Search

Simple Summary: Crocodiles are one of nature's most successful predators. Their prey varies according to their size. Adults are known to consume different types of vertebrates; juveniles have a similar diet, although their prey is smaller. However, hatchlings have a diet based mainly on insects. This study aimed to know the diet of hatchling Morelet's crocodiles (Crocodylus moreletii) at a growth stage corresponding to their transition to the juvenile stage. Therefore, it is important to know which vertebrate prey are beginning to appear during this developmental change in crocodiles. To find out, we captured and washed the stomachs of 31 hatchling crocodiles in the Laguna de las Ilusiones in Tabasco, Mexico. Our results showed that crocodiles have a generalist diet, with prey ranging from invertebrates (mainly coleoptera and hemipterans) to some vertebrates (mostly fish and birds). It is important to know these changes in the diet of crocodilians as they develop to help us better interpret their natural history and propose better strategies for their study. The relationship between diet and behavior is essential to understanding an animal's strategies to obtain food, considering ontogenical changes. In reptiles, there is a relationship between the length of the individual and the size of the prey it consumes. Studies have focused on the ontogenetic changes in reptile diets from hatchling to adult, but only a few studies have focused on the transition from hatchling to juvenile. We aimed to describe and analyze the composition, variation, diversity, and overlap in the diet of hatchling Morelet's crocodiles (Crocodylus moreletii) for three size intervals during the hatchling–juvenile transition. We captured 31 hatchling Morelet's crocodiles in an urbanized lagoon in Tabasco. We performed stomach-flushing to determine the diet. Additionally, we estimated the volume, frequency of occurrence, and relative importance of diet items and analyzed the relationship between prey type and the total length of the individuals. The diversity of the hatchling prey suggests a generalist diet. We observed two items not previously described in the diet of hatchling crocodiles. In addition, we found differences in diet between the initial and final size intervals, as increases in the length of prey appeared that they did not consume when they were hatchlings. Our results contribute new information to the dietary changes that occur during the hatchling–juvenile transition. [ABSTRACT FROM AUTHOR]

In an age of emerging zoonoses, it is important to understand the intricate system of vectors and reservoirs, or hosts, and their relation to humans. West Nile Virus (WNV) has been detected in a myriad of nonhuman hosts. Transmission of the virus to humans is reliant on amplified seroprevalence within the host, which occurs primarily in birds. However, recent studies have found that other animal groups, including crocodilians, can obtain seroprevalence amplification to levels that make them competent hosts able to transmit WNV to mosquitoes, which can then transmit to humans. Climate change could exacerbate this transmission risk by shifting the distributions of mosquito vectors towards novel geographic ranges. Here, we use maximum entropy models to map the current and future distributions of three mosquito vector species and four crocodilian species in North America to determine the emerging risk of WNV outbreaks associated with changing climates and WNV associated with crocodilians in North America. From our models, we determined that one mosquito species in particular, Culex quinquefasciatus, will increase its distribution across the ranges of all crocodilian species in all tested climate change scenarios. This poses a potential risk to public health for people visiting and living near crocodilian farms and high-density natural crocodilian populations. [ABSTRACT FROM AUTHOR]

The principal effect controlling the oxygen affinity of vertebrate haemoglobins (Hbs) is the allosteric switch between R and T forms with relatively high and low oxygen affinity respectively. Uniquely among jawed vertebrates, crocodilians possess Hb that shows a profound drop in oxygen affinity in the presence of bicarbonate ions. This allows them to stay underwater for extended periods by consuming almost all the oxygen present in the blood-stream, as metabolism releases carbon dioxide, whose conversion to bicarbonate and hydrogen ions is catalysed by carbonic anhydrase. Despite the apparent universal utility of bicarbonate as an allosteric regulator of Hb, this property evolved only in crocodilians. We report here the molecular structures of both human and a crocodilian Hb in the deoxy and liganded states, solved by cryo-electron microscopy. We reveal the precise interactions between two bicarbonate ions and the crocodilian protein at symmetry-related sites found only in the T state. No other known effector of vertebrate Hbs binds anywhere near these sites. Crocodilians are ambush predators that possess haemoglobin with an allosteric switch between R (high oxygen affinity) and T (low oxygen affinity) forms strongly controlled by bicarbonate ions, a unique evolutionary feature that helps the animal to stay underwater for extended periods of time. [ABSTRACT FROM AUTHOR]

Reptiles and amphibians are largely present in many environments, including domestic areas when they are kept as pet animals. They often harbor zoonotic pathogens, which can pose a serious risk of infection for humans, mainly immunocompromised individuals, the elderly, children, and pregnant women. Several studies have been carried out to verify the role of cold-blooded animals in the epidemiology of some bacteria, mainly Salmonella, whereas scarce attention has been focused on these animals as a source of staphylococci. These bacteria are often antimicrobial-resistant and they act as opportunistic pathogens, which can cause relevant infections in humans and animals, both domestic and wild. Asymptomatic reptiles and amphibians often harbor staphylococcal strains, such as Staphylococcus aureus and coagulase-negative Staphylococcus spp.; however, these bacteria have been associated with clinical conditions that usually appear in animals under stress conditions. In all cases, greater attention should also be focused on staphylococci in cold-blooded animals due to their implications in human and veterinary medicine. [ABSTRACT FROM AUTHOR]

