ABSTRACT
Huddling with other individuals is an effective way to reduce heat loss. This cooperative behavior requires that the individuals tolerate each other's presence at least for a certain time or under certain circumstances. In our study, we investigated the effects of ambient temperature and familiarity on the huddling behavior of two closely related mouse species, the mound-building mouse (Mus spicilegus) and the house mouse (Mus musculus musculus). While their geographic distribution overlaps, their social systems differ in many aspects. Whereas house mice are territorial, mound-building mice tolerate each other and live in groups during winter. In laboratory experiments we found that familiarity and ambient temperature influenced the huddling behavior of both species. Familiar individuals were more likely to huddle, but while mound-building mice did so at all temperatures, huddling in house mice increased with lower temperatures. Our results are consistent with the previous knowledge about these species' social systems and might provide us with more details about their sociality. Investigating huddling behavior might be a good way to measure social tolerance between individuals within a species and compare social systems of different species.
Subject(s)
Behavior, Animal/physiology , Mice/physiology , Recognition, Psychology/physiology , Social Behavior , Temperature , Territoriality , AnimalsABSTRACT
The Trivers - Willard hypothesis (1973) suggests that the maternal condition may affect the female's litter size and sex ratio. Since then other factors had been found. Previous findings revealed in the case of some mammalian species, that females with larger anogenital distance have smaller litters, while the sex ratio is male-biased. That has only been demonstrated in laboratory animals, while the genetic diversity of a wild population could mask the phenomenon seen in laboratory colonies. We examined the connection between morphological traits (weight and anogenital distance) and the reproductive capacity of two wild mice species, the house mouse and the mound-building mice. We showed in both species that anogenital distance and body weight correlated positively in pre-pubertal females, but not in adults. Neither the house mouse nor the mound-building mouse mothers' weight had effect on their litter's size and sex ratio. Otherwise connection was found between the mothers' anogenital distance and their litters' sex ratio in both species. The results revealed that females with larger anogenital distance delivered male biased litter in both species. The bias occurred as while the number of female pups remained the same; mothers with large anogenital distance delivered more male pups compared to the mothers with small anogenital distance. We concluded that a female's prenatal life affects her reproductive success more than previously anticipated.
Subject(s)
Sex Characteristics , Sex Ratio , Age Factors , Animals , Animals, Newborn , Body Weight , Female , Litter Size , Male , Mice , Sex Factors , Sexual MaturationABSTRACT
The house mouse (Mus musculus) and the mound-building mouse (M. spicilegus) differ in their mating and social systems. The M. musculus is polygynous and females tend to breed cooperatively while M. spicilegus is known to be monogamous and famous for its unique cooperative behavior; the communal overwintering. Mus spicilegus is considered as a highly aggressive species in the genus Mus. In the present study, we attempted to analyze the development of aggressive and sociable behavior in these species and to discover how familiarity with the target moderates the development of sociable and aggressive behaviors and moderates the differences between the species. Dyadic social interaction tests in neutral cages were performed on 21-, 60-, and 120-day-old mice of both genders and both species. Each individual was tested against a sibling and an unfamiliar individual at all three ages. Our results showed that the development of aggressive and sociable behavior with age differed between the species and sexes; however, familiarity with the other mouse moderated the effect of species on aggression. At 21 days, both genders of M. spicilegus were more aggressive against strangers than siblings. This became true of both species at 60 days. When facing a stranger, both sexes of M. spicilegus were more aggressive than M. musculus at 120 days. However, when facing a sibling, neither gender of M. spicilegus was more agonistic than M. musculus, indicating that either kinship or early social experiences elicit tolerance.
