Seasonality of reproduction in Bathyergidae is a function of group size: A novel hypothesis (Rodentia)

Abstract

In the African mole-rat family (Bathyergidae), species show both year-round and seasonal breeding patterns even though all species inhabit regions with varying seasonal rainfall patterns (a well-known selection driver of seasonal breeding). This short review suggests a novel hypothesis explaining why some African mole-rat species breed seasonally and others year-round. Namely, group-living African mole-rat species (with a mean colony size greater than five) exhibit an aseasonal reproduction pattern, as breeders, particularly females, possess year-round high body conditions. This is likely due to access to abundant and high-quality resources (food and water) throughout the year and reduced frequency of engaging in strenuous activities, such as digging, due to the increased efficiency of locating and retrieval of resource as a function of group size. While in the solitary and social species, with mean colony sizes of five or less, there are too few colony members to provide sufficient cooperative care benefits, the breeders show a seasonality to their body condition and thus breeding investment. As such, we hope to start a discussion on how group size could affect circannual breeding rhythms and propose some avenues for future research.