered independent.
Estimating Age and Its Limitations
Estimating a squirrel’s age involves combining observations of its physical traits and behaviors. For instance, a hairless squirrel with closed eyes is a neonate, while one with fully opened eyes and a bushy tail is likely a juvenile approaching independence or an adult. Weight can also be a helpful indicator, with younger squirrels being significantly lighter.
However, precise age determination is challenging without specialized techniques. Environmental factors, like nutrition, can influence development, leading to variations in the rate at which physical and behavioral milestones are met. Therefore, the methods described provide an estimation rather than a definitive age. If you encounter a squirrel that appears orphaned, injured, or in distress, especially if it approaches humans or seems disoriented, contacting a licensed wildlife rehabilitator is advisable. These professionals possess the expertise and resources to assess the animal’s needs and provide appropriate care.