Effects of male-biased harvest on mule deer: Implications for rates of pregnancy, synchrony, and timing of parturition

• Published in: Wildlife Society bulletin 2014-12, Vol.38 (4), p.806-811
• Main Authors: Freeman, Eric D., Larsen, Randy T., Peterson, Mark E., Anderson Jr, Charles R., Hersey, Kent R., Mcmillan, Brock R.
• Format: Article
• Language: English
• Subjects: Deer; male/female ratio; Mating behavior; Mule deer; Odocoileus hemionus; Original Articles; Parturition; Population dynamics; Population growth; Pregnancy; rates of pregnancy; Reproduction; Sex ratio; synchrony; synchrony, timing of parturition; timing of parturition; ungulate management; Wildlife management
• ISSN: 1938-5463; 1938-5463; 2328-5540
• DOI: 10.1002/wsb.450

Evaluating how management practices influence the population dynamics of ungulates may enhance future management of these species. For example, in mule deer (Odocoileus hemionus), changes in male/female ratio due to male-biased harvest may alter rates of pregnancy, timing of parturition, and synchrony of parturition if inadequate numbers of males are present to fertilize females during their first estrous cycle. If rates of pregnancy or parturition are influenced by decreased male/female ratios, recruitment may be reduced (e.g., fewer births, later parturition resulting in lower survival of fawns, and a less synchronous parturition that potentially increases susceptibility of neonates to predation). Our objectives were to compare rates of pregnancy, synchrony of parturition, and timing of parturition between exploited mule deer populations with a relatively high (Piceance, CO, USA; 26 males/100 females) and a relatively low (Monroe, UT, USA; 14 males/100 females) male/female ratio. We determined rates of pregnancy via ultrasonography and timing of parturition via vaginal implant transmitters. We found no differences in rates of pregnancy (98.6% and 96.6%;z= −0.821;P= 0.794), timing of parturition (estimate = 1.258; SE = 1.672;t= 0.752;P= 0.454), or synchrony of parturition (F= 1.073P= 0.859) between Monroe Mountain and Piceance Basin, respectively. The relatively low male/female ratio on Monroe Mountain was not associated with a protracted period of parturition. This finding suggests that relatively low male/female ratios typical of heavily harvested populations do not influence population dynamics because recruitment remains unaffected.