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

Jason P Ross,Michael J Dreslik,Robert D Bluett

doi:10.3390/d11080124

Jason P Ross, Michael J Dreslik + Show 1 more

Open Access

https://doi.org/10.3390/d11080124

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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.

Highlights

Animal movements reflect the influence of biotic and abiotic factors on space and habitat use [1,2].understanding movement patterns is an important consideration for determining spatial requirements and habitat management [3]
We examined the residual plot and histogram of the global model to check for patterns and normality
Our analysis showed summary movement rates of A. mutica can be divided into two principal components

Summary

Introduction

Animal movements reflect the influence of biotic and abiotic factors on space and habitat use [1,2]. Understanding movement patterns is an important consideration for determining spatial requirements and habitat management [3]. Animal movements fit into two temporal categories: Daily movements and long-term seasonal or annual movements [5]. The distance and frequency of daily movements are useful to describe activity, whereas movements over longer distances and periods indicate annual patterns or dispersal. Most daily animal movements occur inside a defined area that an animal uses to survive, reproduce, and acquire resources; this area is termed a home range [2,6,7]. For animals constrained to linear habitats such as rivers, a simple linear range is sometimes used [8]. Examining the size, shape, and structure of an animal’s home range can help answer biological questions [5]

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