Data from: Compensatory selection for roads over natural linear features by wolves in northern Ontario: implications for caribou conservation

Woodland caribou (Rangifer tarandus caribou) in Ontario are a threatened species that have experienced a substantial retraction of their historic range. Part of their decline has been attributed to increasing densities of anthropogenic linear features such as trails, roads, railways, and hydro lines. These features have been shown to increase the search efficiency and kill rate of wolves. However, it is unclear whether selection for anthropogenic linear features is additive or compensatory to selection for natural (water) linear features which may also be used for travel. We studied the selection of water and anthropogenic linear features by 52 resident wolves (Canis lupus x lycaon) over four years across three study areas in northern Ontario that varied in degrees of forestry activity and human disturbance. We used Euclidean distance-based resource selection functions (mixed-effects logistic regression) at the seasonal range scale with random coefficients for distance to water linear features, primary/secondary roads/railways, and hydro lines, and tertiary roads to estimate the strength of selection for each linear feature and for several habitat types, while accounting for availability of each feature. Next, we investigated the trade-off between selection for anthropogenic and water linear features. Wolves selected both anthropogenic and water linear features; selection for anthropogenic features was stronger than for water during the rendezvous season. Selection for anthropogenic linear features increased with increasing density of these features on the landscape, while selection for natural linear features declined, indicating compensatory selection of anthropogenic linear features. These results have implications for woodland caribou conservation. Prey encounter rates between wolves and caribou seem to be strongly influenced by increasing linear feature densities. This behavioral mechanism - a compensatory functional response to anthropogenic linear feature density resulting in decreased use of natural travel corridors - has negative consequences for the viability of woodland caribou.

安大略省的林地驯鹿（Rangifer tarandus caribou）是受威胁物种，其历史分布区已大幅缩减。其种群衰退的部分原因可归结为人为线性设施（anthropogenic linear features）的密度不断升高，包括步道、道路、铁路与电力输电线路。已有研究表明，此类设施可提升灰狼的搜索效率与猎杀成功率。然而目前尚不明确，对人为线性设施的选择，是与对自然（水体）线性设施的选择呈累加效应，还是存在补偿替代效应——尽管灰狼也会利用水体线性设施进行移动。本研究针对安大略北部三个林业活动与人类干扰程度各异的研究区域，对52只定居灰狼（Canis lupus × lycaon）在四年间对水体线性设施与人为线性设施的选择偏好展开了研究。我们在季节活动范围尺度下，采用基于欧几里得距离的资源选择函数（mixed-effects logistic regression，混合效应逻辑回归），为水体线性设施、主次道路/铁路、电力线路以及三级道路的距离设置随机系数，在考量每种设施可获得性的前提下，估算每种线性设施与多种生境类型的选择强度。随后我们探究了人为线性设施与水体线性设施选择偏好之间的权衡关系。结果显示，灰狼会同时选择人为与水体线性设施；在育幼季（rendezvous season），灰狼对人为设施的选择强度高于水体设施。随着景观中人为线性设施密度的升高，灰狼对这类设施的选择偏好增强，而对自然线性设施的选择偏好则出现下降，这表明灰狼对人为线性设施的选择存在补偿替代效应。上述结果对林地驯鹿的保护具有重要启示。狼与驯鹿的猎物相遇率似乎会随线性设施密度升高而显著上升。这种行为机制——即对人为线性设施密度产生的补偿性功能响应（compensatory functional response），导致狼减少了对自然移动廊道的使用——会对林地驯鹿的种群存续能力产生负面影响。