One-time administration of the SpayVac ® vaccine prevents pregnancy in red deer (Cervus elaphus) in a temperate forest ecosystem

Abstract Contraception has traditionally been used on domesticated and captive animals, but it has also found increasing application in locally overabundant wildlife species. Different immunocontraceptives are available and they vary in their mechanisms, effectiveness, and potential side-effects. In this study, the porcine zona pellucida (pZP)-based vaccine SpayVac ® was administered to red deer ( Cervus elaphus ) in the Bavarian Forest National Park and its contraceptive effectiveness was assessed for one year under field conditions. Twenty red deer were vaccinated with a single intramuscular injection, with 27 additional animals serving as controls. All 47 deer were fitted with GPS collars. Reproduction was tracked by observing calves using camera trap surveys and by measuring the concentrations of fecal progesterone metabolites to determine pregnancy. SpayVac ® reduced fertility to 11% in vaccinated deer compared to a fertility rate of 86% in control animals for one year. Camera traps and/or progesterone metabolites aided in evaluating the reproductive status of 85% of the studied female red deer. Specifically, reproductive status was determined in 37 of 46 individuals using camera traps, and pregnancy in 19 of 46 females using progesterone metabolites. In all but one deer, the same results were obtained with the two methods. Our study demonstrates the 1-year efficacy of SpayVac ® immunocontraception in red deer. It also describes methods for the improved determination of pregnancy status and calf presence in wildlife, using camera traps and fecal progesterone metabolites. Studies evaluating the long-term contraceptive effectiveness and the effects of fertility control on population structure and behavior are still needed.