A multi-scale evaluation of eastern hognose snake (Heterodon platirhinos) habitat selection at the northern extent of its range.

摘要

A complex interaction of biotic and abiotic variables structure landscapes into a hierarchal assemblage of habitats. Species respond to this environmental hierarchy by selecting habitat based upon a set of ecological variables occurring across a range of organizational levels. However, as the criteria for selection may be scale-dependent, it is vital to quantify the influence these variables have on species distribution at each spatial scale. Two years of telemetry data from 17 individuals were used to examine the multi-scale selection process in the northern population of Heterodon platirhinos on the New Boston Air Force Station in New Boston, New Hampshire. Thermal quality, habitat structure, prey availability, and predator avoidance were predicted to be the primary influential variables dictating the selective process in these ectothermic organisms, with the thermal environment being of particular importance. Statistical comparisons and modeling results revealed that snakes were selective at all three spatial scales, with thermal extremes and habitat cover being the dominant influential variables. At the landscape level, mixed forest maintaining environmental temperatures above thermal minima (7.0°C) were highly selected whereas at the home-range level, hemlock forests that did not exceed thermal maxima (40.5°C) were preferred. Overall optimal habitat was identified as having the following characteristics: 1) mixed and hemlock forests having continuous canopy and understory architecture interspersed with fine-scale openings 2) close proximity to wetlands 3) high density of leaf litter, debris, and rocks and 4) homogeneous surface temperatures within critical thermal limits. Together, this structural configuration likely maximizes thermoregulatory precision while still conferring the secondary biological needs of predator avoidance and suitable prey availability.