Location of sound sources is a fundamental task of the auditory system. Recent studies have shown that land vertebrates employ an array of sound localization strategies. We have therefore compared auditory brainstem circuits by measuring cell numbers in the cochlear nuclei in relation to brain weight among different groups of reptiles to determine if these behavioral differences are reflected in the organization of the brainstem. In extant archosaurs, the birds and crocodilians, the two ears are weakly connected pressure receivers, and sound direction is computed by binaural interactions in brain involving parallel processing of interaural time and level differences. The first-order cochlear nuclei are nucleus magnocellularis (NM) and nucleus angularis (NA). NM projects bilaterally to the nucleus laminaris (NL), where interaural time differences are computed in archosaurs. Relative to brain size, NA, NM and NL cell counts of the American alligator (Alligator mississippiensis) are similar to those of birds. Testudines (turtles and tortoises), sister group to archosaurs, are also assumed to compute sound location from binaural interactions in the brain due to weakly connected middle ears. Compared to archosaurs, NA, NM and NL of the red-eared slider (Trachemys scripta), common snapping turtle (Chelydra serpentina) and Hermann’s tortoise (Testudo hermanni) are all proportionally small. In lizards, due to the strong internal coupling of the middle ears, the cochlear nerve responses are directional, and interaural time and level differences are co-dependent and frequency dependent, suggesting that the neural processing of sound direction may be different from archosaurs. Compared to archosaurs, NM and NL of the tokay gecko (Gekko gecko) and green iguana (Iguana iguana) are proportionally small, but NA is well-developed, suggesting a greater importance of the NA pathway for the processing of the high-frequency directional information generated by the coupled ears. Snakes originated from lizard ancestors, but have secondarily lost their eardrums, and their sound localization strategies are unknown. NA and NM of the western ratsnake (Pantherophis obsoletus) are proportionally smaller than those of the lizards.

Fossil feathers have transformed our understanding of integumentary evolution in vertebrates. The evolution of feathers is associated with novel skin ultrastructures, but the fossil record of these changes is poor and thus the critical transition from scaled to feathered skin is poorly understood. Here we shed light on this issue using preserved skin in the non-avian feathered dinosaur Psittacosaurus. Skin in the non-feathered, scaled torso is three-dimensionally replicated in silica and preserves epidermal layers, corneocytes and melanosomes. The morphology of the preserved stratum corneum is consistent with an original composition rich in corneous beta proteins, rather than (alpha-) keratins as in the feathered skin of birds. The stratum corneum is relatively thin in the ventral torso compared to extant quadrupedal reptiles, reflecting a reduced demand for mechanical protection in an elevated bipedal stance. The distribution of the melanosomes in the fossil skin is consistent with melanin-based colouration in extant crocodilians. Collectively, the fossil evidence supports partitioning of skin development in Psittacosaurus: a reptile-type condition in non-feathered regions and an avian-like condition in feathered regions. Retention of reptile-type skin in non-feathered regions would have ensured essential skin functions during the early, experimental stages of feather evolution. The evolution of feathers is associated with the evolution of related skin microstructures. Here, the authors demonstrate that Psittacosaurus, a non-avian feathered dinosaur, retained scaled skin like its ancestors in body regions lacking feathers. [ABSTRACT FROM AUTHOR]

The gharial Gavialis gangeticus is a Critically Endangered crocodilian currently known from only 14 disjunct locations in Nepal and India. The protected stretch of the Babai River in Bardia National Park, Nepal, is home to one of the six subpopulations of gharials that have exhibited recent evidence of reproduction. However, there is limited information available on the gharial population in this region. We conducted surveys during the breeding, nesting and hatching seasons of gharials during 2020–2022 to study the gharial population in the Babai River in Bardia National Park. We located one breeding group of gharials in Soth Khola (2–3 individuals) and one in Dhanuse (5–6 individuals), and we observed pre-mating or mating behaviours in all 3 years. We identified potential nesting areas on sand banks of 19–175 m in length. During nesting seasons we found abundant signs of nesting only in Dhanuse, including entry and exit trails of female gharials to and from the water and trial nests. In 2020 and 2021 we did not find any signs of hatching, probably because of flooding. In 2022 we recorded two gharial nests, producing c. 60 hatchlings, in Dhanuse. Our findings indicate that the gharial population in the Babai River is probably nesting annually. We recommend various conservation actions for this gharial population. [ABSTRACT FROM AUTHOR]

A case of a non-fatal crocodile attack on a human was reported on the banks of the Segovia River on the Honduras and Nicaragua border. The 12-year-old girl survived the attack, only with damage to the tibia of her right leg, where she lost part of the muscle tissue due to the bite. It was after the attack that the American crocodile was shot and killed by local people. In this paper, we discuss the possible causes of crocodile attacks. [ABSTRACT FROM AUTHOR]

Trait datasets are increasingly being used in studies investigating eco-evolutionary theory and global conservation initiatives. Reptiles are emerging as a key group for studying these questions because their traits are crucial for understanding the ability of animals to cope with environmental changes and their contributions to ecosystem processes. We collected data from earlier databases, and the primary literature to create an up-to-date dataset of reptilian traits, encompassing 40 traits from 12060 species of reptiles (Archelosauria: Crocodylia and Testudines, Rhynchocephalia, and Squamata: Amphisbaenia, Sauria, and Serpentes). The data were gathered from 1288 sources published between 1820 and 2023. The dataset includes morphological, physiological, behavioral, and life history traits, as well as information on the availability of genetic data, IUCN Red List assessments, and population trends. [ABSTRACT FROM AUTHOR]

