The American crocodile (Crocodylus acutus) is a widely distributed species across coastal and brackish areas of the Neotropical region of the Americas and the Greater Antilles. Available information on patterns of genetic differentiation in C. acutus shows a complex structuring influenced by interspecific interactions (mainly hybridization) and anthropogenic actions (mostly historical hunting, recent poaching, habitat loss and fragmentation, and unintentional translocation of individuals). In this study, we used data on mitochondrial DNA control region and 11 nuclear polymorphic microsatellite loci to assess the degree of population structure of C. acutus in South America, North America, Central America and the Greater Antilles. We used traditional genetic differentiation indices, Bayesian clustering and multivariate methods to create a more comprehensive picture of the genetic relationships within the species across its range. Analyses of mtDNA and microsatellite loci show evidence of a strong population genetic structure in the American crocodile, with unique populations in each sampling locality. Our results support previous findings showing large degrees of genetic differentiation between the continental and the Greater Antillean C. acutus. We report three new haplotypes unique to Venezuela, which are considerably less distant from the Central and North American haplotypes than to the Greater Antillean ones. Our findings reveal genetic population differentiation between Cuban and Jamaican C. acutus and offer the first evidence of strong genetic differentiation among the populations of Greater Antillean C. acutus.

Hunting caimans (Caiman spp.) with baited hooks in the Brazilian Amazon represents one of the largest illegal wildlife industries in the world. Our objective was to evaluate the effects of water level, distance from settlements, and hunting effort on caiman meat production. In 2008, we accompanied 31 caiman hunting expeditions in and around a wetland protected area located in the Amazon-Purus interfluve in Brazil. We measured and weighed all captured caimans. We used simple and multiple linear regressions to analyze our data. The hunting technique is not selective for the capture of spectacled caimans (Caiman crocodilus) or black caimans (Melanosuchus niger) and occurs throughout the year. Fresh-meat production was similarly correlated with individuals weights for both species. Hunting success was strongly related to river level, distance from human settlements, and hunting effort. We estimated an annual production of 37,050 kg of meat from the study area, representing 3,562 caimans harvested and gross earnings of $18,500 (U.S.). Caiman hunting was the principal source of income for hunters and their families but resulted in low returns, and large black caiman were not taken, indicating possible overhunting. (C) 2016 The Wildlife Society.

The genus Crocodylus comprises 12 currently recognized species, many of which can be difficult to differentiate phenotypically. Interspecific hybridization among crocodiles is known to occur in captivity and has been documented between some species in the wild. The identification of hybrid individuals is of importance for management and monitoring of crocodilians, many of which are Convention on International Trade in Endangered Species (CITES) listed. In this study, both mitochondrial and nuclear DNA markers were evaluated for their use in confirming a suspected hybrid zone between American crocodile (Crocodylus acutus) and Morelet’s crocodile (Crocodylus moreletii) populations in southern Belize where individuals and nests exhibiting atypical phenotypic features had previously been observed. Patterns observed in both phenotypic and molecular data indicate possible behavioural and ecological characteristics associated with hybridization events. The results of the combined analyses found that the majority of suspected hybrid samples represent crosses between female C. acutus and male C. moreletii. Phenotypic data could statistically identify hybrids, although morphological overlap between hybrids and C. moreletii reduced reliability of identification based solely on field characters. Ecologically, C. acutus was exclusively found in saline waters, whereas hybrids and C. moreletii were largely absent in these conditions. A hypothesized correlation between unidirectional hybridization and destruction of C. acutus breeding habitats warrants additional research.

Rates of growth and survival in wild populations are affected by the physical environment, biotic interactions, and density-dependent processes, such as growth and fecundity. However, the relative importance of these factors in long-lived reptiles is poorly understood. We analyzed growth rates of Melanosuchus niger and Caiman crocodilus coexisting in two areas of the Brazilian Amazon with very different environmental characteristics. Growth rates of Caiman crocodilus at the two sites were similar, but M. niger grew more slowly in the area with higher productivity and higher density of caimans. Growth rates of the same species from other sites and of the temperate-zone Alligator mississippiensis indicate large differences among sites, but little evidence that these differences are primarily due to differences in productivity or temperature. Demographic models used to estimate sustained yields from caiman harvests should take into account the likely importance of density-dependent growth.

