Landscape Ecology of the Eastern Massasauga (Sistrurus catenatus)
Habitat fragmentation and alteration are considerable impediments in conservation biology. These phenomena impact the quality of habitat for wildlife species, as well as access to different habitats for behaviors such as foraging, hunting and mating. Habitat destruction is the leading cause of species extinction and population declines around the world. Habitat destruction, a product of human development comes in many forms. Minor alterations in landscapes can have wide-ranging effects on the quality and connectivity of habitats, such as altering hydrological processes, fire regimes, nutrients cycling, increases habitat fragmentation, and decreases in gene flow. For the Eastern Massasauga (Sistrurus catenatus), habitat alteration and fragmentation can impact population dynamics substantially. The quality and variability of habitat available to the species are crucial, as the Eastern Massasaugas requires basking sites, refugia, overwintering sites, etc. To examine the quality and connectivity of habitat within our study site, we radio-tracked wild-caught Eastern Massasaugas during the active season (May to mid-August) over the duration of five years. In Chapter 2, we then used these radio-tracking events to examine the roles that the landscape scale play in habitat suitability and from there modeled for suitable habitat. Our study site is composed of shrub-scrub wetlands and Northern hardwood forests, with parts of the landscape altered as a result of mowing, cutting and burning. The habitats are highly variable, increasing the need for habitat modeling to assess habitat suitability at multiple landscape levels. In Chapter 3, we also used these radio-tracking events to examine the permeability of manmade landscape features within the study site, including roads and trails, to determine how these structures impact movement and thus habitat connectivity. We also assessed how different attributes of roads and trails impact permeability. Our findings suggest that modeling for and preservation of the different types of habitats necessary for survival is crucial. This includes active season habitat, particularly open canopy basking habitat close to hibernacula for gravid females. Overwintering habitat is also crucial and is generally characterized by water tables that are at or very near the surface. Our findings also suggest that overwintering habitat might be degraded by habitat succession and augmented by disturbance, fire in particular. As overwintering habitats appear to be especially limited and are believed to be crucial to the continued success of Eastern Massasaugas, preservation of this habitat is particularly vital. We have also found that our study site is substantially fragmented by roads and that though corridors do exist within the landscape, these corridors might be short-lived, suggesting a need for the installation of culverts to facilitate dispersal and active season movement.
Kingsbury, Purdue University.
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