INFLUENCE OF MATING ON DURATION OF ESTRUS IN CAPTIVE WHITE-TAILED DEER

Duration of estrus may exceed 24 h in white-tailed deer (Odocoileus vi rginianus). We examined the influence of mating and injected gonadotro phin releasing hormone (GnRH; 100 mu g/deer) on duration of estrus. Ni ne adult females were monitored daily for estrous behavior during autu mn and winter 1991-1992 (31 separate estrous cycles). Estrus was asses sed using a tractable, epididyectomized adult male. From 13 November 1 991 to 3 January 1992 (experiment 1), adult females in estrus were ass igned randomly as either control (unbred) or bred to the epididyectomi zed male. In experiment 2, duration of estrus for females injected wit h GnRH was compared with unbred females from 2 February 1992 to 23 Mar ch 1992. For experiment 1, unbred females were in estrus longer (P = 0 .01) than were females that were bred ((X) over bar +/- SE; 2.3 +/- 0. 3 days versus 1.3 +/- 0.2 days, respectively). For experiment 2, durat ion of estrus for unbred females treated with GnRH did not differ (P = 0.48) from those that were not bred (1.7 +/- 0.3 versus 2.0 +/- 0.3 d ays, respectively). There was no significant (P = 0.71) change in the duration of estrus for unbred females between the two experiments. Cop ulation may shorten the duration of behavioral estrus. Administration of exogenous GnRH did not shorten duration of estrus. Prolonged durati on of estrus for unbred females may be a mechanism to help ensure all females are bred even in populations with low numbers of males.