The Siamese Crocodile Crocodylus siamensis is considered one of the most imperiled and poorly-studied crocodilians in the world. Translocations (reintroductions) - often in conjunction with head-starting of juveniles - are a critical component of efforts to restore viable wild populations of C. siamensis. We here report the first confirmed nesting by a known-age, head-started, and translocated female C. siamensis together with observations of nest attendance and nest-associated fauna based on camera trap imagery. Our observations occurred in the Greater Xe Champhone Wetland Complex (GXCWC) in Savannakhet Province, Lao PDR. GXCWC encompasses 45,000 ha of seasonally inundated natural and anthropogenic wetlands, agricultural ecosystems, scrubland, and forest. While collecting eggs for incubation in May 2022, we were able to identify a unique series of notched tail scutes on a female C. siamensis as she aggressively defended a nest. From these markings we determined the female was hatched on 11 August 2012 (age = 9.75 years) and released in March 2014, approximately 3.5 km from the nest site. A game camera placed at the nest on 11 May 2022 and recovered on 5 July 2022 (34 trap nights) recorded 1724 images. These images indicated the female remained in attendance at the nest throughout the monitoring period. Camera trap imagery captured eight nest repair events and two nest defense events; during the latter the female defended the nest from village dogs. Eleven species of nest-associated fauna were recorded by the game camera, including eight and three species of birds and mammals, respectively. Our observations are the first confirmed nesting by a head-started, translocated female C. siamensis indicating these are effective conservation strategies for restoring wild populations. We also unequivocally established that head-started female C. siamensis are capable of reproducing when nine-years-old. [ABSTRACT FROM AUTHOR]

Simple Summary: We aimed to evaluate the efficacy of nuisance crocodile relocations using passive spatial quantification in Guanacaste, Costs Rica. Nuisance relocated crocodiles and wild crocodiles were fit with Iridium satellite trackers and movements of all individuals were monitored over months. Nuisance relocated crocodiles either returned to the area of nuisance, or potentially attempted to return, in short time frames. These results highlight the need for alternative management strategies. Anthropogenic alterations of the environment have increased, highlighting the need for human–wildlife coexistence and conflict mitigation. Spatial ecology, and the use of passive satellite movement technology in particular, has been used to identify patterns in human–wildlife conflict as a function of shared resources that present potential for dangerous situations. Here, we aim to remotely identify patterns indicative of human–crocodile conflict in Guanacaste, Costa Rica by exploring site fidelity and diverse modes of movement (i.e., land and water) across space between nuisance (relocated) and non-nuisance (wild) crocodiles. Advanced satellite remote sensing technology provided near-constant movement data on individuals at the regional scale. Telonics Iridium SeaTrkr-4370-4 transmitters were used with modified crocodilian fitting. Results indicate that relocated crocodiles exhibited large-scale movements relative to wild crocodiles. Nuisance relocated crocodiles either returned to the area of nuisance or potentially attempted to in short time frames. The results presented here highlight the need for alternative management strategies that facilitate relocation efficacy. [ABSTRACT FROM AUTHOR]

This study adopts a new approach describing palaeohydrology and palaeoclimates based on the interpretation of stable oxygen isotopes (δ18 O p) recorded in fossil crocodilian teeth. They represent an archive of prime interest for tracking freshwater palaeoenvironmental change, applicable to many palaeontological localities in the world: crocodilian teeth are abundant in continental basins and have been widely distributed since their diversification during the Mesozoic; the enamel phosphate is resistant to diagenesis and retains its original isotopic composition over geological timescales; and their δ18 O p mainly relies on that of the crocodilian's home waterbody (δ18 O w), which in turn reflects waterbody types, regional climate, and evaporation conditions. This study presents the first application of this theoretical interpretative model to the Shungura Formation (Lower Omo Valley, Ethiopia), a key witness of the important environmental change in eastern Africa during the Plio-Pleistocene that impacted the evolution of regional faunas, including humans. In this complex and variable environmental context, the δ18 O p of coexisting crocodilians allows for the fingerprinting of the diversity of aquatic environments they had access to at a local scale. This study sheds light on two important results: the δ18 O p of crocodilian teeth (1) indicates stable aquatic environments in the northern Turkana Depression from 2.97 to ca. 2.57 Ma but a decline in local waterbodies diversity after 2.32 Ma, suggesting increasing aridity, and (2) shows, like previous geochemical studies on palaeosols and bivalves in the area, a significant increase in δ18 O w from 2.97 to ca. 1.14 Ma, likely due to the shifting air stream convergence zones between the West African and Indian Summer Monsoons and/or reduced rainfall over the Ethiopian Highlands. [ABSTRACT FROM AUTHOR]

The crocodilians include true crocodiles, alligators, caimans, and gharial, and the trade of crocodilian products is regulated in accordance with the Convention of Wild Fauna and Flora (CITES). Hong Kong does not have her own wild crocodilians; thus, all crocodilians meat available is presumably imported with proper license. Here, we obtained a dataset of cytochrome oxidase I (COI) gene markers of 114 crocodilian meat samples (including frozen and dried crocodilian meat products) available in the contemporary market. We have also validated these barcodes in a phylogenetic approach with other data deposited on the GenBank, and detected 112 samples belonging to four crocodile species Crocodylus siamensis, C. porosus, C. niloticus and Alligator mississippiensis, and 2 samples belonging to snake Malayopython reticulatus. The dataset generated in this study will be useful for further studies including meat inspection, illegal trading, and enhancement of international and local legislations on illegal reptile importation. [ABSTRACT FROM AUTHOR]

