Data from: Effective implementation of age restrictions increases selectivity of sport hunting of the African lion

1. Sport hunting of wildlife can play a role in conservation but can also drive population declines if not managed sustainably. Previous simulation modelling found that large felid species could theoretically be hunted sustainably by restricting harvests to older individuals that have likely reproduced. Several African countries currently use age-based hunting for lions although the outcomes have yet to be evaluated in a wild population. 2. Here we provide the first empirical evidence that a system of incentives sufficiently encouraged age-based hunting and reduced offtake of a wild felid, thereby reducing the potential risk of unsustainable hunting on a threatened species. We examined long-term hunting data and the lion population trend in Niassa National Reserve, Mozambique. 3. To incentivise hunter compliance, a ‘points’ system was developed which rewards operators that harvest lions older than the 6-year minimum trophy age recommended for sustainable hunting and penalises operators that hunt ‘underage’ lions (<4 years). A key component of this system is the ecological application of key physical traits that predictably change with age in order to estimate (by hunters) and validate (by authorities) trophy individuals’ ages pre- and post-mortem, respectively. Analysis of 138 lion hunts and 87 lion trophies from 2003-2015 revealed that after enforcement of age restrictions in 2006, hunters shifted harvests to suitably aged lions (>6 years), from 25% of offtakes in 2004 to 100% by 2014. 4. Simultaneously, the number of lions and percentage of quota harvested decreased, resulting in lower lion offtakes. Following an initial decrease after enforcement of the aging system, the percentage of hunts harvesting lions stabilised, demonstrating that hunters successfully located and aged older lions. 5. Synthesis and applications. Evidence suggests that age restrictions combined with an incentive-based points system regulated sport hunting and reduced pressure on the lion population. We attribute the successful implementation of this management system to: 1) committed, consistent enforcement by management authorities, 2) genuine involvement of all stakeholders from the start, 3) annual auditing by an independent third party, 4) the reliable, transparent, straight-forward aging process, and 5) the simple, pragmatic points system for incentivising hunter compliance. Our study demonstrates that the use of age restrictions can increase the selectivity of sport hunting and lower trophy offtakes to reduce the possibility of unsustainable sport hunting negatively impacting species populations in the absence of reliable estimates of population size. It must be noted, however, that there was no measurable change in the lion numbers over the past decade that could be attributed to the implementation of this policy alone.1. 野生动物休闲狩猎既可对物种保护发挥积极作用，但若未实施可持续管理，也可能导致种群数量下降。既往模拟建模研究表明，大型猫科动物（large felid species）理论上可通过将狩猎对象限定为已完成繁殖的老龄个体，实现可持续狩猎。目前已有多个非洲国家针对狮子推行基于年龄的狩猎制度，但该制度的野外种群实施效果尚未得到评估。 2. 本研究首次提供实证证据，证明一套激励机制可有效推动基于年龄的狩猎行为，并降低野生猫科动物的狩猎捕获量，从而降低受威胁物种面临的非可持续狩猎风险。我们对莫桑比克尼亚萨国家保护区（Niassa National Reserve）的长期狩猎数据与狮子种群趋势展开了分析。 3. 为激励狩猎者遵守规定，相关方开发了“积分”制度：对狩猎符合可持续狩猎推荐的最低战利品年龄（6岁）的老龄狮子的狩猎运营商予以奖励，对狩猎“未成年”狮子（<4岁）的运营商予以处罚。该制度的核心环节是依托随年龄产生可预测变化的关键身体特征，分别供狩猎者在狩猎前估算个体年龄、供管理方在狩猎后验证个体年龄。对2003-2015年间138次狮子狩猎活动与87件狮子战利品的分析显示，2006年年龄限制政策实施后，狩猎者的狩猎对象转向了符合年龄要求的老龄狮子（>6岁），其占比从2004年的25%升至2014年的100%。 4. 与此同时，狮子种群数量与狩猎配额使用率均有所下降，最终实现了狮子狩猎捕获量的降低。在年龄制度实施后的初期下降后，狮子狩猎活动占比趋于稳定，表明狩猎者已能够成功定位并识别老龄狮子。 5. 综合与应用。研究结果表明，结合激励积分制度的年龄限制政策可规范休闲狩猎行为，降低狮子种群面临的狩猎压力。我们将该管理系统的成功实施归因于以下五点：1）管理当局坚定且持续的执法力度；2）所有利益相关方自项目启动之初便深度参与；3）由独立第三方开展的年度审计；4）流程可靠、透明且简便易行的年龄鉴定方法；5）用于激励狩猎者合规的简洁务实的积分制度。本研究证明，在缺乏可靠种群数量估算数据的前提下，可通过实施年龄限制政策提升休闲狩猎的选择性，降低战利品捕获量，从而规避非可持续休闲狩猎对物种种群造成的负面影响。但需特别说明的是，在过去十年间，并未出现可单独归因于该政策实施的狮子种群数量可测变化。