Polar Bear Maternal Care, Neonatal Development, and Social Behavior

Abstract

AbstractPolar bear maternal behavior and neonatal development are difficult to study because maternal dens are secluded and generally inaccessible. As a result, much of what we know comes from polar bears in zoos. Altricial polar bear cubs (litter size 1–3) have limited sensory capacity, sparse fur, and are completely dependent on the female for nourishment, warmth, and protection. Energy for the female’s metabolic requirements and milk production comes from body fat during the 12-week denning period. Because females fast and lactate while caring for neonatal cubs, they lose ~44% of their body mass during the denning period. Maternal attentiveness to cubs accounts for <15% of the daily activity budget in the den and includes nursing, licking, positioning cubs, and postural changes to ensure cubs stay warm. The female shelters the cubs on her chest, covering them with her limbs to provide thermal insulation and warmth while affording proximity to teats for nursing. With a fat content of ~36%, milk provides the energy and nutrients needed for rapid maturation. Polar bear cubs vocalize ~25% of the time, usually associated with nursing while in the den. When cubs emerge from the den after 12 weeks, they have a litter mass that is similar to the gestational mass of other similarly sized mammals for the same period. Cubs nurse for up to 2 years, although they also eat seals captured by the female. Polar bears have a highly developed olfactory capacity, and exposure to sibling and maternal scent may reinforce kin recognition. Generally solitary, polar bears demonstrate social flexibility. Social interactions outside of reproductive contexts are largely associated with concentrated resources, such as food or habitat, and there is a range of characteristic social interactions in these settings, from adult social play to aggression, tolerance, and avoidance. Climate change and the loss of sea ice will affect polar bear social interactions, pre-denning energy storage, the timing of denning and parturition, maternal behavior, and cub survival.KeywordsAcousticAltricialBehaviorDenCommunicationGestationLactationMaternalNeonatalOlfactoryParturitionPolar bearSensorySocialThermoregulationVocalization