Spatial-temporal dynamics of hunter effort for wild turkeys in Michigan

Wild turkeys (Meleagris gallopavo; hereafter turkeys) are an important game animal whose popularity among hunters has increased in recent decades. Yet, the number of hunters pursuing turkeys appears to be in flux, patterns of hunter abundance have primarily been described at broad spatial scales, and the ability of management to impact hunter numbers in the post-restoration era of management through opportunity for quality hunting is unclear. We used county-scale estimates of turkey hunter numbers collected over a 14-year period (2001–2014) and time-series analyses to evaluate the spatial scales at which spring and fall turkey hunter populations fluctuate, and also used generalized linear mixed models to evaluate whether attributes related to quality turkey hunting explain recent patterns in hunter abundance. We found heterogeneity in turkey hunter population growth at finer spatial scales than has been previously described (i.e., counties and management units), and provide evidence for spatial structuring of hunter population dynamics among counties that did not always correspond with existing management units. Specifically, the directionality of hunter population change displays spatial structure along an east-west gradient in southern Michigan. We also found little evidence that factors providing opportunity for quality turkey hunting had meaningful impacts on recent spatial-temporal patterns of hunter numbers. Our results imply that providing quality turkey hunting opportunities alone may be insufficient for sustaining populations of turkey hunters in the future, and that modern determinants of hunter participation extend beyond the availability of abundant turkey populations. Moreover, our results demonstrate that interpretation of harvest data as indices of abundance for turkey populations is difficult in the absence of hunter effort data, as changes to turkey harvest are a function of potentially fine-scaled changes in populations of hunters, not simply changes to turkey populations.

野火鸡（Meleagris gallopavo，下称火鸡）是一类重要的猎用动物，近几十年来其在猎人群体中的受欢迎程度持续攀升。然而，参与火鸡狩猎的猎人数量似乎处于动态波动之中，现有关于猎人种群丰度的分布模式研究多聚焦于大空间尺度，且在种群恢复后的管理阶段，通过提供优质狩猎机会来调控猎人数量的实际效果尚不明确。本研究采用2001-2014年共14年间收集的县级火鸡猎人数量估算数据，结合时间序列分析，探究春秋季火鸡猎人种群波动的空间尺度；同时使用广义线性混合模型（generalized linear mixed models），检验与优质火鸡狩猎相关的属性是否能够解释近期猎人丰度的分布模式。研究发现，火鸡猎人种群增长的异质性出现在比此前研究更精细的空间尺度上（即县级与管理单元尺度），且证据表明各县间的猎人种群动态存在空间结构，但该结构并不总是与现有管理单元相匹配。具体而言，密歇根州南部的猎人种群变化方向沿东西向梯度呈现显著的空间分布特征。此外，本研究未发现足够证据表明，能够提供优质火鸡狩猎机会的相关因素会对猎人数量的近期时空分布模式产生实质性影响。研究结果显示，仅通过提供优质火鸡狩猎机会，或不足以在未来维持火鸡猎人种群规模；同时，现代影响猎人参与度的决定因素已远超火鸡种群丰度的可获得性范畴。此外，本研究结果还表明，在缺乏猎人狩猎努力数据的前提下，将狩猎数据作为火鸡种群丰度的指标进行解读存在较大难度——因为火鸡狩猎量的变化取决于猎人种群潜在的精细尺度变化，而非仅由火鸡种群本身的变化所决定。