Modeling the effects of deforestation on the connectivity of jaguar Panthera onca populations at the southern extent of the speciesí range

Abstract

We employed least-cost and circuit theory modeling to model the connectivity among previously defined Jaguar Conservation Units (JCUs) at the southern limit of the jaguarís range in Argentina, Bolivia, Brazil and Paraguay, in order to assess the effects of deforestation and land use change between 2000 and 2014. Due to uncertainty about possible limitations to jaguar dispersal, we examined connectivity where linkages were not cost-limited and limited to 1000 km cost-weighted distance. When linkage length was not cost-limited, total linkage area decreased by 9%, and mean least-cost distance and mean effective resistance increased by 6 and 31%, respectively, from 2000 to 2014. Limiting linkages to 1000 km cost-weighted distance indicated that the southern- and eastern-most JCUs were isolated as early as 2000 and that the number of linkages between the other JCUs decreased between 2000 and 2014, causing the linkage area to decrease by 27% while the least-cost distance of the remaining linkages increased by a mean of 4% and effective resistance increased on average by 44%. By limiting linkages to a plausible cost-weighted distance, we demonstrated that JCUs in the Atlantic Forest, Argentine Chaco and the Argentine/Bolivian Yungas have been isolated since at least 2000, and that there has been a loss of connectivity through eastern Bolivia, increased resistance in the remaining linkages and a constriction of all but one linkage to a minimum width of <8 km. Our results are consistent with an observed loss of genetic diversity in jaguar populations within portions of our study area and indicate a need for further research to better quantify jaguar dispersal.