The mother mouse, often called a dam, displays dedication to her offspring, playing a central role in their survival and early development. Her life cycle revolves around a prolific reproductive capacity, enabling rapid population growth. The behaviors she exhibits, from nest construction to pup rearing and protection, ensure the continuation of her lineage.
Pregnancy and Nesting
A female mouse’s journey to motherhood begins with a gestation period lasting between 19 and 21 days. This short pregnancy allows for frequent litters, sometimes 5 to 10 per year, with an average of 6 to 8 pups per litter. As birth approaches, the pregnant mouse instinctively builds a secure nest.
She gathers soft materials like shredded paper, fabric scraps, cotton, grass, and twigs to construct a warm, concealed, and safe environment. The nest is dome-shaped and multi-layered, providing insulation and protection from the elements and threats. It offers the helpless newborns the warmth and security they need.
Caring for Newborn Pups
Newborn mice are born in an altricial state, entirely dependent on their mother for survival. They are hairless, with sealed eyes and ears, and possess limited sensory and motor skills. Immediately after birth, the dam begins care.
She nurses her pups, providing them with milk. The mother also frequently licks her pups, which stimulates their bodily functions and keeps them clean. If any pup strays from the nest, she retrieves it gently, carrying it back to the warmth and safety of the group. Her body heat is important, as the pups cannot regulate their own temperature during their first weeks of life.
Pup Development and Weaning
The initial weeks of a mouse pup’s life are marked by rapid development under the mother’s care. Hair begins to appear around day 2 to 4, and fur fully develops by day 10, giving them a fuzzy appearance. Their ears open between day 3 and 5, allowing them to perceive sounds.
Around day 13 to 14, their eyes open, enabling them to explore within the nest. By 16 days of age, pups may start nibbling on solid food, although nursing continues. The weaning process, where pups transition from milk to solid food, completes when they are about 3 to 4 weeks old, after which they become more independent.
Protective Instincts and Challenges
The mother mouse exhibits protective instincts to safeguard her litter, which can include aggressive behavior towards perceived threats. She uses olfactory cues from her milk and urine to establish a unique social identity for her litter, and disruptions to these scents, such as from human handling, can disturb her maternal behavior.
In challenging situations, a mother mouse may exhibit culling or infanticide, where she removes or consumes some of her pups. This is not an act of malice but a survival response to factors like insufficient milk production, malnutrition, or an overcrowded environment. By reducing the litter size, she ensures the remaining pups have a greater chance of survival and access to limited resources. This behavior can also occur if pups are sick or deformed, to maintain the litter’s health.