Animal Dispersal in Fragmented Habitat: Measuring Habitat Connectivity, Corridor Use, and Dispersal Mortality

Abstract

We used a spatially explicit dispersal simulation to generate movement frequencies and distances for comparison with real dispersal frequencies collected in the field from two habitat-specific, sedentary bird species. The relationship between these two data sets allowed us to (1) test the hypothesis that the study species used corridor routes during dispersal; (2) measure the degree of reliance on corridor continuity; (3) estimate the rate of dispersal mortality with respect to distance traveled, and (4) give examples of how the model can be used to assess habitat connectivity with respect to similarly behaved species. We found that Blue-breasted Fairy-wrens and White-browed Babblers both used corridor routes during dispersal. Blue-breasted Fairy-wrens were inhibited by gaps greater than about 60 m, whereas White-browed Babblers crossed gaps of at least 270 m wide. For each species, the rate of dispersal mortality per unit distance traveled was about the same. Because we have effectively partitioned the risk of dispersal mortality from the chance of outside dispersal, and because our mortality estimates are model dependent but landscape independent, they can be transported to other landscapes on which simulations have been run and, therefore, can be used in population viability assessment of unstudied or hypothetical animal populations.

Keywords

• animal dispersal
• Blue-breasted Fairy-wren
• dispersal model
• dispersal mortality
• fragmentation
• habitat connectivity
• <i>Malurus pulcherrimus</i>
• <i>Pomatostomus superciliosus</i>
• spatially explicit dispersal
• vegetation corridors
• White-browed Babbler.