Fertility of red deer in relation to area, age, body mass, and mandible length

Abstract

We examined variation in fertility rates of red deer (Cervus elaphus) in five areas that cover a range of habitats in Belgium: Hautes Fagnes (3), middle of Ardenne (1) and Famenne (1). In all areas, the majority of females ovulated for the first time as yearlings. The fertility rate (percentage of females ovulating) of yearlings varied from 0.48 to 0.91 between areas. The proportion of ovulating females 2-to-7-year-old exceeded 0.99 in all areas. The fertility rate decreased from 0.94 to 0.86 in 8-to-11-year-old females and fell to 0.50 in 12-year olds. We developed logistic model to assess how age, body mass, mandible length, and area were linked to fertility in different age-classes. In yearlings, mandible length, body mass and area variations were all significandy related to fertility when fitted individually. However, body mass explained the best the variation in fertility. In the 1-to-7-year-old females, mandible length, body mass, age, and area variations were all significant when fitted individually to fertility. Mandible length was the most significant variable, but adding body mass in the model improved the fit significantly. Although we observed significant between-area variations in fertility rate of yearlings, adding area in the logistic model did not improve the fits. This suggests that the fertility-mass relationship is the same between the five areas and that variation in fertility between areas reflects essentially between-area variations in mandible length and body mass.