SREL Reprint #2195
Radiographic Determination of Fecundity: is the Technique
Safe for Developing Turtle 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 {Fax: 803-557-7324; E-mail: Hinton@srel.edu]
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
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.
