Sex- and cohort-specific life-history strategies in Mongolian gerbils (Meriones unguiculatus)

Abstract Information on life-history traits is crucial for understanding rodent evolution, ecology, and behavioral strategies. Here, we report on the results from a 4-year study that collected data on the sexual and seasonal cohort (winter C 1, spring C 2 , and summer C 3 ) life-history traits of Mongolian gerbils ( Meriones unguiculatus ) maintained in a natural enclosure, using monthly live trapping, in Inner Mongolia (China). We found no sexual differences in the observed longevity, age of maturity, potential reproductive life span, or dispersal in the year of their birth, apart from a male-biased dispersal after gerbils overwintered as adults. Nevertheless, we did find cohort-specific life-history patterns in the above traits; for example, the C 1 females matured at a significantly earlier age than did the C 2 and C 3 females, while the C 3 gerbils commonly delayed their reproduction to the following year. Moreover, 21.7% of C 1 and 6.1% of C 2 females bred more than one litter, yet none of the C 3 females did so during their birth-year breeding season. The average number of litters per female of C 1 was greater than that of either C 2 or C 3 in their birth-year breeding season. Our results suggest that sex-specific life history traits may align with the predictions of sexual selection and the monogamy system hypothesis in Mongolian gerbils. In addition, the seasonal cohort-specific life-history traits revealed here lend support to the hypothesis of an adaptive switching behavior—from fast to slow development in the later-born gerbils—as opposed to the hypothesis of direct environmental limitation, although the slight inter-annual variation detected is consistent with the precipitation constraints.