Why does a rat bite its pups? - briefly
Maternal rats may nuzzle or chew newborns to remove membranes, stimulate breathing, or eliminate weak offspring, thereby enhancing the survival of the stronger litter. Excessive aggression often signals stress, overcrowding, or inadequate nutrition, prompting the mother to cull pups she perceives as unlikely to thrive.
Why does a rat bite its pups? - in detail
Maternal aggression in rodents often manifests as biting of newborns. This behavior serves several adaptive functions.
The mother may eliminate weak or malformed offspring to allocate resources to viable pups. When food is scarce, competition intensifies and the mother reduces litter size by killing the least fit individuals. Hormonal fluctuations after parturition also influence aggression; elevated prolactin and oxytocin levels can trigger protective but sometimes hostile actions toward the young.
Stressors unrelated to nutrition can provoke lethal handling. Overcrowding, excessive handling by humans, or disturbances in the nest environment increase cortisol, which correlates with higher rates of pup‑directed biting. Illness or injury in the dam may impair maternal instincts, leading to neglect or aggression.
Genetic predisposition plays a role. Certain laboratory strains display higher frequencies of infanticidal behavior, suggesting inherited components. Early exposure to predator cues or aggressive conspecifics can condition the mother to respond violently toward her own litter.
Environmental conditions influence the likelihood of this conduct:
- Temperature extremes that destabilize nest warmth
- Poor bedding that compromises nest integrity
- Presence of unfamiliar scents or chemicals
Each factor can disrupt the delicate balance of maternal care, prompting the mother to bite her offspring as a maladaptive response to perceived threats or resource limitations.