The arrival of newborn rats, often called pups, marks the beginning of a period of rapid transformation. Born in an undeveloped state, these tiny creatures undergo profound changes in appearance, abilities, and independence. Their survival and development are linked to the care provided by their mother.
Initial Appearance and Vulnerability
Newborn rats are born in an altricial state, highly underdeveloped at birth. They weigh 6 to 8 grams, comparable to the weight of a nickel. Their eyes and ear canals are sealed, rendering them blind and deaf. Their skin is bright pink and translucent, lacking fur, which makes them susceptible to heat loss and hypothermia.
Without coordinated movement, they cannot acquire food or regulate their own body temperature, making them entirely dependent on their mother for survival. This helplessness highlights their vulnerability during the initial days of life.
The Mother’s Role in Early Life
The mother rat, or doe, plays a comprehensive role in the survival and early development of her pups. She instinctively builds a nest, often piling materials to create a sheltered, dark space with a single entrance. This nest provides a safe and warm environment for the newborns.
After birth, the mother meticulously cleans each pup, removing the birth sac and ingesting the placenta, a practice known as placentophagy. She retrieves any pups that wander or are dragged from the nest, carrying them gently by the nape of the neck back to the warmth and safety of the litter.
Nursing is a constant activity in the first week, with pups suckling for up to 18 hours daily. The mother also performs various licking behaviors, including anogenital licking, which is necessary to stimulate urination and defecation in the pups, as they cannot perform these functions independently. Maintaining warmth is also a shared responsibility, with the mother huddling over her litter to provide body heat.
Key Developmental Stages
The developmental timeline of rat pups is fast, with milestones occurring within weeks. By day 6, a light peach fuzz of hair appears, and by day 9, their coats are noticeable. Around day 10, the ears separate from the head, and ear canals open around day 12, allowing full hearing.
Eye-opening occurs around 14 days of age, after which pups become more active and begin to explore their immediate surroundings. Initially, their movement is a squirming motion, but by day 10, they start to crawl, progressing to unsteady walking around day 12. As they approach three weeks of age, they begin to nibble on solid foods, though they still rely on their mother’s milk. Weaning, the transition to entirely solid food, is completed by four weeks of age. By six weeks, they are well-developed.