REARING RODENT PUPS IN FOSTER FAMILIES OF TNEIR OWN OR ANOTHER MAMMAL SPECIES: SURVIVAL AND THE CAUSES OF MORTALITY

Abstract

Conditions of rearing pups at an early age render a significant impact on subsequent development, reproduction and certain features of the behavior of mammals including rodents. Parents, mostly lactating females, are the main component of the social environment of pups at the early period of postnatal ontogenesis in most mammal species. Therefore, rearing pups in foster families of their own (in-fostering) or another, even taxonomically distant species (cross-fostering) is one of the main methods of assessing the impact of early experience and maternal environment on the development of animal behavior. Cross-fostering or in-fostering is also used for the conservation of valuable animal species. Therefore, more effective fostering methods that provide the maximum survival of the young are necessary to be developed. According to this, we investigated the survival and possible causes of the mortality of rodent pups representing several species in foster families of their own or another mammal species. We conducted a series of experiments on the cross-fostering and in-fostering of house (Mus musculus) and mound-building (Mus spicilegus) mice, yellow steppe lemmings (Eolagurus luteus) and brown rats (Rattus norvegicus), and on rearing rat pups in foster families of the European polecat (Mustela putorius). The proportion of successfully cross-fostered pups (0–68.4) was lower compared to the in-fostered (93.3–100) ones. This result is presumably explained by more significant differences in the maternal environment when reared by a heterospecific female. According to the literature data, the age of foster and recipient female pups, species-specific differences of odor, the presence or absence of a male and the level of paternal care, the level of stress of the mother and offspring, the expression of maternal instinct, the previous female experience in rearing its own and foster pups, the duration of lactation and the nutritional value of maternal milk are the factors that seem to affect the survival and mortality of foster pups.