Steven G. Platt

Organochlorine contaminants in Morelet's crocodile (Crocodylus moreletii) eggs from Belize

Non-viable eggs of Morelets crocodile (Crocodylus moreletii) were collected from Gold Button (GBL) and New River lagoons (NRL) in northern Belize and screened for organochlorine (OC) compounds using gas chromatography (GC) with electron capture detection (ECD). All egg samples from both lagoons (n = 24) tested positive for one or more OCs. Primary contaminants were p,p-DDE and methoxychlor, detected in 100% and 29% of the eggs examined, respectively. Concentrations of individual OC contaminants ranged from 1 ppb (ng chemical/g egg) to > 0.5 ppm (microgram chemical/g egg). Total concentrations of OCs (sum of all OCs) for one egg collected from a nest at GBL reached as high as 0.7 ppm. Sediment samples from both lagoons also tested positive for OCs (lindane, aldrin, methoxychlor, heptachlor epoxide, p,p-DDT, among others). Nest media (soil and plant material) collected from crocodile nests at GBL were positive for p,p-DDT, methoxychlor, aldrin, endosulfan II, and endrin aldehyde. Based on the 24 egg samples analyzed to date, crocodiles from both lagoons are being exposed to OCs. Such exposure may present a health threat to populations of crocodiles in Central America.

Low levels of nucleotide diversity in Crocodylus moreletii and evidence of hybridization with C. acutus

Examinations of both population genetic structure and the processes that lead to such structure in crocodilians have been initiated in several species in response to a call by the IUCN Crocodile Specialist Group. A recent study used microsatellite markers to characterize Morelets crocodile (Crocodylus moreletii) populations in north-central Belize and presented evidence for isolation by distance. To further investigate this hypothesis, we sequenced a portion of the mitochondrial control region for representative animals after including samples from additional locales in Belize, Guatemala and Mexico. While there is limited evidence of subdivision involving other locales, we found that most of the differentiation among populations of C. moreletiican be attributed to animals collected from a single locale in Belize, Banana Bank Lagoon. Furthermore, mitochondrial DNA sequence analysis showed that animals from this and certain other locales display a haplotype characteristic of the American crocodile, C. acutus, rather than C. moreletii. We interpret this as evidence of hybridization between the two species and comment on how these new data have influenced our interpretation of previous findings. We also find very low levels of nucleotide diversity in C. moreletiihaplotypes and provide evidence for a low rate of substitution in the crocodilian mitochondrial control region. Finally, the conservation implications of these findings are discussed.

Population status and conservation of Morelet's crocodile, Crocodylus moreletii, in northern Belize

Spotlight surveys were conducted from 1992 to 1997 to determine the population status of Morelets crocodile, Crocodylus moreletii, in northern Belize. A total of 754 crocodiles were observed and 481.9 km surveyed (1.55/km). Encounter rates were highest in non-alluvial (8.20/km) and alluvial (6.11/km) lagoons, and considerably lower in most rivers and creeks (0.95/km), and coastal mangrove habitats (0.24/km). The population sex ratio was significantly male biased (1 female:5.3 males), although the reasons for this are unclear. Comparisons with survey data from 1979 to 1980 suggest substantial population recovery has occurred following legal protection in 1981. At present there are no immediate threats to the continued survival of Morelets crocodile in Belize. Conservation actions should address the creation of additional protected areas in anticipation of future regional development.

Status and conservation of the American crocodile, Crocodylus acutus, in Belize

The status of the American crocodile (Crocodylus acutus) in the coastal zone of Belize was investigated from July 1996 to October 1997. Two hundred and sixty-two crocodiles were observed during spotlight surveys of 952.2 km of the survey route (0.28 crocodiles/km). Encounter rates were highest in the TurneAe Atoll, and low to moderate elsewhere. Most nesting occurs on elevated beach ridges in the TurneAe Atoll. Freshwater and brackish lagoons adjacent to nesting sites provide essential nursery habitat. Despite legal protection, populations are threatened by opportunistic killing, accidental drowning in fishing nets, and habitat destruction, especially the development of critical nesting habitat. Protection of nesting and nursery habitat is of paramount importance for the continued survival of the American crocodile in Belize. # 2000 Elsevier Science Ltd. All rights reserved.

Nesting Ecology of the American Crocodile in the Coastal Zone of Belize

Abstract We conducted a study of American Crocodile nesting ecology in coastal Belize from June 1996 to July 1997. Most nesting areas were found on elevated beach ridges composed of coarse sand. Shallow, brackish lagoons adjacent to nesting areas provide critical nursery habitat for hatchlings. The most significant nesting areas were found in the Turneffe Atoll. American crocodiles construct both hole and mound nests in Belize. Clutches are deposited during the last half of the dry season, from late March to early May. Mean clutch size is 22.3 ± 6.0 eggs. Hatching occurred from late June to mid-July, a period coinciding with the beginning of the wet season. Nesting success was high, and losses to predation and flooding were negligible. Females may defend nests from predators and excavate neonates at hatching, but otherwise parental care appears minimal. The protection of suitable nesting and nursery habitat is essential for the continued survival of the American crocodile in Belize.