Reptiles and amphibians are largely present in many environments, including domestic areas when they are kept as pet animals. They often harbor zoonotic pathogens, which can pose a serious risk of infection for humans, mainly immunocompromised individuals, the elderly, children, and pregnant women. Several studies have been carried out to verify the role of cold-blooded animals in the epidemiology of some bacteria, mainly Salmonella, whereas scarce attention has been focused on these animals as a source of staphylococci. These bacteria are often antimicrobial-resistant and they act as opportunistic pathogens, which can cause relevant infections in humans and animals, both domestic and wild. Asymptomatic reptiles and amphibians often harbor staphylococcal strains, such as Staphylococcus aureus and coagulase-negative Staphylococcus spp.; however, these bacteria have been associated with clinical conditions that usually appear in animals under stress conditions. In all cases, greater attention should also be focused on staphylococci in cold-blooded animals due to their implications in human and veterinary medicine.

Simple Summary: The skin of American alligators became lighter when animals were exposed to light colored environments. This change occurred over 2–3 months, and was caused by increased pigmented cells in the dermal layers of the skin. Alligators hatch with bright vertical yellow and black stipes that presumably function as camouflage in emergent vegetation. However, the yellow stripes gradually fade/darken until alligators become a homogenous dark gray/black color as adults. Because alligators live in more temperate climates than other crocodilians, we propose that the loss of yellow stripes might help alligators thermoregulate more efficiently during colder months. We measured the brightness of stripes on wild alligators of a broad spectrum of sizes from three different latitudinal locations within their natural range: northern (South Carolina), central (south Louisiana/southeast Texas), and southern (South Florida). The alligators in South Carolina lost stripes faster as they grew larger, while the alligators in the middle portion of the range became darker at a slower rate, and animals in south Florida lost their stripes at an even slower rate. The loss of stripes at different rates might allow alligators to be more efficient at thermal regulation in the different areas that they inhabit. To assess skin color change in alligators, we maintained animals in differently lighted environments and also measured skin colors in an ontogenetic series of wild animals. Juvenile alligators maintained in black enclosures exhibited a gradual lightening of skin color when shifted to white enclosures, and these observed changes were reversible. A histological examination of the skins of alligators maintained in dark tanks showed that the dermis exhibited a dense layer of pigmented cells, while samples from the same animals in light environments exhibited a more diffuse pigmented layer. As alligators grow, they exhibit an ontogenetic loss of stripes that may aid in crypsis and predation. Hatchlings have intense black and yellow vertical stripes that darken with age; adults are a more homogenous black/gray color. Since alligators live in temperate climates and adults have lower surface area/volume ratios, which can be detrimental for the absorption of radiant energy, the darker color of larger animals may also aid in thermoregulation. Alligators at the northern end of their range, with colder climates, exhibited darker skin tones, and the ontogenetic extinction of stripes occurred at a more accelerated rate compared to animals in southern, warmer regions, supporting the idea that latitude-dependent ontogenetic color shift has a role in thermoregulation. [ABSTRACT FROM AUTHOR]

The evolution of nest site use and nest architecture in the non-avian ancestors of birds remains poorly understood because nest structures do not preserve well as fossils. Nevertheless, the evidence suggests that the earliest dinosaurs probably buried eggs below ground and covered them with soil so that heat from the substrate fuelled embryo development, while some later dinosaurs laid partially exposed clutches where adults incubated them and protected them from predators and parasites. The nests of euornithine birds—the precursors to modern birds—were probably partially open and the neornithine birds—or modern birds—were probably the first to build fully exposed nests. The shift towards smaller, open cup nests has been accompanied by shifts in reproductive traits, with female birds having one functioning ovary in contrast to the two ovaries of crocodilians and many non-avian dinosaurs. The evolutionary trend among extant birds and their ancestors has been toward the evolution of greater cognitive abilities to construct in a wider diversity of sites and providing more care for significantly fewer, increasingly altricial, offspring. The highly derived passerines reflect this pattern with many species building small, architecturally complex nests in open sites and investing significant care into altricial young. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'. [ABSTRACT FROM AUTHOR]

This study adopts a new approach describing paleohydrology and paleoclimates based on the interpretation of stable oxygen isotopes (δ18Op) recorded in fossil crocodilian teeth. They represent an archive of prime interest for tracking freshwater paleoenvironmental change, applicable for many paleontological localities in the world: crocodilian teeth are abundant in continental basins and widely distributed since their diversification during the Mesozoic; the enamel phosphate is resistant to diagenesis and retains its original isotopic composition over geological timescales; their δ18Op mainly relies on that of the crocodilian's home water body (δ18Ow), which in turn reflects water body types, regional climate, and evaporation conditions. This study presents the first application of this interpretative model to the Shungura Formation (Lower Omo Valley, Ethiopia), a key witness of the important environmental changes in eastern Africa during the Plio-Pleistocene that impacted the evolution of regional faunas, including humans. In this complex and variable environmental context, the δ18Op of coexisting crocodilians allows for fingerprinting the diversity of aquatic environments they had access to at a local scale. Like previous geochemical studies performed on paleosols and bivalves in this area, our data indicate a marked increase in δ18Ow between 2.97 Ma and ca. 1.14 Ma, probably resulting from the joint effect of the migration of the air streams convergence zones between the West African and Indian Summer Monsoons and of the decrease in rainfall amounts above the Ethiopian Highlands. Contrary to some conclusions based on terrestrial proxies, the δ18Op of crocodilian teeth does highlight any major change affecting aquatic environments, rather pointing to stability of these environments between 2.97 Ma and ca. 2.57 Ma. By contrast, the diversity of aquatic environments accessible to crocodilians seems to be restricted in most analysed stratigraphical units after ca. 2.32 Ma, a feature that may reflect more arid conditions in the Turkana Depression. [ABSTRACT FROM AUTHOR]