The Siamese Crocodile (Crocodylus siamensis) is critically endangered and, until a decade ago, few remaining wild populations were known to exist. Described here are the first in-depth surveys for C. siamensis in Laos with new field data on ecology and conservation. Small breeding populations of C. siamensis are confirmed to persist in Laos. During surveys between 2003 and 2008, C. siamensis was recorded in 13 sites of six river systems, where at least 36 individuals (1-11 per site) were documented. In all sites, crocodile densities and recruitment rates were extremely low. Eight nests were recorded among the first wild nests of C. siamensis to be reported. Perennial, thickly vegetated floodplain lakes are critical dry-season refugia and breeding habitats for C. siamensis in Laos. Opportunistic collection of crocodiles by local communities was observed, and at all sites there is increasing degradation of floodplain lakes for agriculture or economic development. National crocodile records were compiled and indicate that, historically, C. siamensis was widespread in lowland riverine and palustrine habitats of Laos, with most records from Central and South Laos in the Mekong Plain. These records also suggest that a severe range decline has occurred over the past century, although most wetlands remain unsurveyed for crocodiles. Crocodylus siamensis is probably now extirpated from the Lao Mekong and many other wetlands. Remnant C. siamensis populations in Laos are of global importance. All documented breeding sites, and most confirmed national records, are in rural lands outside the national protected area system, and conservation efforts will require community-based approaches.

We studied diet and size-related dietary patterns among American Crocodiles (Crocodylus acutus) in marine habitats of coastal Belize (1996-1997). Prey items recovered from crocodile (N = 97) stomach contents included insects, mollusks, crustaceans, fish, amphibians, reptiles, birds, and mammals. Based on an overlapping group analysis of percent occurrence, we concluded that hatchlings and small juveniles feed largely on insects and crustaceans, larger juveniles broaden their diet to include fish and nonfish vertebrates, subadults consume increasing amounts of crustaceans with lesser amounts of insects and nonfish vertebrates, and adults subsist primarily on marine crustaceans. Dietary diversity was uniformly low across all size classes but greatest among small and large juveniles. Conversely, hatchlings, subadults, and adults had the most specialized (least diverse) diet owing to reliance upon a limited selection of prey, largely insects (hatchlings) or crustaceans (subadults and adults). Dietary overlap was greatest between adjacent size classes and lowest between the largest and smallest size classes. The high prevalence of freshly ingested prey among all size classes indicates frequent, regular feeding by C. acutus in coastal habitats, perhaps driven by the relatively small size of frequently consumed prey such as crabs. Because crabs have a blood salt content equivalent to the external medium and comprise a large portion of the diet, these prey likely impose a high osmoregulatory burden on C. acutus inhabiting hyperosmotic coastal environments. Contrary to earlier assertions that salt glands in C. acutus lack the excretory capacity to balance salt and water, we suggest populations in coastal Belize rely on these glands in addition to behavioral strategies to maintain osmotic homeostasis.

The Siamese Crocodile (Crocodylus siamensis) is one of the most endangered crocodilians in the world, and wild populations throughout Southeast Asia have precipitously declined over the last 50 years. Although initially feared extinct in Thailand, surveys in 2001 located a remnant population of C. siamensis in Kaeng Krachan National Park (KKNP), an extensive (2,915 km(2)) protected area along the Thai-Myanmar border. Our objectives were to assess the conservation status of C. siamensis populations within the park, determine if reproduction is occurring, and develop conservation recommendations based on these findings. We used a combination of nocturnal spotlight counts, track and sign surveys, and village interviews to census crocodile populations in KKNP from 2009-2011. Interview data suggest crocodiles occasionally enter Kaeng Krachan Reservoir, although we observed none during spotlight counts. No evidence of crocodiles was found on the Mae Pradone River. We recorded 10 detections of crocodile sign (tracks and scat) along the Petchburi River, although overall detection rates were low (<0.30/km). We found three nests along the Petchburi River from 2009-2011. Differences in mean egg width among clutches suggest one to three females nested. Clutches were considerably larger than those reported from other wild populations, but contained only non-viable eggs, possibly due to an insufficient number (or complete absence) of males in the Petchburi River. Collectively our survey data suggest at least four, and perhaps as many as six non-hatchling C. siamensis inhabit KKNP. The viability of this small population is doubtful and without direct conservation action, extinction appears inevitable. To avoid this fate, the existing population should be augmented using crocodiles obtained from commercial farms in Thailand.

