Abundance and Population Structure of Eastern Worm Snakes in Forest Stands with Varous Levels of Overstory Tree Retention

In-depth analyses of a species’ response to canopy retention treatments can provide insight into reasons for observed changes in abundance. The eastern worm snake (Carphophis amoenus amoenus Say) is common in many eastern deciduous forests, yet little is known about the ecology of the species in managed forests. We examined the relationship between silvicultural techniques, particularly shelterwood cuts with varying levels of basal area retention, and the abundance and population structure of eastern worm snakes in the Cumberland Plateau of northern Alabama. Treatments included fi ve levels of basal area retention at 15 units (4 ha/unit): 0, 25, 50, 75 percent retention, and control (100 percent retention) with three replicates each. Drift fences and coverboards were used to sample worm snake populations in each treatment. Worm snake abundance did not vary among treatments. Sex ratios were skewed towards males on clearcut treatments. The percentage of females in gravid condition did not differ among treatments, and the percentage of the sample comprised of juveniles was consistently high and also did not vary among treatments. Male worm snakes were more massive at a given length in controls than 25 percent retention treatments. Mass to length ratio increased linearly with increasing basal area for males. Our results highlight the subtle changes that these treatments exerted on eastern worm snakes. 1Graduate student, and associate professor, Center for Forestry and Ecology, Alabama A&M University, Normal, AL; Research Forester, USDA Forest Service, Southern Research Station, Alabama A&M University, Normal, AL, respectively. Citation for proceedings: Stanturf, John A., ed. 2010. Proceedings of the 14th biennial southern silvicultural research conference. Gen. Tech. Rep. SRS-121. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 614 p. INTRODUCTION The eastern worm snake (Carphophis ameonus. amoenus Say) is a secretive, small (< 30 cm total length), fossorial snake that is distributed from southern NY and MA south to northern AL, GA, and SC (Conant and Collins 1991). In AL the species inhabits a variety of habitats, and is a common forest fl oor inhabitant of mesophytic forests (Mount 1975). Although the species can reach high densities relative to other reptile species in optimal habitat (Ernst and Barbour 1989), there are few detailed ecological studies of the species, especially on the effects of canopy removal. Work by Russell and Hanlin (1999) showed that this species reaches high abundances adjacent to small isolated wetlands in the Coastal Plain of SC. In KY, the species was studied using radioisotope tags and found to have small home ranges (23 to 486 m2) (Barbour and others 1969). The objectives of this study were to compare the abundance, demographics, population structure, and body size of eastern worm snakes across fi ve levels of overstory tree retention in northern AL. In doing so we tested the following four hypotheses: H1o: Relative abundance of worm snakes will not vary by canopy retention treatment H2o: Sex ratio, percentage of population comprised of gravid females and juveniles will not vary by treatment H3o: Body size distribution will not vary by treatment H4o: Ratio of mass: length will not vary by treatment STUDY AREA The study took place in the Cumberland Plateau region of Jackson County, which is located in northeastern AL. Study sites are upland forests dominated by oaks (Quercus spp.), hickories (Carya spp.), yellow-poplar (Liriodendron tulipifera L.) and sugar maple (Acer saccharum Marsh.). Soils are composed of gravelly and stony loams, and slopes average between 12 and 20 percent. The study followed a randomized complete block design with three blocked replicates of fi ve treatments involving varying levels of basal area retention of trees. Treatment categories included clearcuts, 25, 50, and 75 percent retention, and controls. The clearcuts, 25, and 50 percent retention treatments were chainsaw-felled in a commercial logging operation. In 75 percent retention treatment units, the midstory was removed by incising trees and applying the herbicide Arsenal® (active ingredient imazapyr, BASF Corp., Ludwigshafen, Germany) into the cut area to achieve a shelterwood cut. Two blocks were located on a north-facing slope at Jack Gap, and the other at Miller Mountain on a southwest-facing slope. Individual experimental units were 4-ha in size.