Animal mortality resulting from collisions with vehicles has emerged as a major human-caused threat to wildlife. While direct mortality of wildlife from vehicles has been well documented, fewer studies have focussed on the population-level effects of road mortality, particularly due to low-traffic volume roads. We conducted a population viability analysis (PVA) on western rattlesnakes Crotalus oreganus occupying a protected area with low road density and an average traffic volume of ≈350 vehicles d−1, near the northern periphery of the species’ range. We used the program Vortex with a field-derived database on road mortality, population demography, and extent of occurrence. The model showed that although the population had a high likelihood of persistence over the next 100 yr (extinction probability <0.01), a substantial decline was projected (stochastic growth rate −0.035, 97% decrease in mean population size, from 2131 to 72) under the current road mortality rate (6.6% of population yr−1); any increases in road mortality rates were projected to cause extirpation in under 100 yr. Our study provides strong evidence that road mortality is and will continue to be a significant contributor to the decline of this threatened species, even without higher traffic volumes and other significant anthropogenic impacts.

中文翻译：

---

当保护区不够时：预计低通行道路将导致北方毒蛇种群减少

与车辆相撞导致的动物死亡已成为人为对野生动物造成的主要威胁。虽然车辆直接导致野生动物死亡已有详细记录，但很少有研究关注道路死亡对人口的影响，特别是由于道路交通量低。我们对西部响尾蛇 Crotalus oreganus 进行了种群生存力分析 (PVA)，该保护区位于该物种分布范围的北部边缘，道路密度低，平均交通量约为 350 辆 d-1。我们将 Vortex 程序与一个关于道路死亡率、人口统计和发生范围的现场衍生数据库一起使用。该模型表明，尽管该种群在未来 100 年中极有可能持续存在（灭绝概率 <0.01），在当前的道路死亡率（人口 yr-1 的 6.6%）下，预计将大幅下降（随机增长率 -0.035，平均人口规模减少 97%，从 2131 年到 72 年）；预计道路死亡率的任何增加都会在 100 年内导致灭绝。我们的研究提供了强有力的证据，表明即使没有更高的交通量和其他重大的人为影响，道路死亡率仍然是并将继续成为这种受威胁物种数量减少的重要原因。