Allomothering, allomatural infant care/handling, or non-maternal infant care/handling is alloparenting performed by any group member other than the mother or genetic father and thus is distinguished from parental care. It is a widespread phenomenon among mammals and birds. Allomothering comprises a wide variety of behaviours including: carrying, provisioning, grooming, touching, nursing, and protecting infants from predators or conspecifics. Depending on age-sex composition of groups alloparents, helpers or "handlers" can be non-reproductive males in polyandrous systems, reproductive or non-reproductive adult females, young or older juveniles, or older brothers or sisters helping to raise their younger siblings.
Non-Human Primates
Allomothering is particularly common among the Primate order. Vervets, cebus monkeys, squirrel monkeys, and macaques are all known for allomothering performed by females not closely related to the parents. These alloparents help by carrying the infant, providing food, and guarding the infant from predators. Cebus monkey females have been known to regularly nurse infants who are not their own. In these species allonursing is performed by related and unrelated females. Moreover, about 10% of nursing bouts are attributed to allonursing. Allomothering can also be performed by non-reproductive helpers like in the callitrichids. In the Callitrichids, allomothering care goes beyond many other species and infants are spontaneously provisioned by all group members without a prior begging call on part of the infants. These species practice facultativecooperative breeding, where a single dominant female reproduces and other group members provide the majority of care to the infants.
Proposed explanations
Older siblings promoting their own genetic material via helping their younger siblings are explained by the Theory of Inclusive Fitness: Offspring of the same parents are, on average, genetically equally close to their siblings as they would be to their own progeny. A number of adaptive functions have been proposed to account for the widespread incidences of allomaternal care in mammalian and avian species. Jane Lancaster noted the reproductive benefits for primates as k-strategists in learning to be better mothers, or acquiring mothering skills. Her learning-to-mother hypothesis postulates that primate females with no children of their own participate in allomothering, and evidence from studies by Sarah Hrdy and Lynn Fairbanks shows that: The hypothesis is supported by evidence of the success of allomothering as a learning technique: Other hypothesis include "alliance-formation", where subordinate allomothers endeavour to form social alliances with dominant mothers by interacting with their infants. Under kin-selection theory, related allomothers may improve their inclusive fitness if the allomothering behaviour contributes to the survival or faster reproductive rate of the mother. Finally, allomaternal care has been suggested to be a by-product of maternal care. However, this hypothesis would not explain the high levels of care seen by juvenile, subadult or unrelated adult males in many species. An infant's birthmother, in a climate of allomothering, may gain time relieved from parental duties, allowing her to forage more efficiently or reproduce more quickly. In some cases it may also improve the chances for her infant to be adopted by another resident female should she die. Infants may also benefit through a faster maturation rate or earlier weaning time. They may also gain valuable social skills by interacting with alloparents. Finally, infants may form social-alliances of their own and improve their chances of having future dispersal partners.
Malicious behavior
Allomothering care may not always be beneficial. In some cases "aunting-to-death" has been reported, where females withhold an infant from their mother until the infant dies, which can be explained either as incompetence or as competition in favor of the aunts' own offspring. In other cases infants may be kidnapped and receive life-threatening bites or hits from a supposed-alloparent. Mothers often restrict others' attempts to touch or handle their infants in species where the risk of injury or death is high.
