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Morelet's crocodile (Crocodylus moreletii) and hybrid crocodiles (C. moreletii × acutus) are mound-nesting crocodilians found in the lowlands of northern and southern Belize, respectively. Nests of both crocodilians consist of large mounds of soil, vegetation, leaf litter, and in some cases sand. We here report on the fauna associated with nest mounds of C. moreletii and C. moreletii × acutus, and describe the associations between crocodiles and commensal fauna. Our data were collected during various ecological studies conducted from 1992 through 2000, and we examined 138 active (containing eggs) nests of C. moreletii and 11 active nests of C. moreletii × acutus. We noted the occurrence of at least 14 species of fauna associated with 45 (32.6%) C. moreletii and three (27.2%) C. moreletii × acutus nests. Nest-associated fauna included ants, bees, termites, turtles, squamates, birds, and mammals. Associations included five species dwelling within crocodile nest mounds, four species that deposited eggs in crocodile nest mounds, and five species nesting in close proximity to crocodile nests. Nest-associated fauna presumably benefit from the protection afforded by nest attendance and aggressive defence behaviour of female crocodiles, although these benefits have yet to be empirically established. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Body condition factors have been used as an indicator of health and well-being of crocodilians. We evaluated body condition of Morelet's Crocodiles (Crocodylus moreletii) in northern Belize in relation to biotic (size, sex, and habitat) and abiotic (location, water level, and air temperature) factors. We also tested the hypothesis that high water levels and warm temperatures combine or interact to result in a decrease in body condition. Size class, temperature, and water level explained 20% of the variability in condition of Morelet's Crocodiles in this study. We found that adult crocodiles had higher condition scores than juveniles/subadults but that sex, habitat, and site had no effect. We confirmed our hypothesis that warm temperatures and high water levels interact to decrease body condition. We related body condition of Morelet's Crocodiles to natural fluctuations in air temperatures and water levels in northern Belize, providing baseline conditions for population and ecosystem monitoring. [ABSTRACT FROM AUTHOR]

Abstract: Seven complete clutches of Morelet''s crocodile (Crocodylus moreletii) eggs were collected in northern Belize and examined for organochlorine (OC) pesticide residues. The primary OC detected, p,p-DDE, was found in every egg analyzed (n =175). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, aldrin, and endosulfan I. Concentrations of individual OCs ranged from 4ppb (ng chemical/g egg wet weight) to greater than 500ppb. A statistical evaluation of p,p-DDE levels in three complete clutches was used to derive the minimum number of eggs needed from a clutch to precisely determine the mean p,p-DDE concentration representative of that clutch. Sample sizes of 8 (80% confidence level) and 11 (90% confidence level) were determined to yield an accurate estimate of contaminant levels in a full clutch of eggs. The statistically recommended sample size of 11 eggs (at 90% confidence level) was successfully tested on the four additional clutches. [Copyright &y& Elsevier]

Microsatellite data were generated from hatchlings collected from ten nests of Morelet's Crocodile (Crocodylus moreletii) from New River Lagoon and Gold Button Lagoon in Belize to test for evidence of multiple paternity. Nine microsatellite loci were genotyped for 188 individuals from the 10 nests, alongside 42 nonhatchlings from Gold Button Lagoon. Then mitochondrial control region sequences were generated for the nonhatchlings and for one individual from each nest to test for presence of C. acutus-like haplotypes. Analyses of five of the nine microsatellite loci revealed evidence that progeny from five of the ten nests were sired by at least two males. These data suggest the presence of multiple paternity as a mating strategy in the true crocodiles. This information may be useful in the application of conservation and management techniques to the 12 species in this genus, most of which are threatened or endangered.

Vitellogenin induction has been widely used as a biomarker of endocrine disruption in wildlife, but few studies have investigated its use in wild reptiles living in contaminated habitats. This study examined vitellogenin induction in Morelet's crocodiles (Crocodylus moreletii) from wetlands in northern Belize contaminated with organochlorine (OC) pesticides. Vitellogenin was measured in 381 crocodile plasma samples using a vitellogenin ELISA previously developed for this species. Vitellogenin was detected in nine samples, all from adult females sampled during the breeding season. Males and juvenile females did not contain detectable levels of vitellogenin; however, many of these animals contained OC pesticides in their caudal scutes, confirming contaminant exposure. The lack of a vitellogenic response in these animals may be attributable to several factors related to the timing and magnitude of exposure to endocrine-disrupting chemicals and should not be interpreted as an absence of other contaminant-induced biological responses.

Despite high animal diversity in the Neotropics and the largely unregulated use and disposal of pesticides and industrial chemicals in Central America, few data exist regarding accumulation of environmental contaminants in Central American wildlife. In this study we examined accumulation of metals and organochlorine (OC) pesticides in caudal scutes of crocodiles from Belize and Costa Rica. Scutes from Morelet's crocodiles (Crocodylus moreletii) from two sites in northern Belize were analyzed for metals, and scutes from American crocodiles (C. acutus) from one site in Costa Rica were analyzed for metals and OC pesticides. All scutes (n=25; one scute from each of 25 individuals) contained multiple contaminants. Mercury was the predominant metal detected, occurring in all scutes examined from both species. Other metals detected include cadmium, copper, lead, and zinc. American crocodile scutes from Costa Rica contained multiple OC pesticides, including endrin, methoxychlor, p,p'-DDE, and p,p'-DDT, all of which occurred in 100% of scutes analyzed (n=6). Mean metal and OC concentrations varied in relation to those previously reported in crocodilian scutes from other localities in North, Central, and South America. OC concentrations in American crocodile scutes were generally higher than those previously reported for other Costa Rican wildlife. Currently, caudal scutes may serve as general, non-lethal indicators of contaminant accumulation in crocodilians and their areas of occurrence. However, a better understanding of the relationships between pollutant concentrations in scutes, internal tissues, and environmental matrices at sample collection sites are needed to improve the utility of scutes in future ecotoxicological investigations.

Recent studies examined the utility of the chorioallantoic membrane (CAM) as a nonlethal, noninvasive indicator of environmental contaminant exposure in oviparous wildlife. The CAM is a highly vascularized extraembryonic membrane that functions as a site for respiration, nutrient transport, and waste storage during embryonic development. After hatching, the CAM is usually discarded with the eggshell and can be used for chemical residue analysis. Chorioallantoic membranes have been used successfully to examine contaminant exposure and predict chemical concentrations in multiple species of birds and reptiles. In this study, we examined organochlorine (OC) pesticide concentrations in CAMs from eggs of Morelet's crocodiles (Crocodylus moreletii) from northern Belize. Multiple OCs were detected in crocodile CAMs, including aldrin, dieldrin, endrin, dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethane, dichlorodiphenyldichloroethylene (DDE), heptachlor, lindane, and methoxychlor. Number and concentrations of OC compounds in CAMs were variable. The most prevalent contaminant detected was DDE, which occurred in 69% of CAMs, with concentrations ranging from 0.3 parts per billion (ppb) to 17.0 ppb. The OC burdens in crocodile CAMs confirm contamination of eggs and suggest exposure in embryos and maternal females. These results further support the use of CAMs as qualitative indicators of OC exposure in oviparous wildlife. The efficacy of this sampling technique in the field will depend on the logistics and cost associated with CAM collection and the specific life history traits of the wildlife species.