Background: Crocodile farming aims to produce high-quality skins from captive crocodilians. Captivity usually exposes the animals to stressful conditions, resulting in increased serum corticosterone (CORT) levels that correlate negatively with those of sex hormones and reproductive success. Objective: To evaluate serum concentrations of CORT and sex hormones and their relationship in farmed Morelet's crocodiles (Crocodylus moreletii) during the non-breeding (NBS) and breeding (BS) seasons. Methods: The study included 59 adult crocodiles (29 females and 30 males). One blood sample was collected in NBS (n=31) and BS (n=28) from each crocodile to determine serum concentrations of CORT, estradiol (E2), progesterone (P4), and testosterone (T). Crocodiles were kept in mixed-sex groups and were fed once or twice a week throughout the study. Results: In females, CORT was higher in NBS (p<0.05) but had no correlation with E2 or P4 in any season (p>0.05). In males, CORT was similar in NBS and BS (p>0.05) and had no correlation with T (p>0.5). Conclusion: The CORT levels had no effect on sex hormones. This could be explained by low CORT levels resulting from farming conditions where the animals were not exposed to severe or chronic stress. [ABSTRACT FROM AUTHOR]

The independent origins of middle ears in testudinates, lepidosaurs, and archosaurs in the Triassic led to lineage-specific developments in their auditory epithelia. In comparison to the inferred ancestral state, little changed in testudinates, but archosaurs and most lepidosaurs evolved longer, differentiated auditory papillae. In archosaurs, sensory hair cells specialized across and along the papillae, resulting in mainly sensory tall hair cells and mainly mechanically active short hair cells. Crocodilians have 5 mm-long papillae, but relatively low upper frequency limits at around 4 kHz. Avian papillae are mostly 3 to 5 mm in length, being shorter in small species; in owls they exceptionally reach almost 12 mm and have an upper limit of above 10 kHz. Lepidosaurs retained the ancestral papilla as a low-frequency responsive area with one type of hair cell, but most added newly evolved areas (of max. 2 mm length) consisting of oppositely oriented hair cells responding to frequencies above 1 kHz. Initially, these areas flanked both ends of the ancestral area and were redundant in their responses to sound. The evolution of specific configurations in most families eliminated this redundancy, but the paths taken resulted in diverse anatomies that show high degrees of family specificity. Despite these differences, the high-frequency hearing limit of lepidosaurs rarely exceeds 5 kHz. [ABSTRACT FROM AUTHOR]

Herein, we report a small collection of isolated crocodilian teeth recovered from shallow marine Eocene deposits of Turnu Rou (Porceti), Romania. The teeth probably represent an attritional assemblage that could have belonged to several individuals of various sizes and ages, provided with heterodont dentition of at least five morphotypes (slender caniniform, triangular-lanceolate shaped, enlarged conical, slender conical, and low crowned). We assigned the isolated teeth to Gavialoidea based on a number of morphological characters shared with representatives of early gavialoids, known from the early-middle Eocene of western Europe or North Africa. The gavialoids from Turnu Rou represent a new group for the Paleogene of Romania that probably reached the territory of southern Transylvania in the Middle Eocene. Possible scenarios for the origin of southern Transylvanian gavialoids imagine an existence of a western-eastern European route or a migration route direct from North Africa and an ancestor close to the morphology of Maroccosuchus from the region of western Tethys. [ABSTRACT FROM AUTHOR]

Background: Crocodile farming aims to produce high-quality skins from captive crocodilians. Captivity usually exposes the animals to stressful conditions, resulting in increased serum corticosterone (CORT) levels that correlate negatively with those of sex hormones and reproductive success. Objective: To evaluate serum concentrations of CORT and sex hormones and their relationship in farmed Morelet’s crocodiles (Crocodylus moreletii) during the non-breeding (NBS) and breeding (BS) seasons. Methods: The study included 59 adult crocodiles (29 females and 30 males). One blood sample was collected in NBS (n=31) and BS (n=28) from each crocodile to determine serum concentrations of CORT, estradiol (E2), progesterone (P4), and testosterone (T). Crocodiles were kept in mixed-sex groups and were fed once or twice a week throughout the study. Results: In females, CORT was higher in NBS (p0.05). In males, CORT was similar in NBS and BS (p>0.05) and had no correlation with T (p>0.5). Conclusion: The CORT levels had no effect on sex hormones. This could be explained by low CORT levels resulting from farming conditions where the animals were not exposed to severe or chronic stress.

