Organochlorine Pesticide Residues in Caudal Scutes of Belize Morelet’s Crocodiles (Crocodylus moreletii)


Historically, Belize has used large quantities of organochlorine (OC) pesticides for agriculture and disease-vector control, yet few tools exist for noninvasive assessment of OC contaminant loads in Belize wildlife. Crocodile caudal (tail) scutes are clipped as a marking technique in wildlife management programs and may also have utility as a minimally invasive, nonlethal technique to assess contaminant burden. We collected caudal scutes from 96 Morelet’s Crocodiles in Belize over 2 yr to analyze scute tissues for OCs and to compare the observed OC concentrations among different scute tissue (fat, cartilage, and muscle) and among crocodiles of different age classes, sexes, and collection locations. Organochlorines of the DDT-type subclass were detected in 72 of 96 crocodiles, with methoxychlor detected in all 72 scutes containing OCs and p,p-DDE, p,p’-DDT, and p,p-DDD detected in 54, 47, and 20 scute samples, respectively. Organochlorines were more-frequently detected in scutes of adult crocodiles, but methoxychlor was occasionally observed in juveniles at concentrations two orders of magnitude higher than observed in adults, suggesting maternal offload of methoxychlor to offspring, greater exposure through juvenile habitat and diet, or both. Organochlorines were detected in crocodiles from all sampling locations with more frequent and higher concentrations observed in crocodiles from lagoon habitats than from river habitats. This study demonstrates that scutes can be used as a nonlethal indicator of OCs present in Morelet’s Crocodiles, a finding which has applications for determining the trophic transfer of OC pesticides through tropical aquatic food webs and for estimating the continuing risk posed to crocodiles and other species by OC pesticides.



Organochlorine pesticides, Organochlorines, Belize, Crocoodylus moreletii, Morelet’s Crocodiles, Pesticide contamination, Methoxychlor


50 J. of Herpetology 552