Data from: Pedigree analysis reveals a generational decline in reproductive success of captive Tasmanian devil (Sarcophilus harrisii): implications for captive management of threatened species

Captive breeding programs are an increasingly popular tool to augment the conservation of threatened wild populations. Many programs keep detailed pedigrees, which are used to prescribe breeding targets to meet demographic and genetic goals. Annual breeding targets are based on previous productivity, but do not account for changes in reproductive success that may occur over generations in captivity and which may impair the ability of a program to meet its goals. We utilise a large studbook from the Tasmanian devil (Sarcophilus harrisii) captive breeding program to investigate biological, genetic and environmental factors that affect variation in reproductive success among individuals and over generations of captive breeding. Reproductive success declined with increasing generations in captivity: wild-born females had a 56.5% chance of producing a litter compared to a 2.8% chance for generation 5 captive-born females (N = 182) and when they did, wild-born females produced more offspring (3.1 joeys, 95% CI: 2.76 - 3.38, compared to 2.7 joeys, 95% CI: 2.55 - 2.90, in captive-born females [N = 105]). Reproductive success also declined as dam age at first breeding increased. Our results reveal a conflict with the widely-cited conservation strategy to limit opportunity for selection by extending generation length through delaying reproduction, as captive breeding programs that delay female breeding with this goal in mind risk reduced productivity. Our data demonstrate the benefit of pedigree analysis to identify biological processes that reveal crucial trade-offs with conservation best-practice.人工繁育项目已日益成为强化濒危野生种群保护的重要工具。诸多项目会留存详尽的谱系（pedigree）记录，用于制定繁育目标以达成种群统计与遗传保护目标。当前的年度繁育目标多基于过往繁育效能制定，但未考虑人工繁育多代过程中繁殖成功率可能发生的变化，而此类变化可能削弱项目达成既定目标的能力。本研究借助塔斯马尼亚袋獾（Sarcophilus harrisii）人工繁育项目的大型繁育档案（studbook），探究影响个体间及人工繁育多代间繁殖成功率差异的生物、遗传与环境因素。繁殖成功率随人工繁育代数增加而下降：野生起源雌性的产仔概率为56.5%，而第5代人工繁育雌性的产仔概率仅为2.8%（样本量N=182）；即便成功产仔，野生起源雌性的幼崽数量也更多（3.1只幼崽，95%置信区间CI: 2.76-3.38，而人工繁育起源雌性为2.7只幼崽，95%置信区间CI:2.55-2.90，样本量N=105）。繁殖成功率同时随雌性首次繁育年龄的增加而下降。本研究结果揭示，当前被广泛引用的保护策略——通过推迟繁育以延长世代长度从而限制选择压力——存在矛盾：以该目标为导向、推迟雌性繁育的人工繁育项目，反而面临繁育效率下降的风险。本研究数据证实，谱系分析有助于识别出与主流保护实践存在关键权衡取舍的生物学过程。