Latitude, life history and sexual size dimorphism correlate with reproductive seasonality in rodents

Abstract

Abstract Rodents show an immense variation in reproductive seasonality, spanning the whole spectrum from strictly seasonal to continuous reproduction throughout the year. However, the factors causing this variation have so far mostly been investigated in single‐species studies that could not address phylogenetic constraints. By applying both a categorical description and a quantitative measure, the present study characterises the degree of reproductive seasonality in the wild of 272 rodent species. Using a comparative approach, the relationships of 12 variables, comprising five life‐history variables, three abiotic variables, two niche variables and two allometric variables, with reproductive seasonality in rodents, were tested. The majority of rodents reproduced non‐seasonally and had particularly high intraspecific variation in reproductive seasonality compared to other mammalian groups. Their opportunistic breeding strategies, their large geographic ranges with wide latitude and elevation ranges, and their ability to live in human‐made environments may be related to this broad intraspecific variation of birth season length in rodents. The most important variables associated with rodent reproductive seasonality were mid‐latitude of the species’ geographical range, temperature, litters per year, weaning age, age at sexual maturity and sexual size dimorphism. Birth seasons become shorter with increasing latitude and colder temperatures, corresponding to the decreasing length of the favourable season. Species with more pronounced birth seasonality have fewer litters, which are weaned earlier and reach sexual maturity later, corresponding to the shorter period of optimal environmental conditions for reproduction. Sexual size dimorphism was weakly associated with birth seasonality, with more seasonal species having a higher degree of male‐biased sexual dimorphism, potentially because male–male competition and female monopolisation are more likely to evolve in species with short mating seasons. In conclusion, habitat seasonality and life‐history adaptations are most strongly associated with reproductive seasonality in rodents, which has important implications for zoo husbandry and for the effects of climate change on rodents.