Duncan Calvin L, King Julie L, Stapp Paul
Department of Biological Science, California State University, Fullerton, CA 92831, USA (CLD, PS).
Catalina Island Conservancy, Avalon, CA 90704, USA (CLD, JLK).
J Mammal. 2017 Oct 3;98(5):1272-1287. doi: 10.1093/jmammal/gyx087. Epub 2017 Aug 10.
In late 2009, the Catalina Island Conservancy began using fertility control to replace periodic removals to manage an introduced population of American bison () on the island. Through the application of the immunocontraceptive vaccine porcine zona pellucida (PZP), population growth was slowed within 1 year, and halted over time. In response to lingering questions about the use of PZP to manage large, free-ranging wildlife populations, we sought to determine the reversibility of PZP by ceasing the annual application to a subset of 15 bison cows and monitoring for subsequent calf arrival, and to document changes in the timing and length of the breeding season in response to PZP by monitoring breeding behavior and assessing fecal progesterone (FP) levels for all 60 resident cows over a 13-month period. As of June 2017, no new calves had been observed on the island, suggesting that, following repeated annual treatment with PZP (3 or 4 years), bison do not resume normal reproduction for at least 4 or 5 years, and that fewer treatments would be advisable if a faster return to fertility is desired. Based on observations of bull and cow behavior, and FP levels, cows displayed estrous cycles consistently throughout the study period, indicating that bison may ovulate year-round when conception and its consequences, e.g., lactation and presence of calves, are blocked. Because there is little evidence that an extended breeding season would negatively impact the health of bulls or result in large numbers of out-of-season births on Catalina, PZP appears to be a highly effective tool for managing the population of introduced bison on the island. However, the extended period of contraception and breeding activity of both cows and bulls may make PZP less suitable in high-latitude, predator-rich environments where bison conservation remains a top priority.
2009年末，卡特琳娜岛保护协会开始使用生育控制手段来取代定期迁移，以管理岛上引入的美洲野牛种群。通过应用免疫避孕疫苗猪透明带（PZP），种群增长在1年内放缓，并随着时间推移停止。针对关于使用PZP管理大型、自由放养野生动物种群的持续疑问，我们试图通过停止对15头母野牛的年度用药并监测后续小牛出生情况来确定PZP的可逆性，并通过监测繁殖行为和评估13个月内所有60头常住母牛的粪便孕酮（FP）水平，记录繁殖季节的时间和长度因PZP而发生的变化。截至2017年6月，岛上未观察到新的小牛，这表明在用PZP进行反复年度治疗（3或4年）后，野牛至少4或5年内不会恢复正常繁殖，并且如果希望更快恢复生育能力，建议减少治疗次数。基于对公牛和母牛行为以及FP水平的观察，母牛在整个研究期间持续表现出发情周期，表明当受孕及其后果（如哺乳和小牛的存在）受到阻碍时，野牛可能全年排卵。由于几乎没有证据表明延长繁殖季节会对公牛健康产生负面影响或导致卡特琳娜岛上大量非季节性出生，PZP似乎是管理岛上引入野牛种群的高效工具。然而，母牛和公牛避孕及繁殖活动的延长时期可能使PZP在高纬度、捕食者丰富的环境中不太适用，在这些环境中野牛保护仍然是首要任务。