SummaryIndia'sChambalRiver hosts the largest population of the critically endangered gharial. Boat‐based daylight surveys to date only provide indices of relative abundance, without measures of survey bias or error. No attempt to quantify detection probabilities in these surveys has yet been made, and thus, absolute density estimates of this population remain unknown.We surveyed 75 km of theRiverChambal and photographed individual gharials for capture–recapture analysis. The total sampling effort yielded 400 captures. Population closure was supported (z = −1·48,P = 0·069), and closed‐population models were used to estimate abundances.Models were selected using theAkaikeInformationCriterion (AIC) index of model fit. The best model estimated 231 ± 32 adult, 83 ± 23 subadult and 89 ± 19 juvenile gharials (Mean ± SE), respectively, while the model‐averaged estimate was 220 ± 28 adult, 76 ± 16 subadults and 93 ± 16 juvenile gharials, respectively.The best model estimated absolute densities of 3·08 ± 0·43, 1·11 ± 0·3 and 1·19 ± 0·25 adult, subadult and juvenile gharials km−1, respectively, while the model‐averaged estimate was 2·93 ± 0·37, 1·01 ± 0·21 and 1·24 ± 0·21 adult, subadult and juvenile gharials km−1, respectively, compared with relative densities of 0·94, 0·45 and 0·30 adult, subadult and juvenile gharials km−1, respectively, from boat‐based daylight surveys. On the basis of our best model, we suggest a detection probability based correction factor of 3·27, 2·47 and 3·97 to boat‐based daylight survey estimates of adult, subadult and juvenile gharials, respectively.Synthesis and applications. Used within the framework of capture–recapture analysis, photoidentification provides a reliable and noninvasive method of estimating population size and structure in crocodilians. We also opine that without determining the current status of gharials, highly intensive strategies, such as the egg‐collection and rear‐and‐release programmes being implemented currently, initiated on the basis of underestimates of population sizes, are unwarranted and divert valuable conservation resources away from field‐based protection measures, which are essential in the face of threats like hydrologic diversions, sand mining, fishing and bankside cultivation.

The Nile crocodile (Crocodylus niloticus) is an ancient icon of both cultural and scientific interest. The species is emblematic of the great civilizations of the Nile River valley and serves as a model for international wildlife conservation. Despite its familiarity, a centuries-long dispute over the taxonomic status of the Nile crocodile remains unresolved. This dispute not only confounds our understanding of the origins and biogeography of the 'true crocodiles' of the crown genus Crocodylus, but also complicates conservation and management of this commercially valuable species. We have taken a total evidence approach involving phylogenetic analysis of mitochondrial and nuclear markers, as well as karyotype analysis of chromosome number and structure, to assess the monophyletic status of the Nile crocodile. Samples were collected from throughout Africa, covering all major bioregions. We also utilized specimens from museum collections, including mummified crocodiles from the ancient Egyptian temples at Thebes and the Grottes de Samoun, to reconstruct the genetic profiles of extirpated populations. Our analyses reveal a cryptic evolutionary lineage within the Nile crocodile that elucidates the biogeographic history of the genus and clarifies long-standing arguments over the species' taxonomic identity and conservation status. An examination of crocodile mummy haplotypes indicates that the cryptic lineage corresponds to an earlier description of C. suchus and suggests that both African Crocodylus lineages historically inhabited the Nile River. Recent survey efforts indicate that C. suchus is declining or extirpated throughout much of its distribution. Without proper recognition of this cryptic species, current sustainable use-based management policies for the Nile crocodile may do more harm than good.

