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Exposure and Response of Morelet's Crocodile (Crocodylus moreletii) Populations to Endocrine Disrupting Compounds in Belize, Central AmericaEPA Grant Number: R826310
Title: Exposure and Response of Morelet's Crocodile (Crocodylus moreletii) Populations to Endocrine Disrupting Compounds in Belize, Central America
Investigators: McMurry, Scott T.
Current Investigators: McMurry, Scott T. , Anderson, Todd A.
Institution: Texas Tech University
EPA Project Officer: Turner, Vivian
Project Period: December 1, 1997 through November 30, 2000 (Extended to December 31, 2002)
Project Amount: $159,788
RFA: Endocrine Disruptors (1997) RFA Text | Recipients Lists
Research Category: Economics and Decision Sciences , Health , Safer Chemicals , Endocrine Disruptors
Much of the concern regarding endocrine disrupting compounds (EDCs) stems from data showing reproductive impairment and population declines of American alligators (Alligator mississippiensis) in Lake Apopka, Florida. The principal objective of this study is to examine exposure and response of another crocodilian, the endangered Morelet's crocodile (Crocodylus moreletii), to EDCs in Belize and assess the effect of these chemicals on crocodile populations. In a recent study, we found EDCs, including p,p -DDE, in Morelet's crocodile eggs from three lagoons in Belize. We now hypothesize that crocodiles inhabiting contaminated lagoons contain higher EDC concentrations in their tissues than individuals in non-contaminated areas, and that differences in crocodile morphology, blood hormone levels, serum chemistry, reproductive success, population density, and juvenile survival exist between contaminated and non-contaminated sites.
Blood, fat, non-viable eggs and population data will be collected (non-lethally) from crocodiles on contaminated and reference sites to examine exposure and effects of EDCs at the individual and population levels. To assess effects at the individual level, differences in biochemical (plasma testosterone, 17B-estradiol, vitellogenin, serum chemistry) and morphological (penis size) endpoints between contaminated and reference sites will be examined. Crocodile response to EDC exposure at the population level will be assessed by examining differences in endpoints of reproductive success (nesting success, clutch viability) and population structure (density, size structure, sex ratios, juvenile survivability) between contaminated and reference sites.
When completed, this research will provide much-needed information on the linkage between EDC exposure at the individual level and resulting effects at the population level. Comparison of these data with data from American alligators from Lake Apopka will provide a unique opportunity to examine whether Lake Apopka is a worst-case scenario or if similar reproductive problems and population declines occur in other crocodilian species exposed to EDCs. Moreover, this study will provide valuable insight into the efficacy of reptiles, particularly crocodilians, as sensitive indicators of environmental contamination and ecosystems potentially at risk. This information will be especially useful for ecological risk assessment in tropical countries where reptiles are abundant and regulations governing the use of chemicals, some of them EDCs, are underdeveloped or inadequately enforced.