Effects of a Landscape Disturbance on the Habitat Use and Behavior of the Black Racer
The effects of disturbance, including prescribed fire, vary among species and their ability to adjust to the altered environment. Our objective was to link fire-caused habitat changes with shifts in habitat use and behavioral changes in the Southern Black Racer (Coluber constrictor priapus). We compared habitat availability between burned (experimental) and unburned (control) plots and used radio telemetry to evaluate snake behavior and habitat use. The numerical abundance of C. constrictor in burned habitat was nearly twice that in the control. In both treatments, C. constrictor was associated with areas that were more open, had less canopy cover, more new vegetative growth, and less, shallower leaf litter. However, the availability of these habitats was greater in the burn treatment. Snakes were more surface active in the burn treatment and tended to be more arboreal in the control treatment. Differences in available habitat may have caused an increase in surface activity in the burn treatment, which could have biased detection rates and created higher apparent abundance in the burned treatment. Females moved more often in the control treatment, which may be due to a lack of preferred thermal habitat and reproductive thermoregulatory demands. Ultimately, fire changed habitat availability and altered the movement rates and behavior of C. constrictor causing ecological effects that may not be detected when researchers only compare abundance.
Map of the study area (data available from the U.S. Geological Survey). The burn treatment is highlighted in red with the control treatment to the east. Boxes refer to study plots and a drift fence is located at the exact center of each plot. The brown lines represent dirt/gravel roads.
Size distribution of burn and control C. constrictor. The number of individuals captured in burn (black) and control (gray) treatments are sorted into 200 mm interval bins for snout–vent length (SVL). Despite more C. constrictor in the burn treatment, the size distributions in both treatments were similar.
Comparison of available habitat characteristics in burn and control treatments. Characteristics of available habitat in the burn (black) treatment were more associated with habitat variables toward the top of the ordination, and available habitat in the control (blue) treatment were more associated with habitat variables toward the bottom of the ordination. Hulls (dashed lines) represent the amount of variation associated with each treatment and 95% CI ellipses (solid lines) represent ordination area likely associated with true population mean. Crosses represent habitat variables correlated with ordination plot. CWD = coarse woody debris, Fewer.OST = fewer overstory trees, Fewer.UST = fewer understory trees, Litter.Depth = leaf litter depth, and TempA and TempG = air and ground temperatures, respectively.
Comparison of habitat use of C. constrictor and available habitat within each treatment. Habitat used by snakes in each treatment differed from available habitat characteristics for each treatment and available habitat differed between treatments. Characteristics of available habitat (dashed lines) and habitat used by C. constrictor (solid lines) in burn (black hulls and ellipses) and control (blue hulls and ellipses) treatments. Hulls represent variation of each group and ellipses (smaller, filled polygons) represent 95% CI. Non-overlap between ellipses suggests significant differences. Habitat characteristic codes are the same as Figure 3.
Snakes used habitat (unshaded bars) that contained a greater percentage of grasses (A), forbs (B), and woody plants (C) than what was available (shaded bars) within burn and control treatments. Comparisons show means±2SE.
Snakes used habitat (unshaded bars) that contained less canopy cover (A), less leaf litter (B), and were greater distances to overstory trees (OST; C) than what was available (shaded bars) within burn and control treatments. Comparisons show means±2SE.
Comparison of behaviors exhibited by C. constrictor in burn and control treatments. Snakes were surface active more in the burn treatment and arboreal or under structure more in the control treatment.
Movement rates differed between treatments but were dependent upon sex. Males moved more than females in the burn treatment, and females moved more than males in the control treatment. Male movement rates did not appear to differ between treatment. Comparisons show means±2SE.
Contributor Notes
Associate Editor: J. W. Snodgrass.