Variable duration of reproductive suppression in male coyotes (Canis latrans) treated with a high dose of the gonadotrophin-releasing hormone agonist deslorelin.

Effective and humane management strategies for coyotes (Canis latrans) remain elusive. We hypothesised that exposure to a high dose of a gonadotrophin-releasing hormone (GnRH) agonist would cause prolonged suppression of the reproductive axis. Two groups of male coyotes were administered 47mg deslorelin in the form of either five 9.4-mg controlled-release Suprelorin (Peptech Animal Health, Macquarie Park NSW, Australia) implants (n=3) or 10 4.7-mg implants (n=5). In the first group, deslorelin suppressed plasma LH, testosterone and testes volume in two of three coyotes for three breeding seasons. In the second group, two of five deslorelin-treated coyotes had no sperm production after 1 year and plasma LH, FSH, testosterone and testes volume were suppressed. Although plasma gonadotropins and testosterone were suppressed in three treated coyotes in group two, testes volume and sperm production were evident. Because the duration of suppression differed among individual coyotes, we further hypothesised that a variation in deslorelin release underlay the variability. To test this, we analysed in vivo plasma profiles of deslorelin concentrations. These profiles suggested that deslorelin concentrations >100 pg mL-1 are required to maintain suppression in male coyotes. For field implementation, the development of an implant capable of releasing deslorelin for the life of the coyote is necessary.

Contraception has gone to the coyotes (Canis latrans).

Coyotes (Canis latrans) are predators of livestock. Current management programs, primarily lethal control, are ineffective for long-term management of predation. Controlling reproduction of coyotes may reduce depredations if territory fidelity is maintained by breeding pairs. Surgical sterilization is successful in altering predatory behaviors of coyotes but may provide a challenge for field implementation. An alternative approach is the development of a one-time non-transferable chemical contraceptive. This research is investigating the efficacy of a single high dose treatment of a sustained release gonadotropin-releasing hormone agonist, deslorelin, on coyotes as a long term contraceptive. Male coyotes were administered 47 mg deslorelin subcutaneously. Preliminary data show full suppression of the reproductive axis for over 12 mo as indicated by complete absence of sperm.