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. 野生生物休闲狩猎（sport hunting）既可对物种保护起到积极作用，但若未实施可持续管理，亦可能引发种群数量下滑。此前的模拟模型研究显示，大型猫科动物（felid）理论上可通过仅捕猎已完成繁殖的老年个体，实现可持续狩猎。目前已有多个非洲国家针对狮子采用基于年龄的狩猎模式，但该模式的效果尚未在野生种群中得到评估。
2. 本研究首次提供实证证据，证明一套激励机制可充分推动基于年龄的狩猎模式，并降低野生猫科动物的猎捕量，从而降低受威胁物种遭遇非可持续狩猎的潜在风险。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则，研究团队开发了「积分」系统：对捕猎达到可持续狩猎推荐年龄（≥6岁）的老年狮子的从业者予以奖励，对捕猎「未成年」狮子（<4岁）的从业者予以处罚。该系统的核心环节在于，依托随年龄呈现可预测变化的关键身体特征，建立生态应用方法：分别由狩猎者在猎物生前、管理方在猎物死后，对其年龄进行估算与验证。对2003-2015年间的138次狮子狩猎记录与87份狮子狩猎战利品的分析显示：2006年年龄限制政策实施后，狩猎者的捕猎对象转向符合年龄要求的老年狮子（>6岁），其占比从2004年的25%升至2014年的100%。
4. 与此同时，狮子种群数量与猎捕配额使用率均有所下降，狮子总猎捕量随之降低。年龄限制政策实施后虽出现短期下滑，但狮子狩猎占比随后趋于稳定，这表明狩猎者已能成功定位并准确判断老年狮子的年龄。
5. 综合与应用。研究结果表明，年龄限制与积分激励系统相结合，可规范休闲狩猎行为，减轻狮子种群所承受的狩猎压力。本管理系统得以顺利实施，归因于以下五点：1）管理部门坚定且一贯的执法力度；2）所有利益相关方自项目启动之初便深度参与；3）由独立第三方开展年度审计；4）年龄判断流程可靠、透明且简便易行；5）用于激励狩猎者合规的积分系统简洁务实。本研究证明，在缺乏可靠种群规模估算数据的情况下，实施年龄限制可提升休闲狩猎的选择性，降低战利品狩猎的猎捕量，从而规避非可持续狩猎对物种种群造成负面影响的风险。但需说明的是，过去十年间狮子种群数量未出现可单独归因于该政策实施的可观测变化。