Spatial Ecology and Multi-scale Habitat Selection by a Threatened Rattlesnake: The Eastern Massasauga (Sistrurus Catenatus Catenatus)

Abstract

Using radio telemetry and geographic information systems (GIS), we investigated movement patterns, home ranges, and habitat selection by Eastern Massasauga rattlesnakes from 2003 to 2004 at an 815-ha fen preserve located in southeastern Michigan, USA. We tested habitat selection on three different scales: microhabitat (by modeling differences in climatic and structural variables between snake-selected sites and random sites, using logistic regression), macrohabitat, and landscape-scale (both by compositional analysis comparing proportions of habitat types used versus proportions available). One hundred percent minimum convex polygon (MCP) home ranges averaged 1.3 ha, and daily movement rates averaged 6.9 m/d. Models predicted that snakes exhibit complex microhabitat selection based on multiple climatic and structural variables including soil temperatures, relative humidity, canopy cover, litter depth, and various vegetation parameters. Snakes actively establish home ranges in the broader landscape by selecting areas with disproportionate quantities of emergent wetland, scrub/shrub wetland, and lowland hardwood habitats. Upland hardwood and all human-altered landscapes were rarely used, even though they were available. This has potentially serious conservation implications. Encroachment of these types of landscapes into areas of suitable habitat could severely restrict movement and home range sizes of these snakes. Potential disruption of movement patterns and gene flow of remaining populations could be extremely detrimental to this species.