SREL Reprint #2195

Radiographic determination of fecundity: Is the technique safe for developing embryos?

Thomas G. Hinton1, Peter D. Fledderman2, Jeffrey E. Lovich3, Justin D. Congdon1, and J. Whitfield Gibbons1

1Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802 USA
2Westinghouse Savannah River Company, Aiken, South Carolina 29802 USA
3U.S Geological Survey, Palm Springs Field Station, 63500 Garnet Avenue, North Palm Springs, California 92258 USA

Introduction: Conservation biology requires thorough knowledge of an animal's life history characteristics, as do scientifically sound ecological risk assessments. Successful management of endangered species, or determination of effects from human impacts, is difficult without fundamental demographic data. Data such as prolonged decreased fecundity, for example, can be a foreboding endpoint indicative of declining populations. Obtaining adequate samples to detect changes in fecundity, however, is a challenging task for the research biologist. Herpetologists have largely overcome the problem in the study of oviparous species by using radiography as a tool to obtain critical reproductive information. Radiographs disclose the number of eggs in the oviducts (Fig. 1). Such information is important when predicting ecological effects or examining long-term demographic trends. In addition to clutch size, information about reproductive frequency, age at sexual maturity, and egg size can be gleaned — if not totally, at least in part — from radiographs. Despite the slight enlargement of actual egg dimensions (Graham and Petokas, 1989), egg widths taken from radiographs are strongly correlated with egg wet mass, dry mass, lipid content, and size of hatchling (Congdon et al., 1983). Radiographs have provided key data on how life history characteristics may constrain population responses, information that has implications for conservation and management of long-lived organisms (Congdon et al., 1993, 1994).

SREL Reprint #2195

Hinton, T.G., P. Fledderman, J. Lovich, J.D. Congdon, and J.W. Gibbons. 1997. Radiographic determination of fecundity: Is the technique safe for developing embryos? Chelonian Conservation and Biology 2:409-414.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).