Walking the line: Investigating biophysical characteristics related to wildlife use of linear features

AbstractHabitat restoration is a necessary component of wildlife conservation in anthropogenic landscapes. To ensure restoration initiatives achieve the desired effects on wildlife communities, it is useful to investigate how animals use landscape features. Understanding the relationships between wildlife use and ecological cues provides specific and measurable targets that can be used to measure restoration success. In western Canada, linear feature networks formed by seismic lines, pipelines, and roads have altered the boreal forest landscape and resulted in population declines for woodland caribou. Restoration is aimed at supporting caribou recovery by deterring linear feature use by caribou predators and ungulate competitors. Information on how linear feature characteristics facilitate or deter wildlife use supports restoration initiatives by providing specific targets for restoration. Here, we used wildlife track and sign data to investigate biophysical characteristics related to the use of linear features by canines, bears, deer, elk, and moose in caribou ranges of west-central and north-western Alberta and British Columbia. We built generalized linear mixed models consistent with three hypotheses that could explain likely mechanisms for use: 1) ease of movement, 2) risk avoidance, and 3) resource availability (prey and forage). Moose, deer, elk, and bears were more likely to use linear features with either human or game trails. Bears and canines were less likely to use seismic lines with greater lateral vegetation cover and taller vegetation, respectively. Moose, deer, and elk were more likely to use linear features with greater cover of ungulate forage taxa such as willow, birch, sedges, and forbs. These results suggest that restoration focusing on trails, online vegetation structure, and online vegetation type should deter predators and ungulate prey species to the overall benefit of caribou. Our study corroborates the findings of other research recommending structural and functional restoration utilizing high-intensity line blocking and vegetative regeneration. We provide specific targets for linear feature restoration to assist in prioritization according to restoration objectives, which translates to a broader goal of linking local-level restoration actions to landscape-level conservation goals. This approach to restoration has implications for any major system experiencing anthropogenic landscape change., MethodsThe study areas consisted of caribou ranges in west-central and north-western Alberta and British Columbia, Canada. The west-central area included four caribou ranges – Little Smoky, A la Peche, and the Alberta portions of Redrock-Prairie Creek and Narraway outside of protected areas (-117˚ W to -120˚ W, 53˚ N to 55˚ N). The north-western area included the Chinchaga range on both sides of the provincial border (-117˚ W to -122˚ W, 56˚ N to 58˚ N; Fig. 1). The areas totaled 47,100 km2 and contained over 92,943 km of linear features, including seismic lines, pipelines, and inactive forestry roads. The primary goal of field data collection was to collect information on human use of linear features. Using a geographic information system (GIS) and a random number generator, we selected linear features that intersected access roads. We created a unique identifier for each linear feature (LineID) and established three plots at 0m, 100m, and 500m away from the intersecting access road. We visited all west-central and north-western seismic line sampling sites in June–October 2014, 2015, and north-western pipeline sites in August 2017 to record wildlife and human linear feature use, collect field measurements of linear feature and surrounding forest characteristics, and identify vegetation taxa. On the linear feature (‘online’), we identified tracks, scat, and any other wildlife and human sign. We classified canines (wolves and coyotes, C. latrans), bears (black bears, U. americanus, and grizzly bears, U. arctos), and deer (white-tailed deer, O. virginianus, and mule deer, O. hemonius) at the genus level and caribou, moose, and elk at the species level. To account for weather impacts on tracks and signs, we assigned a confidence level to each observation, and only included observations assigned confidence levels of ‘reasonably certain’ and ‘certain’ in statistical modelling. We measured an average online lateral vegetation cover from cover board measurements taken in both directions from the plot, measured average vegetation height, recorded soil moisture, and the presence/absence of human and game trails (see Pigeon et al., 2016 for details). In the surrounding forest (‘offline’, 15m from the linear feature), we again measured lateral vegetation cover and average tree height. To record vegetation composition data, we established online 10m2 and 1m2 subplots at the plot 100m from the access road; we only recorded vegetation composition data within this plot because of limited time and resources for field data collection. Within these subplots, we identified and recorded the percent ground cover of vegetation taxa used as forage by bears and caribou alternate competitors. We standardized and scaled continuous and percent variables prior to modelling., Usage notesAll data were processed using R programming software (R Core Team, 2019).

