Implications of Fine-Grained Habitat Fragmentation and Road Mortality for Jaguar Conservation in the Atlantic Forest, Brazil

Abstract

Jaguar (Panthera onca) populations in the Upper Paraná River, in the Brazilian Atlantic Forest region, live in a landscape that includes highly fragmented areas as well as relatively intact ones. We developed a model of jaguar habitat suitability in this region, and based on this habitat model, we developed a spatially structured metapopulation model of the jaguar populations in this area to analyze their viability, the potential impact of road mortality on the populations' persistence, and the interaction between road mortality and habitat fragmentation. In more highly fragmented populations, density of jaguars per unit area is lower and density of roads per jaguar is higher. The populations with the most fragmented habitat were predicted to have much lower persistence in the next 100 years when the model included no dispersal, indicating that the persistence of these populations are dependent to a large extent on dispersal from other populations. This, in turn, indicates that the interaction between road mortality and habitat fragmentation may lead to source-sink dynamics, whereby populations with highly fragmented habitat are maintained only by dispersal from populations with less fragmented habitat. This study demonstrates the utility of linking habitat and demographic models in assessing impacts on species living in fragmented landscapes.

Fig 1. Some important protected sites in the study area, along the upper and the lower Paraná River.

The inside frame indicates the location of the study.

Fig 2. Density dependence function used in this model (solid line) and its uncertainty limits used in the sensitivity analysis (dashed lines).

In all models, the proportion of females that are breeding is 50% when population size (N) is small relative to carrying capacity. At carrying capacity, the proportion breeding is 32.9% (which gives an eigenvalue of 1.0; see text for details). The percent breeding declines as N increases, dropping to zero when N = 1.5∙K (1.25 to 1.75 used in the sensitivity analysis).

Fig 3. Radio-collared female jaguar (Panthera onca) roadkill, Morro do Diabo State Park, Brazil.

Fig 4. Spatial structure of jaguar populations identified by the model in the upper Paraná region.

Lighter shading indicates greater habitat suitability as given in Figure A in S1 Appendix. The polygons outline the populations. The population numbers correspond to those in Table 1, and in Figs 5 and 6.

Fig 5. Impact of road mortality on jaguar population persistence: Number of years out of 100 that each population was extant, under no road mortality (0; light gray bars); estimated mortality (1x; dark gray bars); and twice the estimated mortality (2x; black bars).

Fig 6. Effect of dispersal on population persistence: Number of years out of 100 that each population was extant under estimated mortality.

For several populations, model with no dispersal (black bars) resulted in much lower persistence than model with dispersal (gray bars).