Distribution, Relative abundance, and Roadway Underpass Responses of Carnivores Throughout the Puente-Chino Hills

Abstract

Track surveys were conducted across the Puente-Chino Hills wildlife corridor to determine associations between the distribution and relative abundance of mammals and several landscape variables. Landscape variables were factored into a single variable representing fragmentation. The fragmentation variable was positively associated with the distribution (probability of occurrence at a track transect) and relative abundance (frequency of occurrence at a track transect) of mule deer, striped skunk, domestic dog, and domestic cat and negatively associated with the distribution and relative abundance of bobcat and long-tailed weasel.
\nUnderpasses along seven roadways were monitored to determine associations between the probability and frequency of underpass usage and several landscape and underpass dimension variables. Fragmentation was positively associated with the probability of underpass usage for domestic cats and negatively associated with the probability of underpass usage for coyote, bobcat, and long-tailed weasel. Fragmentation was negatively associated with the frequency of underpass usage for bobcats.
\nUnderpass dimensions were only important in determining the probability of underpass usage for gray fox and mule deer. Coyote, gray fox, mule deer, and domestic cat frequency of underpass usage increased at underpasses that were more open. The amount of natural cover surrounding the underpass entrance was important for bobcat. Fencing and roadway dividers were most effective on coyote use of underpasses. Overall, the probability of underpass usage was primarily dependent on the surrounding landscape variables. The frequency of underpass usage was primarily dependent on the specific underpass dimensions.Given the responses to fragmentation exhibited by bobcats, they represent an excellent target species for conservation in the Puente-Chino Hills. Several measures can be made to enhance connectivity of carnivores throughout this corridor. Habitat acquisition and restoration should be concentrated along the narrowest portions of the corridor and at choke points along roadways. Existing underpasses should be surrounded by natural cover and contain proper fencing to direct wildlife under the roadway. Future underpasses should be large enough to facilitate mule deer movement and should be situated as far away from residential areas as possible.