The conservation of species is one of the foundations of conservation biology. Successful species conservation has often been defined as simply the avoidance of extinction. We argue that this focus, although important, amounts to practicing conservation at the “emergency room door,” and will never be a sufficient approach to conserving species. Instead, we elaborate a positive definition of species conservation on the basis of six attributes and propose a categorization of different states of species conservation using the extent of human management and the degree to which each of the attributes is conserved. These states can be used to develop a taxonomy of species “recovery” that acknowledges there are multiple stable points defined by ecological and social factors. “With this approach, we hope to contribute to a new, optimistic conservation biology that is not based on underambitious goals and that seeks to create the conditions under which Earth's biological systems can thrive.

The Chinese alligator (Alligator sinensis) is considered the most critically endangered crocodilian as a result of the near total loss of its habitat and its extremely small and fragmented wild populations. Plans for population recovery lie mostly with wetland restoration and the reintroduction of captive-reared animals. We carried out a first-trial release of 3 adult Chinese alligators (1♂, 2♀) into a pond at the Hongxing conservation site, Xuancheng, southern Anhui Province; the animals were radio-tracked from May to October in 2003. We hypothesized that after a period of adaptation, the alligators would establish definable home ranges. Two (1♂, 1♀) of the 3 alligators were monitored for the whole of the tracking period. The male had an annual home-range size of 7.61 hm2, and the female 4.00 hm2. Water temperature and pond water level were two important factors influencing the alligators' distributions, and daily movements. The radio-tracked alligators had overlapping home ranges, which notably included the one substantial island in the pond; that island is the only known nesting site of the local native wild alligators. Aggressive interactions between the released alligators and native wild alligators were observed during the breeding season around this island. All the three reintroduced alligators survived the winter of 2003 and were alive in the same pond in 2008. We concluded that the Hongxing conservation site provided a suitable habitat for the reintroduced alligators. However, the low water level in the pond resulting from farmland irrigation in August and September can be a substantial threat to the alligators' survival. Therefore, regulations on irrigation in summer and autumn are needed to balance the water needs of the alligators and agriculture.

Among crocodilians, Crocodylus rhombifer is one of the world's most endangered species with the smallest natural distribution. In Cuba, this endemic species coexists with the American crocodile (Crocodylus acutus). Hybridization between these two species is well known in captivity and might occur in the wild, but has never been demonstrated genetically. Here, we combined molecular data with environmental, geographic, and fossil data to infer the evolutionary history of Crocodylus in the Cuban Archipelago, and to evaluate genealogical support for species boundaries. We analyzed seven microsatellite loci plus DNA sequence data from nuclear (RAG-1) and mitochondrial (cytochrome b and cytochrome oxidase I) genes from 89 wild-caught individuals in Cuba, Grand Cayman Island, Jamaica, and Central America, and two samples from zoo collections. Microsatellites showed evidence of introgression, suggesting potential hybridization among Cuban groups. In Cuba, C. acutus contained one mitochondrial DNA (mtDNA) haplotype, whereas C. rhombifer contained two haplotypes. MtDNA data showed that C. acutus is paraphyletic with respect to C. rhombifer, revealing 1% sequence divergence between species within Cuba vs. 8% divergence between Cuban forms and mainland C. acutus. We suggest that hybridization has been a historical as well as a current phenomenon between C. acutus and C. rhombifer. These findings suggest that long-term conservation of crocodiles in Cuba will require identification of genetically pure and hybrid individuals, and a decrease in anthropogenic activities. We also recommend more extensive morphological and genetic analyses of Cuban population to establish clear boundaries of the hybrid zone between C. acutus and C. rhombifer.

We used morphometric data from 151 Crocodylus acutus captured in the Coastal Zone of Belize to develop predic - tive models for deducing body size (total length (TL) and 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), and rear foot length (RFL)), quantify sexual size dimorphism, examine ontogenetic changes in cranial morphology, and estimate standing crop biomass of crocodiles on an offshore atoll. Strong positive allometric relationships were found between measurements 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 of 2.4 was attained at a body size that coincided with a dietary shift from in - vertebrates to larger vertebrate prey. The SL:SW ratio of C. acutus partially overlapped that of C. moreletii, and consequently this attribute was not useful for distinguishing these two morphologically similar, sympatric species. The mean DCL:TL ratio was 0.15 and remained constant across body sizes ranging from hatchlings to large adults. Both overall and adult sex ratio (female:male) were not significantly different from parity. The mean SVL of males (111.3 ± 20.7 cm) was significantly greater than that of females (101.0 ± 6.2 cm). A compressed sexual size dimorphism index (SDI) of 2.10 was calculated for C. acutus in coastal Belize. Crocodylus acutus in coastal Belize appear to attain a smaller body size than reported for other populations. Standing crop biomass of C. acutus in the Turneffe Atoll was estimated to be 0.92 kg/ha.

