Grantee Research Project Results

Potential Consequences of Among and Within Population Variation in Diet Composition of Pigmy Rattlesnakes (Sistrurus miliarius) in Central Florida: A Dietary Analysis Using Stable Isotope Technology

EPA Grant Number: U916160
Title: Potential Consequences of Among and Within Population Variation in Diet Composition of Pigmy Rattlesnakes (Sistrurus miliarius) in Central Florida: A Dietary Analysis Using Stable Isotope Technology
Investigators: Pilgrim, Melissa A.
Institution: University of Arkansas
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $111,608
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Fellowship - Terrestrial Ecology , Academic Fellowships , Ecological Indicators/Assessment/Restoration

Objective:

The objective of this research project is to conduct a study that uses stable isotope analyses to investigate variation in diet among three populations of pigmy rattlesnakes (Sistrurus miliarius) in central Florida, along the floodplains of the St. John's River. Local variation in diet can have profound effects on bioenergetics, life history, and population dynamics. Mark-recapture analyses have revealed among-population variation in demographic and life history characteristics, even though the populations are separated by less than 4 km. My research evaluates the effect of diet composition on rattlesnake demography and life history.

Approach:

I am creating carbon ( delta ¹³C) and nitrogen ( delta ¹⁵N) isotope profiles of potential prey items available to the rattlesnakes in each population. I have determined that the isotope composition ( delta ¹³C and delta ¹⁵N) of snake scale tissue reflects snake diet. I am determining the isotope composition of scale samples collected from snakes within each population. By matching isotope ratios of scale samples with isotope ratios of prey items, I am determining the diet composition of individual snakes within each population. Recaptures of individuals and analysis of among-segment variation in isotope ratios of individual rattles are allowing me to assess individual variation in diet. By integrating mark-recapture data sets with isotope data sets, I will correlate among-population variation in diet with among-population variation in demographic and life history characteristics. In addition, I am evaluating the energetic quality of snake prey items and investigating the effect of prey type on rattlesnake digestive efficiency. The energetic work and the digestive physiology information will provide insight into mechanisms underlying any correlation among snake isotope ratios and life history variation. Collectively, my research tests the hypothesis that life history and demographic variation observed among the three rattlesnake populations can be explained by population-specific diets.

Supplemental Keywords:

fellowship, pigmy rattlesnakes, Sistrurus miliarius, isotope analysis, diet composition, snake scales, stable isotope technology, mark-recapture analysis.

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.