Early-Summer Reproductive Curtailment in Wild White-Footed Mice and Reproductive Recovery in the Laboratory

Abstract

Reproduction is consistently and significantly (P ≤ 0.01) curtailed during May–July in wild populations of Peromyscus leucopus noveboracensis in eastern Virginia. To measure capability of reproductive function, wild mice were captured during the reproductive hiatus and at other times of the year and paired for 100 days in the laboratory with each other or with parous or nulliparous mice from my laboratory colony. Reproduction following pairing with laboratory mates was significantly more frequent (P ≤ 0.025) for wild males than for wild females, no matter when they were captured. Individuals captured during the reproductive hiatus and maintained as wild pairs rarely reproduced until re-paired with proven laboratory mates; in these trials, wild males reproduced significantly more frequently than wild females (P ≤ 0.01). The latency to reproduce was significantly (P ≤ 0.05) less for wild males captured other than during May, June, or July and paired with parous females compared to those paired with nulliparous females, no matter when they were captured. Reproductive suppression occurring in the wild is not permanent in the laboratory, particularly among males where 60% reproduced within 100 days after pairing. Reproductive performance of wild pairs prior to and following separation of males and females and pairing with proven mates suggests that female response is a key factor in the delay of reproduction in the laboratory, and perhaps, during the reproductive hiatus in the field.