Crocodylians are top predators that play key ecological roles in aquatic ecosystems. As in other groups of large predators, crocodylian populations are often impacted by habitat loss, habitat degradation or direct exploitation for commercial purposes or subsistence. Hence, understanding their spatiotemporal ecology can provide valuable information for conservation planning. We reviewed the published scientific literature on telemetry-tracking in crocodylians, combining the terms "telemetry", "track" or "tag" and variations; "VHF", "UHF", "satellite", "GPS", "radio", "acoustic" or "transmitters"; and "caiman", "alligator", "crocodile", "gharial" or "Crocodylia". Publications retrieved by our search were carefully reviewed for information on study length, geographic location, sample size, taxonomy, and telemetry technology used. We identified 72 research articles in indexed journals and 110 reports available from the IUCN's Crocodile Specialist Group, published between 1970 and 2022. Publications included 23 of the 27-living described crocodylian species. We identified strong geographic and taxonomic biases, with most articles proceeding from the USA (21.2%) and Australia (14%), with Alligator mississipiensis and Crocodylus porosus as the main target species in studies conducted in these countries, respectively. Despite representing 22% of IUCN's reports, Gavialis gangeticus was referred in a single indexed research article. VHF telemetry was the prevalent tracking method, followed by GPS and acoustic transmitters. Studies using VHF devices had generally shorter in length when compared to alternative technologies. Transmitter weight represented less than 2% of the body mass of the carrying individual in all studies. Although attachment site of transmitters was notified in all research papers, few described anaesthetic or clinical procedures during attachment (33%). Our review highlights the need to encourage publication of crocodylian telemetry studies in non-English speaking countries in Asia, Africa, and Latin America, where many endemic species are threatened. We also highlight the need of detailed information on methods and results to facilitate the choice and implementation of appropriate protocols in future telemetry-tracking studies. [ABSTRACT FROM AUTHOR]

Simple Summary: Due to their significant size and aggressiveness, the capture of adult crocodiles carries significant risk, both in terms of stress and injuries to themselves and to operators. Neuromuscular blocking agents act by inducing flaccid muscle paralysis, thereby reducing the physical and chemical risks associated with transportation and anesthesia. Pancuronium bromide and its antagonist, neostigmine methylsulfate, have been successfully used in juvenile and subadult saltwater crocodiles (Crocodylus porosus), but their applications in larger animals (body weight > 230 kg or total length > 3.8 m) or in Nile crocodiles (Crocodylus niloticus) have never been described. We trialed a dose recommendation in nine Nile crocodiles using pancuronium bromide that was originally established for small- and medium-sized saltwater crocodiles, the effect of which can be reversed using neostigmine. We found that the recommended dose caused a prolonged recovery time in adult male Nile crocodiles, and we propose a weight-independent dose for Nile crocodiles with body weight ≥ 300 kg or total length ≥ 4.0 m, which we successfully trialed in 32 animals. (1) Background: Pancuronium bromide is a neuromuscular blocker used for immobilizing crocodiles that can be reversed with neostigmine. A recommended drug dose has only been established for saltwater crocodiles (Crocodylus porosus), mostly based on trials in juveniles and subadults. After trialing a dose recommendation in a small cohort of nine Nile crocodiles (Crocodylus niloticus), we developed and applied a new dose recommendation for large adult Nile crocodiles. (2) Methods: we trialed and adapted a pancuronium bromide (Pavulon 4 mg/2 mL) dose in Nile crocodiles originally established for saltwater crocodiles and applied the new dose for the immobilization of 32 Nile crocodiles destined for transport. Reversal was achieved with neostigmine (Stigmine 0.5 mg/mL). (3) Results: Nine crocodiles were included in the trial phase; the induction time was highly variable (average: 70 min; range: 20–143 min), and the recovery time was prolonged (average: 22 h; range: 50 min–5 days), especially in large animals after reversal with neostigmine. Based on these results, we established a dose-independent recommendation (3 mg pancuronium bromide and 2.5 mg neostigmine) for animals weighing ≥ 270 kg (TL ≥ ~3.8 m). When applied to 32 adult male crocodiles (BW range: 270–460 kg; TL range: 3.76–4.48 m), the shortest induction time was ~20 min and the longest ~45 min. (4) Conclusions: Pancuronium bromide and its antidote, neostigmine, are effective for the immobilization and reversal of adult male Nile crocodiles (TL ≥ 3.8 m or BW ≥ 270 kg) when given in a weight-independent fashion. [ABSTRACT FROM AUTHOR]

The visual ecology of early mammals remains poorly resolved. Studies of ancestral photopigments suggest an ancient transition from nocturnal to more crepuscular conditions. By contrast, the phenotypic shifts following the split of monotremes and therians—which lost their SWS1 and SWS2 opsins, respectively—are less clear. To address this, we obtained new phenotypic data on the photopigments of extant and ancestral monotremes. We then generated functional data for another vertebrate group that shares the same photopigment repertoire as monotremes: the crocodilians. By characterizing resurrected ancient pigments, we show that the ancestral monotreme underwent a dramatic acceleration in its rhodopsin retinal release rate. Moreover, this change was likely mediated by three residue replacements, two of which also arose on the ancestral branch of crocodilians, which exhibit similarly accelerated retinal release. Despite this parallelism in retinal release, we detected minimal to moderate changes in the spectral tuning of cone visual pigments in these groups. Our results imply that ancestral forms of monotremes and crocodilians independently underwent niche expansion to encompass quickly changing light conditions. This scenario—which accords with reported crepuscular activity in extant monotremes—may help account for their loss of the ultraviolet-sensitive SWS1 pigment but retention of the blue-sensitive SWS2. [ABSTRACT FROM AUTHOR]

