An accurate understanding of harvest trends is required for effective wildlife management. Trapper harvest data represent valuable long‐term data for evaluating patterns and trends for wildlife species at broad spatiotemporal scales. Inferring accurate trends from harvest data, however, first requires identifying and controlling for confounding factors that vary independent of abundance. We investigated trends in 43 years of trapper harvest data (1976–2018) from Illinois, USA, for red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), and coyote (Canis latrans) while controlling for factors that may affect trapper effort, including number of effective (i.e., successful) trappers, pelt price, gasoline price, winter unemployment, and winter weather conditions. Annual trapper harvest for red and gray foxes declined and was affected by gasoline price and winter unemployment, whereas annual trapper harvest for coyotes increased and was not strongly affected by other covariates. After adjusting for pelt price, harvest of red foxes was relatively stable, but harvest of gray foxes declined and harvest of coyotes increased. Effects of covariates on harvest per successful trapper varied by species; nevertheless, we detected an increasing trend for coyotes and decreasing trends for gray foxes and red foxes. Concordance across indices for gray foxes and coyotes was consistent with hypothesized declines for gray foxes and increases for coyotes in the midwestern United States. Trends for red foxes varied depending on how we accounted for potential confounding factors and it is unclear if these trends suggest population declines or distribution shifts to urban areas with reduced trapping susceptibility. Our results highlight the importance of understanding sources of variation in harvest data and that their effects can vary across species. © 2020 The Wildlife Society.

中文翻译：

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识别和控制犬类收获数据的变化

为了有效地进行野生动植物管理，需要对收获趋势有准确的了解。捕捞者的收获数据代表了宝贵的长期数据，可用于在广泛的时空尺度上评估野生生物物种的模式和趋势。但是，首先要从收获数据中推断出准确的趋势，就需要识别和控制与丰度无关的混杂因素。我们调查了来自美国伊利诺伊州的43年捕兽器收获数据（1976-2018）的趋势，其中包括红狐狸（Vulpes vulpes），灰狐狸（Urocyon cinereoargenteus）和土狼（Canis latrans），同时控制可能影响捕捞者努力的因素，包括有效（即成功）的捕捞者数量，毛皮价格，汽油价格，冬季失业率和冬季天气情况。红狐和灰狐的年捕集器收成下降，并且受汽油价格和冬季失业的影响，而土狼的年捕集器收成增加，并且不受其他协变量的强烈影响。调整毛皮价格后，红狐狸的收获相对稳定，但灰狐狸的收获减少了，土狼的收获增加了。协变量对每个成功捕捞者的收获的影响因物种而异；但是，我们发现土狼有增加的趋势，而灰狐和红狐有下降的趋势。在美国中西部，灰狐和土狼的各项指标之间的一致性与假设的灰狐下降和土狼的上升相一致。狐狸的趋势根据我们如何考虑潜在的混杂因素而有所不同，目前尚不清楚这些趋势是否表明人口减少或分布转移到城市的诱捕敏感性降低。我们的结果凸显了理解收获数据变异源的重要性，并且它们的影响会因物种而异。©2020野生动物协会。我们的结果凸显了理解收获数据变异源的重要性，并且它们的影响会因物种而异。©2020野生动物协会。我们的结果凸显了理解收获数据变异源的重要性，并且它们的影响会因物种而异。©2020野生动物协会。