A Surfeit of Studies: What Have We Learned from All the Box Turtle ( Terrapene carolina and T. ornata ) Home Range Studies?

Home range (HR) studies are a particularly common approach to investigations of animal habitat use, resource availability, and response to management manipulation such as relocations. <i>Terrapene carolina</i> (Eastern box turtle) and its sister taxon <i>T. ornata</i> (Ornate box turtle) are especially popular subjects of HR studies because they are relatively easily tracked. <i>Terrapene</i> HR studies have revealed a wide variation in HR sizes within and between populations, due to factors such as differences in ecoregion and analytical approach (e.g., minimum convex polygons, kernel analysis, bivariate normal, multivariate Ornstein&#8722;Uhlenbeck stochastic process, harmonic means). We performed a meta-analysis of the available literature, including unpublished work to avoid bias due to under-publication, to explore the causes for variation in HR size. We found 19 studies reporting <i>T. carolina</i> HR sizes and seven studies reporting <i>T. ornata</i> HR sizes; the resulting meta-analysis revealed patterns that are not visible in the individual studies. We found important differences between the species: female <i>T. ornata</i> had smaller HRs than males, whereas the opposite is true for <i>T. carolina</i>, and <i>T. ornata</i> HRs were influenced by ecoregion, while <i>T. carolina</i> HRs were not similarly influenced. Not surprisingly, we found that choice of analysis technique affected HR estimate; analyses using ellipses resulted in larger HR estimates than all the other techniques, while kernels were smaller than minimum convex polygons. Although not indicated by individual studies, our meta-analysis showed that the HRs of relocated <i>T. carolina</i> females were significantly larger than those of non-relocated females. Although the number of individual turtles in studies varied from three to 25, the sample size did not significantly affect HR size.

Abstract licence: CC BY

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