Genetic Evidence for Long-Term Monogamy in a Small Rodent, Peromyscus polionotus

Abstract

Populations of Peromyscus polionotus, the oldfield mouse, are organized into family groups which are characterized by a high degree of monogamy. There is no evidence that females of this species ever mate with more than one male for each litter. Females that are collected in the field with males have the same mate for consecutive litters (the frequency of mate switching for these females does not differ significantly from zero). In addition, the male that is collected with the female is usually the father of her offspring (the frequency of nonpaternity is .117). Thus, oldfield mice are overwhelmingly monogamous. However, a few females may not form long-term monogamous relationships, as shown by the relatively high frequency of mate switching for females collected without males (.40). Recent research has uncovered several other probable cases of monogamy among small rodents. Any generalization about mating systems among mammals must consider the diversity of mating systems among small rodents. The methods used in this paper have generality and could be used to study the mating system in other mammals that are difficult or impossible to study by direct observation.