Data from: Blood does not buy goodwill: allowing culling increases poaching of a large carnivore

Quantifying environmental crime and the effectiveness of policy interventions is difficult because perpetrators typically conceal evidence. To prevent illegal uses of natural resources, such as poaching endangered species, governments have advocated granting policy flexibility to local authorities by liberalising culling or hunting of large carnivores. We present the first quantitative evaluation of the hypothesis that liberalising culling will reduce poaching and improve population status of an endangered carnivore. We show that allowing wolf (Canis lupus) culling was significantly more likely to increase poaching than reduce it. Replicated, quasi-experimental changes in wolf policies in Wisconsin and Michigan, USA, revealed that a repeated policy signal to allow state culling triggered repeated slow-downs in wolf population growth, irrespective of the policy implementation measured as the number of wolves killed. The most likely explanation for these slow-downs was poaching and alternative explanations found no support. When the government kills a protected species, the perceived value of each individual of that species may decline; so liberalizing wolf culling may have sent a negative message about the value of wolves or acceptability of poaching. Our results suggest that granting management flexibility for endangered species to address illegal behaviour may instead promote such behaviour.

由于不法行为人通常会销毁证据，量化环境犯罪行为及其政策干预的实施成效向来颇具难度。为遏制诸如偷猎濒危物种等自然资源非法利用行为，各国政府历来主张通过放宽大型食肉动物的猎杀或狩猎政策，赋予地方当局政策灵活性。本研究首次针对“放宽猎杀政策可减少偷猎、改善濒危食肉动物种群状况”这一假说开展量化评估。研究结果显示，允许猎杀灰狼（Canis lupus）反而更有可能加剧偷猎行为，而非减少偷猎。针对美国威斯康星州与密歇根州灰狼政策开展的可重复准实验分析显示，即便以猎杀灰狼数量衡量的政策执行情况存在差异，反复释放的“允许州内猎杀”政策信号仍会持续引发灰狼种群增长放缓。上述种群增长放缓的最合理解释为偷猎行为，其他备选假说均未获得实证支撑。当政府猎杀受保护物种时，该物种个体的公众感知价值可能会下降；因此，放宽灰狼猎杀政策可能传递了“灰狼价值低下、偷猎行为可被接受”的负面信号。本研究结果表明，为应对非法行为而赋予濒危物种管理灵活性，反而可能助长此类非法行为。