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Population-scale Impacts of the Road Network on Maned Wolves in Brazil: Insights from a Mechanistic Simulation Model
Citation:
Schumaker, N., P. Barbosa, AND C. Grilo. Population-scale Impacts of the Road Network on Maned Wolves in Brazil: Insights from a Mechanistic Simulation Model. International Conference on Ecology & Transportation, Sacramento, CA, September 22 - 26, 2019.
Impact/Purpose:
The US Environmental Protection Agency developed the HexSim life history simulator to improve risk assessments, particularly those involving pesticides, by assessing impacts to wildlife populations. Animal populations are often distributed across large complex landscapes, which can subject individuals to a complex array of interacting natural and anthropogenic stressors. This study examined one particularly ubiquitous non-chemical stressor common to most modern landscapes – roads carrying automobile traffic. This presentation reports on our examination of how roads structure wildlife populations by altering growth and occupancy rates, and thereby alter the likelihood and magnitude of affects attributable to other disturbance regimes.
Description:
The maned wolf (Chrysocyon brachyurus) is a South American canid classified as Near Threatened by the IUCN, and is presently found mainly in the Brazilian Savannah. The species is experiencing roadkill rates estimated to range from 0.011 to 0.083 ind./km/year, and its low population densities and reproductive output make it particularly vulnerable to road impacts. Yet little is known about the effects that roads are having on maned wolf population size, distribution, and dynamics. We developed a spatially-explicit, individual-based population model for this system, and used it to explore a range of assumptions regarding the outcome of maned wolf interactions with roads by varying the probabilities of avoidance, successful road crossing, and roadkill mortality. We found that, relative to a no-impact baseline, even moderate rates of road mortality led to severe declines in population size, and that four specific locations accounted for a disproportionate fraction of roadkill events. We also quantified changes in simulated occupancy patterns and source-sink distributions associated with road-induced resource fragmentation. After further refinement, our model and methods might be used to guide mitigation efforts and to forecast future impacts associated with Brazil’s rapidly expanding road network. This work should be valuable to researchers attempting to quantify road impacts on wildlife in other ecological systems.