Management of crocodilians is often based on source-sink dynamics, protecting breeding habitat and concentrating hunting in other areas. Nest distributions shed light on habitat use by breeding populations, which might be used as a basis for monitoring and management. The heterogeneous spatial distribution of Melanosuchus niger and Caiman crocodilus in Amazonia has been suggested to reflect past hunting pressure, often underestimating the natural ecological peculiarities of these species. Ground nest surveys combined with satellite imagery allowed us to evaluate whether nest-site use by M. niger and C. crocodilus reflects environmental constraints or is a result of hunting pressure. Our results indicate that there is little evidence that hunting pressure shapes nest-site use of these species in our study areas. M. niger nests mainly on the shores of stable, temporally impounded floodplain lakes isolated from the early stages of the annual rising water of main rivers. This behavior facilitates the identification of suitable nesting sites using moderate-resolution remote-sensing tools and should guide monitoring efforts and the protection of these areas. In contrast, C. crocodilus is a generalist species, able to nest hundreds of meters inside the forest far from permanent water. This makes the occurrence and distribution of nesting-sites unpredictable using Landsat images. Although nests of this species can be found around lakes where nests of M. niger also occur, the protection of these sites might help to preserve only a small portion of C. crocodilus nesting females. Thus, conservation strategies for C. crocodilus should probably be based on different approaches.

The jaguar (Panthera onca) is the largest Neotropical felid and in many parts of its range reptiles form a significant but relatively minor component of its diet. However, in the seasonally flooded varzea forests of the Amazon, terrestrial mammals, which form an important component of jaguar diet in other habitats, are largely absent and jaguars switch to alternative prey, including arboreal mammals and reptiles. In the Mamiraua Sustainable Development Reserve in the western Brazilian Amazon, we document predation by jaguars on two species of caiman (Caiman crocodiles and Melanosuchus niger), which are abundant in this varzea habitat. The smaller C. crocodiles seems to be particularly vulnerable because of its size and tendency to spend more time on land than the larger M. niger. Jaguars not only kill and eat caiman but are also a significant predator on eggs of both species. We place our findings into the context of jaguar predation on reptiles by reviewing studies of jaguar diet in a variety of biomes.

The habitat of C. acutus consists largely of brackish water coastal habitats such as the saltwater sections of rivers, coastal lagoons, and mangrove swamps. However, populations are known from freshwater areas located well inland, including a number of reservoirs. A signifi cant population is known from Lago Enriquillo, a landlocked hypersaline lake situated 40 m below sea level in the arid southwestern Dominican Republic.

Crocodylus acutus, a coastal species nesting in sand beaches, could be affected by increasing tropical cyclone frequency. We studied key characteristics of C. acutus reproductive ecology on Banco Chinchorro atoll from 2006 to 2009, including the impact of two tropical cyclones. Hurricanes increased canopy openness causing earlier nesting the following year. Crocodiles nested at the beginning of the wet season with hatching in mid-wet season; this could represent a compromise between risking nest flooding and increasing freshwater availability for hatchlings. Tropical cyclones dramatically reduced nesting success by cooling and flooding clutches. Nursery sites were usually hypersaline, but heavy rainfall from tropical cyclones can likely benefit hatchling survival by decreasing salinity. While tropical cyclones have negative short-term impacts on crocodile nesting, they likely have an overall beneficial effect by creating and maintaining open sandy nesting areas used by C. acutus and they may explain its widespread distribution in Caribbean coastal areas.

We here describe scalation in a large sample (n = 80) of American crocodiles, Crocodylus acutus, collected from the coastal zone of northern Belize. Differences between our data and the few published descriptions of C. acutus were found among post-occipital, nuchal, dorsal, ventral, and double-crested caudal scale groups, suggesting that interpopulational differences in scalation may exist in this widely distributed species. Whether populations can be identified on the basis of scalation remains to be determined.