Isolated teeth, previously referred to Aves, are more common than other bird fossils from the Late Cretaceous of Alberta. However, there are no known morphological synapomorphies that distinguish isolated bird teeth, and features of these teeth are generally shared with those of non-avian theropods and crocodilians. Here, specimens ranging from Late Santonian to Late Maastrichtian in age are described and qualitatively categorized into morphotypes, most of which strongly resemble teeth of extant juvenile and some fossil crocodilians. Variation within this sample of teeth may therefore reflect the heterodont dentition of crocodilians, rather than avian species diversity. Quantitative analysis Principal Component Analysis was mostly uninformative, with limited overlap between putative avian teeth and those of known Cretaceous birds, crocodilians, and non-avian theropods. The reassignment of these putative avian teeth to Crocodylia has important ramifications for our understanding of the evolutionary history of Cretaceous birds. [ABSTRACT FROM AUTHOR]

The Anthropocene is tightly associated with a drastic loss of species worldwide and the disappearance of their key ecosystem functions. The orders Testudines (turtles and tortoises) and Crocodilia (crocodiles, alligators, and gharials) contain numerous threatened, long-lived species for which the functional diversity and potential erosion by anthropogenic impacts remains unknown. Here, we examine 259 (69%) of the existing 375 species of Testudines and Crocodilia, quantifying their life history strategies (i.e., trade-offs in survival, development, and reproduction) from open-access data on demography, ancestry, and threats. We find that the loss of functional diversity in simulated extinction scenarios of threatened species is greater than expected by chance. Moreover, the effects of unsustainable local consumption, diseases, and pollution are associated with life history strategies. In contrast, climate change, habitat disturbance, and global trade affect species independent of their life history strategy. Importantly, the loss of functional diversity for threatened species by habitat degradation is twice that for all other threats. Our findings highlight the importance of conservation programmes focused on preserving the functional diversity of life history strategies jointly with the phylogenetic representativity of these highly threatened groups. Many species of reptiles are threatened with extinction. This analysis on 259 species of turtles, tortoises and crocodilians identifies anthropogenic threats that disproportionally affect species with certain life history strategies and others that affect all species similarly. [ABSTRACT FROM AUTHOR]

Eggshell morphology is a valuable indicator of the local conditions within the nests of modern crocodilians and birds. In contrast to these latter, the anatomical structure of the eggshells of most crocodilian species is practically unknown. Here, we provide the first characterization of crocodilian eggshells, using x-ray micro-CT scans. We studied eggshells of Caiman latirostris and Caiman yacare from various developmental stages that coincide with the beginning of embryonic ossification. The new 3D renderings revealed complex ornamentation, unique among crocodilians, and amphora-shaped pore canals, some of which converge in single pore openings. We also documented a high density of pore canals with a gas diffusion capacity 45 times higher than the average predicted for modern avian eggshells. The external ornamentation and the thickness of the compact layer of the eggshells (i.e. excluding ornamentation) showed ontogenetic and interspecific differences that could be related to nesting materials and nesting areas selected by each species. The shell features described here evidence a greater structural complexity than previously recognized in phylogenetically close, sympatric crocodilian species. Further comprehensive morphological analyses on other modern and fossil crocodilian eggshells using micro-CT technology will shed new light on the evolution of reproductive strategies in this intriguing archosaur clade. [ABSTRACT FROM AUTHOR]

Crocodilians are a taxonomic group of large predators with important ecological and evolutionary benefits for ecosystem functioning in the face of global change. Anthropogenic actions affect negatively crocodilians' survival and more than half of the species are threatened with extinction worldwide. Here, we map and explore three dimensions of crocodilian diversity on a global scale. To highlight the ecological importance of crocodilians, we correlate the spatial distribution of species with the ecosystem services of nutrient retention in the world. We calculate the effectiveness of global protected networks in safeguarding crocodilian species and provide three prioritization models for conservation planning. Our results show the main hotspots of ecological and evolutionary values are in southern North, Central and South America, west-central Africa, northeastern India, and southeastern Asia. African species have the highest correlation to nutrient retention patterns. Twenty-five percent of the world's crocodilian species are not significantly represented in the existing protected area networks. The most alarming cases are reported in northeastern India, eastern China, and west-central Africa, which include threatened species with low or non-significant representation in the protected area networks. Our highest conservation prioritization model targets southern North America, east-central Central America, northern South America, west-central Africa, northeastern India, eastern China, southern Laos, Cambodia, and some points in southeastern Asia. Our research provides a global prioritization scheme to protect multiple dimensions of crocodilian diversity for achieving effective conservation outcomes. [ABSTRACT FROM AUTHOR]

Anthropogenically induced warming is transforming Arctic ecosystems across a geologically short timescale, but earlier episodes of Earth history provide insights on the nature and limitations of biotic change in a rapidly warming Arctic. Late early Eocene strata (~52 Ma) of the Margaret Formation on Ellesmere Island, Nunavut, Canada sample a warm temperate ecosystem with a polar light regime situated at ~77°N paleolatitude. This extinct boreal ecosystem hosted a diversity of early Cenozoic vertebrates, including thermophilic taxa such as crocodilians and tapiroid perissodactyls. Here we describe two new species of the early primatomorphan Ignacius from Ellesmere, which are by far the northernmost known records for Paleogene Primatomorpha. Ellesmere species of Ignacius are sister taxa, indicating a single colonization of Ellesmere from farther south in North America coincident with the onset of the hyperthermal Early Eocene Climatic Optimum (EECO). The Ellesmere Ignacius clade differs from closely related taxa inhabiting mid-latitudes in being larger (thereby conforming to Bergmann's rule) and having modified dentition and muscles of mastication for a dietary regime emphasizing hard objects, possibly reflecting an increased reliance on fallback foods during long polar winters. The late early Eocene mammalian fauna of Ellesmere indicates that its unique paleoenvironment rendered it uninhabitable to some clades, including euprimates, while selected taxa were able to adapt to its challenging conditions and diversify. [ABSTRACT FROM AUTHOR]

