As habitats become increasingly fragmented by natural and anthropogenic disturbances, the issue of how predation risk affects the ability of animals to move among habitat patches becomes more important. Animals come into contact with a variety of structural components when moving through a landscape. The response of animals to these components should be dictated by the costs and benefits that each poses to movement. Factors that alter the relative costs and benefits associated with landscape structure are therefore likely to influence animal movement, and connectivity within a habitat. Using a beach mouse (Peromyscus polionotus leucocephalus), we evaluate the relative importance of gap width, patch quality and landscape context to gap crossing probability under different levels of predation risk. P. p. leucocephalus nests on coastal dune fragments surrounded by a matrix of open sand and sparse vegetation, which allowed observation of nightly foraging paths across the sand in new and full moon periods. Altered movement between moon phases was assumed to result from differences in perceived predation risk as illumination levels changed. For each gap crossed by a foraging path we recorded gap width, the quality of target resource patches, and the landscape context of each target patch. Measures of target patch quality included size, vegetation cover and height, food plant richness, and height of accumulated sand. The landscape context of target patches was recorded as the distance from nest sites in dune fragments, distance from wetland habitat, distance from high tide line and amount of dune habitat nearby.
Results/Conclusions
Classification tree analysis revealed that predation risk was a key factor influencing both gap crossing probability and the relative importance of other landscape features to gap crossing probability. Gap width and patch quality measures were unimportant to gap crossing probability during full moon periods, but became important during new moon periods. Gap width was of greater importance to gap crossing probability than most measures of target patch quality in new moon periods, underscoring the importance of movement costs in hurricane impacted habitats. Accumulated sand height of target patches became more important as gap width increased. This pattern suggests that beach mouse perception of remote patches may be important to connectivity, or that beach mice balance patch quality against movement cost. Target patch size and vegetation cover were weak indicators of gap crossing probability. These results indicate that variation in predation risk may alter the relative importance of landscape features to habitat connectivity.
