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ESR 41:131-139 (2020)  -  DOI: https://doi.org/10.3354/esr01017

When protected areas are not enough: low-traffic roads projected to cause a decline in a northern viper population

Stephanie A. Winton1,*, Christine A. Bishop2, Karl W. Larsen3

1Environmental Science Program, Thompson Rivers University, Kamloops, BC, V2C 0C8, Canada
2Science and Technology Branch, Environment and Climate Change Canada, Delta, BC, V4K 3N2, Canada
3Department of Natural Resource Sciences, Thompson Rivers University, Kamloops, BC, V2C 0C8, Canada
*Corresponding author:

ABSTRACT: 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.


KEY WORDS: Western rattlesnake · Crotalus oreganus · Road mortality · Population viability analysis · PVA · Population decline · Extinction risk · Protected areas · Traffic · Demography · Snake


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Cite this article as: Winton SA, Bishop CA, Larsen KW (2020) When protected areas are not enough: low-traffic roads projected to cause a decline in a northern viper population. Endang Species Res 41:131-139. https://doi.org/10.3354/esr01017

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