Snakes: Ecology and Conservation . S. J. Mullin, and R. A. Seigel , editors. 2009. Comstock Publishing Associates, Ithaca, NY. ( xiv+365) pp. $60.00 (hardcover). ISBN 978-0-8014-4565-1. Snakes are a particularly intriguing group of animals, not only because they have unique morphologies and many distinctive life histories and behaviors but also because they are simultaneously fascinating and dreadful. Snakes are a widespread and ecologically successful group and are one of the most prominent animals in the constellation of human mythologies. The snake is ingrained in our psyche, yet until relatively recently we knew relatively little about snakes. There was even a feeling among some herpetologists in the 1990s (only partially facetious) that snake biologists had “lizard envy” because this sister group of squamates was generally easier to study and was being proclaimed by some as the model organisms for herpetological research. Although snakes are nearly ubiquitous cultural icons, like many other taxonomic groups they are affected by the degradation of our biosphere, and there is a growing need to devote effort to the conservation of snakes and other animals that Linnaeus once famously referred to as “foul and loathsome” but which hold a special place in the ecosystems of our world and in the hearts of many biologists. Many of the world's leading experts on snakes contributed to Snakes: Ecology and Conservation, and the book is an admirable review of the biology of snakes and serves as a foundation for their conservation and management. Mullin and Seigel build on two previous volumes on the ecology, evolution, behavior, and conservation of snakes, which Seigel and others coedited. The first two books were authoritative and wide-ranging treatments of snake biology, and each had a single chapter on snake conservation, both by Ken Dodd. Dodd (1987) reviewed what was known globally about the conservation status of snakes and made a brief foray into the topic of biological considerations for snake conservation. In 1993 Dodd built on this latter theme and provided a more detailed review of the conservation biology of snakes. Now, after more than 15 years, Mullin and Seigel and contributors have expanded the treatment of snake conservation with considerable new and updated information. Everyone who works with or has a strong interest in snakes should buy this book. Undoubtedly the volume will be a standard reference for some time to come and will play an important role in building the tool kits of those interested in the conservation of snakes. Chapter topics are broad and include innovative techniques for the study of snakes, molecular phylogeny and conservation genetics, the application of studies of snake behavior and reproduction to conservation and management, the use of intensive management (captive breeding and repatriation), and management of snake habitat and modeling of landscape approaches. Snake conservationists usually start out at a disadvantage because of the widespread animosity toward snakes among the general public. The chapter by Burghardt et al. discusses the basis of such ophiophobia and mitigation of its effects. As a herpetologist who does not work much with snakes, I found the book enjoyable and informative because it brought me up to date with the large body of research that has been conducted on snakes over the last two decades. Most of the chapters address topics of both general and specific interest in which snakes are the subject of case studies, so the book does have a wider appeal to students of conservation biology. That is its strength. Its main limitation in my view is that the reader is not presented a broader perspective of snake conservation in the sense of how snakes are faring worldwide or what efforts are underway to conserve highly endangered groups of snakes. Throughout the book, the motivation for conservation of snakes is an underlying assumption that is not made explicit. I think a review chapter on the status of snakes and threats they face worldwide would have been a welcome addition. One of the reasons for beginning this series of books in the 1980s was the scattered state of information on snake biology. A similar situation exists today with snake conservation. There is no one source that not only delves into the depths of the ecology, behavior, and genetics of snakes and how these factors influence management and conservation efforts (which this book admirably does), but also examines the main threats to snakes and how to reduce them. What are the challenges for people working for the conservation of critically endangered groups, such as the vipers in the Caucasus region of Asia or some of the island snakes endemic to the Caribbean or Philippines? My comments do not detract from the quality of the chapters in this book, but perhaps instead speak to my desire for a future volume that reviews and synthesizes these other important aspects of snake conservation. Nevertheless, Snakes: Ecology and Conservation provides an excellent and up-to-date account of the research on snakes and provides a broad biological foundation for the conservation of this unique group of animals. Editor's Note: John Thorbjarnarson, a world-class herpetologist and conservationist valued by people from China to Brazil and a treasured colleague at the Wildlife Conservation Society, died suddenly in February. He will be sorely missed by many.