Growth and Sexual Dimorphism of Gopherus Polyphemus in Central Florida

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gopher tortoise, growth, ontogeny, sexual dimorphism, Florida, fire ecology, sandhill


Using data from gopher tortoises captured over a 10-yr period in a population in central Florida, we modeled growth patterns and analyzed morphological characters for sexual dimorphism. Growth rates of non-adults were rapid and facilitated the attainment of sexual maturity at a relatively young age for females (9-11 yr) and probably for males as well. Rapid growth of tortoises at our study site likely is a response to the length of the growing season and/or high quality habitat, maintained by periodic controlled burning. The degree of sexual dimorphism was low in our population perhaps because of rapid growth and the relatively early attainment of sexual maturity. The best external morphological indicator of the sex of an individual was the size, shape, and depth of the plastral concavity. Anal width and anal notch also were dimorphic but did not become distinctly dimorphic until sexual maturity was attained, and by then, the plastral concavity could be used to distinguish sex. Because female tortoises mature only a year or so after male tortoises, morphological characteristics associated with differences in body size between the sexes (e.g., body width and body thickness) do not have sufficient time to become distinct. We suggest that rapid growth and an abrupt attainment of sexual maturity diminish sexual dimorphism in our population in central Florida. Perhaps the most significant result of this research was to re-emphasize the value of active habitat management (periodic burning) to resident tortoises.

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Citation / Publisher Attribution

Herpetologica, v. 50, no. 2, p. 119-128