摘要：生境修复（habitat restoration）是人为景观（anthropogenic landscapes）中野生动物保护的必要组成部分。为确保修复举措对野生动物群落达成预期效果，探究动物如何利用景观特征具有重要意义。明晰野生动物利用与生态线索间的关联，可为衡量修复成效提供具体可量化的目标。在加拿大西部，由地震勘探线（seismic lines）、管道（pipelines）及道路构成的线性特征（linear feature）网络改变了北方森林景观，并导致林地驯鹿（woodland caribou）种群数量下降。修复工作旨在通过阻止驯鹿的捕食者与有蹄类竞争者（ungulate competitors）使用线性特征，助力驯鹿种群恢复。有关线性特征特性如何促进或阻碍野生动物利用的信息，可为修复举措提供具体目标，从而支持相关工作开展。本研究利用野生动物足迹与痕迹数据，针对加拿大阿尔伯塔省中西部、西北部以及不列颠哥伦比亚省的驯鹿分布区内，犬科动物（canines）、熊类（bears）、鹿类（deer）、马鹿（elk）及驼鹿（moose）对线性特征的利用情况，探究其相关生物物理特征。我们构建了契合三种可解释利用潜在机制的广义线性混合模型（generalized linear mixed models）：1）移动便利性，2）风险规避，3）资源可获得性（猎物与饲草）。驼鹿、鹿类、马鹿及熊类更倾向于使用带有人类步道或兽径的线性特征。熊类与犬科动物分别更少使用侧向植被覆盖度更高、植被更高的地震勘探线。驼鹿、鹿类及马鹿更倾向于使用存在更多有蹄类饲草类群（如柳树、桦树、莎草及草本植物）覆盖的线性特征。研究结果表明，聚焦步道、在线植被结构与在线植被类型的修复工作，可对捕食者与有蹄类猎物物种产生威慑作用，整体惠及驯鹿种群。本研究印证了其他研究的结论，即建议通过高强度线路封堵与植被再生开展结构与功能修复。我们为线性特征修复提供了具体目标，以助力依据修复目标确定优先级，这一工作可进一步实现将局部修复行动与景观尺度保护目标相衔接的整体目标。此类修复方法对所有经历人为景观变化的大型生态系统均具有借鉴意义。

研究方法：本研究的调查区域涵盖加拿大阿尔伯塔省中西部、西北部以及不列颠哥伦比亚省的驯鹿分布区。中西部区域包含4处驯鹿分布区——小斯莫基（Little Smoky）、拉佩什（A la Peche），以及雷德洛克-普雷里克里克与纳拉韦在阿尔伯塔省的未受保护区域（西经117°至120°，北纬53°至55°）。西北部区域包含横跨省界的钦查加（Chinchaga）分布区（西经117°至122°，北纬56°至58°；图1）。调查区域总面积达47100平方千米，包含超过92943千米的线性特征，包括地震勘探线、管道以及废弃林业道路。野外数据采集的核心目标为收集线性特征的人类利用信息。我们借助地理信息系统（geographic information system, GIS）与随机数生成器（random number generator），选取与通行道路相交的线性特征。为每个线性特征创建唯一标识符（LineID），并在距相交通行道路0米、100米、500米处各设置3个样地。我们于2014年6月至10月、2015年6月至10月走访了中西部与西北部的所有地震勘探线采样点，并于2017年8月走访了西北部的管道采样点，以记录野生动物与人类对线性特征的利用情况、采集线性特征及周边森林特征的野外测量数据，并鉴定植被类群。在线性特征之上（即“在线”样地），我们识别了足迹、粪便及其他野生动物与人类痕迹。我们将犬科动物（狼与郊狼，*C. latrans*）、熊类（美洲黑熊*U. americanus*与灰熊*U. arctos*）、鹿类（白尾鹿*O. virginianus*与骡鹿*O. hemonius*）鉴定至属水平，将驯鹿、驼鹿与马鹿鉴定至种水平。为考量天气对足迹与痕迹的影响，我们为每一条观测记录赋予置信等级，仅将置信等级为“相当确定”与“确定”的观测纳入统计建模。我们通过在样地两侧使用覆盖板测量法获取平均在线侧向植被覆盖度，测量平均植被高度，记录土壤湿度，以及记录人类步道与兽径的存在与否（详细方法参见Pigeon等，2016）。在周边森林区域（即“离线”样地，距线性特征15米处），我们同样测量了侧向植被覆盖度与平均树高。为采集植被组成数据，我们在距通行道路100米的样地内设置了10平方米与1平方米的在线子样地；由于野外数据采集的时间与资源有限，我们仅在该样地内记录植被组成数据。在这些子样地中，我们鉴定并记录了被熊类与驯鹿的替代竞争者用作饲草的植被类群的地面盖度百分比。在建模前，我们对连续变量与百分比变量进行了标准化与缩放处理。

使用说明：所有数据均通过R编程语言软件（R Core Team, 2019）处理完成。