Movement and Home Range of the Smooth Softshell Turtle (Apalone mutica): Spatial Ecology of a River Specialist

Abstract

Spatial ecological information is necessary to guide the conservation efforts of river turtles, but it is lacking for many species including the smooth softshell turtle (Apalone mutica). We investigated the spatial ecology of A. mutica in two reaches of the Kaskaskia River in Illinois, USA to determine variables influencing movement rates, the best estimate of home range, and variables influencing home range size. We radio-tracked 28 A. mutica from 2013 to 2014 and used an information theoretic approach to select the best models describing movement and home range estimates. Mean movement rate was 142.3 m/day and was highly variable with some movements >2 km/day. Movement peaked at moderate water temperatures early in the active season, increased at higher water levels for females, and was greater in the higher stream order. The sexes responded differently to environmental variation, with female movement higher in most but not all conditions. The most informative home range estimate was a 95% kernel density estimate using likelihood cross-validation (CVh) smoothing clipped to the river channel. The mean home range size was 18.1 hectares and increased with movement rate, number of radio-locations, and stream order. Most turtles had well-defined home ranges, though a few were possibly nomadic. Our methods also provide a framework for spatial ecological studies of other riverine species.

Movement and Home Range of Amur Soft-Shell Turtle (Pelodiscus maackii) in the Ussuri River, Heilongjiang Province, China

“…The telemetry data acquired for adult ASTs indicated that they did not restrict their range to shallow, nearshore areas with abundant vegetation or to water channels. The daily movement rates of adult ASTs observed in our study were similar to those documented for adult smooth soft-shell turtles (Apalone mutica) in the Kaskaskia River in Illinois, North America [41]. However, this previous study did not include subadults; therefore, we could not make a relevant comparison.…”

“…The mixed-effects model showed a significant positive correlation between water temperature and the daily movement rate. We observed no discernible peak in the movement rate at intermediate temperatures, which was followed by a decline as the temperature increased further [41,53,54]. This may have been attributed to the relatively low water temperatures in the study area, which is characterized by a temperate climate.…”

“…Among the eight subadult ASTs for which we estimated a complete home range size in the study area, the individual LRs exhibited considerable variability, ranging from 388 to 1145 m. This notable divergence in LRs between individuals has also been observed in other soft-shell turtle species [40,41]. The MCP estimator yields values ranged from 1.30 to 3.65 ha.…”

Evaluating translocation success of wild eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) in Blue Ridge Ecoregion streams using pre- and post-translocation home range sizes and movement metrics

“…MCPs were calculated as convex hulls that contained all locations [ 59 ], using the minimum bounding geometry tool in ArcGIS Pro (2.5.0, Esri, Redlands, CA). These MCPs were clipped to exclude areas outside the stream, using similar methodology to Ross et al [ 60 ].…”

Advances in the Biology and Conservation of Turtles

“…These units offer tremendous advantages over current tracking methods, including high-resolution location data. Ross et al [11] coupled standard VHS-based radio tracking data with an information theoretic analytical approach to select the best home range models, thus indicating a practical methodology for choosing among the many home range methodologies that have been variously applied to turtles over many decades. Habeck et al [12] similarly evaluated home range estimates, in this case taking advantage of the many studies of box turtle (Terrapene carolina and T. ornata) home ranges.…”