Size estimation, morphometrics, sex ratio, sexual size dimorphism, and biomass of Morelet's crocodile in northern Belize

Abstract. We used morphometric data from 1276 Crocodylus moreletii captured in northern Belize (1992–2001) to develop predictive models for determining body size (total length [TL], snout-vent length [SVL]) from measurements of single attributes (dorsal cranial length [DCL], cranial width [CW], snout length [SL] and width [SW], body mass [BM], rear-foot length [RFL]), quantify sexual size dimorphism, examine ontogenetic changes in cranial morphology, re-evaluate maximum body size attained by this species, and estimate standing crop biomass of crocodiles at our principal study site. Strong positive allometric relationships were found between measures of body length and other morphometric attributes, and provide a reliable means to estimate body length from tracks, skulls, and body parts. The maximum DCL:CW ratio is attained at a relatively small body size and preceded a dietary shift from insects and arachnids to vertebrates and ampullarid snails. The SL:SW ratio of C. moreletii is highly variable and because of overlap with C. acutus, deemed of little value for distinguishing these two sympatric species. Both overall and adult sex ratio (female:male) was male biased and differed significantly from parity. The mean SVL of adult males (98.3 ± 21.3 cm) was significantly greater than that of adult females (87.3 ± 15.9 cm). A compressed sexual size dimorphism index (SDI) of 2.12 was calculated for C. moreletii in northern Belize. Based on skull measurements, the current size record for C. moreletii in Belize is 362 cm TL. Standing crop biomass of C. moreletii at our principal study site (Gold Button Lagoon) was estimated to be 9.5 kg/ha.

Biodiversity Conservation in a Changing Climate: A Review of Threats and Implications for Conservation Planning in Myanmar

High levels of species richness and endemism make Myanmar a regional priority for conservation. However, decades of economic and political sanctions have resulted in low conservation investment to effectively tackle threats to biodiversity. Recent sweeping political reforms have placed Myanmar on the fast track to economic development—the expectation is increased economic investments focused on the exploitation of the country’s rich, and relatively intact, natural resources. Within a context of weak regulatory capacity and inadequate environmental safeguards, rapid economic development is likely to have far-reaching negative implications for already threatened biodiversity and natural-resource-dependent human communities. Climate change will further exacerbate prevailing threats given Myanmar’s high exposure and vulnerability. The aim of this review is to examine the implications of increased economic growth and a changing climate within the larger context of biodiversity conservation in Myanmar. We summarize conservation challenges, assess direct climatological impacts on biodiversity and conclude with recommendations for long-term adaptation approaches for biodiversity conservation.

ORGANOCHLORINE PESTICIDES IN CHORIOALLANTOIC MEMBRANES OF MORELET'S CROCODILE EGGS FROM BELIZE

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 Morelets 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.

Evidence of multiple paternity in Morelet's Crocodile (Crocodylus moreletii) in Belize, CA, inferred from microsatellite markers

Microsatellite data were generated from hatchlings collected from ten nests of Morelets 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.

OCULAR DISEASE IN AMERICAN CROCODILES (CROCODYLUS ACUTUS) IN COSTA RICA

Beginning in early 2006, an ocular disease of unknown etiology was routinely observed in American crocodiles (Crocodylus acutus) inhabiting the highly polluted Tarcoles River in west-central Costa Rica. We examined the nature and incidence of ocular disease in Tarcoles crocodiles and assessed the possible association between the disease and accumulation of chemical pollutants in diseased individuals. During 12–15 September and 12–13 December 2007, crocodiles were captured and examined for ocular disease and sampled to determine environmental contaminant accumulation. Three of 11 (27.3%) crocodiles captured (all males) exhibited unilateral ocular disease, primarily characterized by corneal opacity and scarring, anterior synechia, and phthisis bulbi. Multiple pollutants were detected in crocodile caudal scutes (organochlorine pesticides [OCPs] and metals), crocodile blood (OCPs), and sediments (OCPs and metals) from the Tarcoles, but no associations were found between contaminant accumulation and the incidence of eye disease. On the basis of the limited number of diseased animals examined and the potential exposure of crocodiles to pathogens and other pollutants not targeted in this study, we cannot rule out infection or chemical toxicosis as causes of the eye lesions. However, circumstantial evidence suggests that the observed ocular disease is likely the result of injury-induced trauma (and possibly secondary infection) inflicted during aggressive encounters (e.g., territorial combat) among large adult crocodiles living at relatively high densities.