Controlling wildlife reproduction : reversible suppression of reproductive function or sex-related behaviour in wildlife species

Fertility control represents a proactive approach to population management for various mammalian wildlife species. In large predators, deslorelin implants have proven to be useful contraceptives in species such as lions, tigers and cheetahs. Although female lions and tigers responded well to various doses of deslorelin, the 9.4 mg implants at 48-month intervals are recommended for treatment of these species. In cheetahs both sexes could be effectively down-regulated using annual 4.7 mg implants. It does however, appear that certain species, like the African wild dog, are more difficult to down-regulate than others. Whether this relates to differences in peripheral deslorelin concentrations achieved or to actual concentrations at the effector site is unknown. Determining peripheral deslorelin concentrations in species like the lion, cheetah and wild dog may provide some answers. LH response to GnRH stimulation at various intervals after deslorelin treatment may also be informative. Additionally, the ability to deliver the implants remotely would make this method of contraception much more appealing to reserve managers. Immunocontraception of free-ranging African elephant cows with the porcine zona pellucida (pZP) vaccine has been shown to be 100% effective in small to medium populations. The protocol followed was three vaccinations (400 μg pZP with Freund’s complete modified adjuvant; 200μg and 200 μg with Freund’s incomplete adjuvants) at 4 to 6-week intervals during the first year followed by a single annual booster (200 μg with Freund’s incomplete adjuvant) thereafter. The vaccine was delivered remotely with darts and thus capture was not required for treatment of the cows. Of the 108 cows treated 62 (57.4%) were pregnant at the time of primary vaccination and calved during Years 1 and 2 of the program. Once these cows had calved, no more calves were born. The method was shown to be safe to use in pregnant cows. A small number of cows developed minor temporary swellings at the dart site. Future research should concentrate on development of slow-release vaccine-formulations that would reduce implementation costs and enable use on larger populations. Although studies are ongoing, there is also a need to expand behavioural studies on treated populations. A GnRH vaccine produced promising results for the down-regulation of androgen-related behaviour in elephant bulls. The bulls were given a primary and two to three booster vaccinations (4 to 7 week intervals) while behaviour and faecal androgen metabolite concentrations were monitored. More intensive studies on animals (African and Asian elephant bulls) of various ages are required to determine whether the treatment is capable of suppressing the annual musth cycles and to establish the effects of GnRH vaccination on male fertilit