Ecology of mammalian predators in a fragmented landscape

Thomas Michael Gehring, Purdue University

Abstract

I examined the effects of agriculturally induced fragmentation of habitat on the spatial distribution of a guild of mammalian predators, the relative risk of predation for nests of ground-nesting birds, and the spatial ecology of long-tailed weasels (Mustela frenata). I developed predictive models for specific mammalian predators based on local habitat characteristics, element- and landscape-level attributes. My results suggest that mammalian predators view landscape fragmentation at different spatial scales and demonstrate strong interspecific differences in their response to spatial elements. These differences appear to be related to variation in mobility and predation risk (which are correlated with body size) and niche breadth exhibited by predator species. I also developed models to assess the probability of nest predation based on egg size, type of predator, local habitat attributes, and element- and landscape-level variables. The differential responses of nest predators to landscape structure appear to explain much of the variation in the spatial distribution and intensity of nest predation in a landscape. However, egg size and the type of predator also are important determinants of nest fate. Greater rates of nest predation corresponded with greater intensity of use of spatial elements by small mammals and mesopredators for travel, shelter, and foraging patches. Lower nest predation rates in fields were linked to the behavioral avoidance of this element by raccoons and opossums, perhaps in response to the perceived predation risk from coyotes. In a radio-telemetry study of long-tailed weasels, I found that weasels exhibited differential patterns of habitat selection, and these patterns were dependent on spatial scale. Weasels selected forest patches, fencerows and drainage ditches, whereas agricultural fields were avoided. Forest patches and fencerows provided suitable den sites in close proximity to an abundant and diverse prey community. On the other hand, drainage ditches provided movement corridors and free-standing water for long-tailed weasels. Long-tailed weasels appear to be sensitive to agriculturally induced habitat fragmentation as evidenced by their habitat selection patterns and limited dispersal ability. I discuss the relevance of my findings for defining ecological landscapes, understanding predator-prey interactions at multiple spatial scales, and conserving predator and prey populations in fragmented landscapes.

Degree

Ph.D.

Advisors

Swihart, Purdue University.

Subject Area

Forestry|Ecology

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