Male Harvest in Relation to Female Removals in a Black-Tailed Deer Population

The role of density dependence in management of ungulate populations is a debated topic. I tested the effect of female removals on the yield of males in annual public hunting seasons for black-tailed deer (Odocoileus hemionus columbianus) in a 19-year study at Hopland Research and Extension Center, California. Separate treatment and control areas were not available, so pre- and posttreatment control periods were employed to examine for non-treatment effects (i.e., 6 yrs pretreatment, 7 yrs treatment, and 6 yrs posttreatment). During the treatment period, about 20 adult females/year for 3 years and 30/year for 4 years were removed. There was no difference in male harvests between pretreatment and posttreatment control periods (x = 28.5 pre- and 27.3 posttreatment, P = 0.44), so the controls were pooled for testing treatment effects. Male harvest during the treatment period (x = 34.9) was greater than the combined control periods (x = 27.9, P = 0.02). Increased male harvest occurred despite the treatment period coinciding with a 6-year drought. Neither rainfall nor acorn (Quercus spp.) crop was related to male harvest. At the end of the treatment period, combined male harvest and female removal comprised about 21 % of the estimated pre-hunt population. Males taken during the treatment period were younger and weighed less than those taken during control periods. However, 2-year-old males harvested during the treatment period had larger antlers. These results demonstrated that female harvests increased male yield apparently through lowering population density.