Data from: Effects of habitat quality and access management on the density of a recovering grizzly bear population

Human activities have dramatic effects on the distribution and abundance of wildlife. Increased road densities and human presence in wilderness areas have elevated human-caused mortality of grizzly bears and reduced bears' use. Management agencies frequently attempt to reduce human-caused mortality by managing road density and thus human access, but the effectiveness of these actions is rarely assessed.
We combined systematic, DNA-based mark–recapture techniques with spatially explicit capture–recapture models to estimate population size of a threatened grizzly bear population (Kettle–Granby), following management actions to recover this population. We tested the effects of habitat and road density on grizzly bear population density. We tested both a linear and threshold-based road density metric and investigated the effect of current access management (closing roads to the public).
We documented an c. 50% increase in bear density since 1997 suggesting increased landscape and species conservation from management agencies played a significant role in that increase. However, bear density was lower where road densities exceeded 0.6 km/km2 and higher where motorised vehicle access had been restricted. The highest bear densities were in areas with large tracts of few or no roads and high habitat quality. Access management bolstered bear density in small areas by 27%.
Synthesis and applications. Our spatially explicit capture–recapture analysis demonstrates that population recovery is possible in a multi-use landscape when management actions target priority areas. We suggest that road density is a useful surrogate for the negative effects of human land use on grizzly bear populations, but spatial configuration of roads must still be considered. Reducing roads will increase grizzly bear density, but restricting vehicle access can also achieve this goal. We demonstrate that a policy target of reducing human access by managing road density below 0.6 km/km2, while ensuring areas of high habitat quality have no roads, is a reasonable compromise between the need for road access and population recovery goals. Targeting closures to areas of highest habitat quality would benefit grizzly bear population recovery the most.

人类活动对野生动物的分布与丰度具有显著影响。荒野地区道路密度提升及人类活动增多，加剧了人为导致的灰熊（grizzly bear）死亡，同时降低了灰熊对该区域的利用。管理机构通常试图通过管控道路密度以限制人类进入，从而降低人为致死率，但这类措施的有效性却鲜有评估。
本研究结合基于DNA的标记重捕（DNA-based mark–recapture）技术与空间显式标记重捕模型（spatially explicit capture–recapture models），在管理机构采取灰熊种群恢复措施后，对受威胁的凯特-格兰比（Kettle–Granby）灰熊种群的种群规模进行估算。我们检验了生境与道路密度对灰熊种群密度的影响，同时验证了线性与阈值型道路密度指标，并探究了当前通行管理（对公众封闭道路）的效应。
研究记录显示，自1997年以来灰熊种群密度提升了约50%，这表明管理机构加强的景观与物种保护措施对该增长起到了重要作用。然而，当道路密度超过0.6 km/km²时，灰熊种群密度更低；而在机动车通行受限的区域，种群密度更高。最高的灰熊种群密度出现在大片近乎无道路、且生境质量优异的区域。通行管理可使小范围区域内的灰熊种群密度提升27%。
综合与应用。我们的空间显式标记重捕分析表明，在多功能利用景观中，当管理措施聚焦优先保护区域时，种群恢复是可行的。我们认为，道路密度可作为人类土地利用对灰熊种群负面影响的有效替代指标，但仍需考量道路的空间布局。减少道路建设可提升灰熊种群密度，而限制机动车通行同样可达成该目标。本研究证实，将道路密度管控在0.6 km/km²以下以减少人类活动，并确保高生境质量区域无道路通行，这一政策目标是兼顾道路通行需求与种群恢复目标的合理折中方案。针对高生境质量区域实施道路封闭措施，将最有利于灰熊种群的恢复。