Recovering populations of large carnivores impact the people that live alongside them, sometimes leading to conflict and lethal retaliation. One such carnivore, the black caiman (Melanosuchus niger) has been implicated in the destruction of fishing equipment, depredation of livestock and pets, and attacks on humans. In order to understand how various stakeholder groups are affected by the negative impacts of living alongside caiman, and their resulting attitudes and behaviors towards caiman, we conducted semistructured interviews in seven Indigenous communities in southwestern Guyana from November 2017 to October 2019. We used logistic and ordinal regression to identify demographic indicators of fishing behavior and factors that are associated with negative attitudes and antagonistic behavior. Loss of pets in addition to an effect of gender, rather than competition overfishing resources (as hypothesized) may drive conflict between Indigenous communities and black caiman. We propose site differences, such as ecotourism may affect attitudes about and behavior towards caiman. The presence of impacts on communities and retaliatory behavior indicates that human–wildlife and wildlife–human impacts involving black caiman may be a concern for the recovery of the species' populations, and the communities that coexist with them. [ABSTRACT FROM AUTHOR]

Dwarf caimans (Alligatoridae: Paleosuchus palpebrosus and Paleosuchus trigonatus), are small crocodilians exhibiting cryptic behaviour and complex habitat use that occur throughout the Amazon region. Our goals were to evaluate individual home range, habitat occupancy and movement patterns where they occur in sympatry in relation to seasonal water-level variation. We tracked five P. palpebrosus and seven P. trigonatus using VHS radio transmitters along the shores of two streams directly influenced by the flooding pulse of the Purus River. Paleosuchus palpebrosus individuals moved greater distances on a daily basis and had larger home ranges than P. trigonatus, and the species had different responses to increases in water levels. Paleosuchus palpebrosus moved into flooded forests, as do their principle prey species. Conversely, larger P. trigonatus individuals usually remained near the main stream, and were relatively sedentary. Intraspecific home-range overlap was higher than interspecific overlap in both species. Thus, habitat occupancy patterns as a function of water-level variation might facilitate coexistence of the two species of dwarf caimans in the same location. This study shows that when living in sympatry under a seasonal flooding regime, Paleosuchus species show a degree of habitat partitioning evidenced by different daily movement rates, home-range sizes and home-range locations. [ABSTRACT FROM AUTHOR]

Reptiles, the only ectothermic amniotes, employ a wide variety of physiological adaptations to adjust to their environments but remain vastly understudied in the field of immunology and ecoimmunology in comparison to other vertebrate taxa. To address this knowledge gap, we assessed the current state of research on reptilian innate immunology by conducting an extensive literature search of peer-reviewed articles published across the four orders of Reptilia (Crocodilia, Testudines, Squamata, and Rhynchocephalia). Using our compiled dataset, we investigated common techniques, characterization of immune components, differences in findings and type of research among the four orders, and immune responses to ecological and life-history variables. We found that there are differences in the types of questions asked and approaches used for each of these reptilian orders. The different conceptual frameworks applied to each group has led to a lack of unified understanding of reptilian immunological strategies, which, in turn, have resulted in large conceptual gaps in the field of ecoimmunology as a whole. To apply ecoimmunological concepts and techniques most effectively to reptiles, we must combine traditional immunological studies with ecoimmunological studies to continue to identify, characterize, and describe the reptilian immune components and responses. This review highlights the advances and gaps that remain to help identify targeted and cohesive approaches for future research in reptilian ecoimmunological studies. [ABSTRACT FROM AUTHOR]

Caiman latirostris is an opportunistic predator found in rivers, mangroves, and wetlands throughout eastern South America. We report here the predation of Tamandua tetradactyla by Caiman latirostris in an old cattle dam in the Serra da Bodoquena National Park, Brazil. The adult caiman was accompanied by its hatchlings that fed on the lacerated parts of the Lesser anteater and possibly the insects attracted by the carcass. Although Caiman latirostris acts as a fundamental organism for the balance of ecosystems, most of the species` diet records are anecdotal, making this record relevant for understanding the ecology of the species. [ABSTRACT FROM AUTHOR]

Abstract Recovering populations of large carnivores impact the people that live alongside them, sometimes leading to conflict and lethal retaliation. One such carnivore, the black caiman (Melanosuchus niger) has been implicated in the destruction of fishing equipment, depredation of livestock and pets, and attacks on humans. In order to understand how various stakeholder groups are affected by the negative impacts of living alongside caiman, and their resulting attitudes and behaviors towards caiman, we conducted semistructured interviews in seven Indigenous communities in southwestern Guyana from November 2017 to October 2019. We used logistic and ordinal regression to identify demographic indicators of fishing behavior and factors that are associated with negative attitudes and antagonistic behavior. Loss of pets in addition to an effect of gender, rather than competition overfishing resources (as hypothesized) may drive conflict between Indigenous communities and black caiman. We propose site differences, such as ecotourism may affect attitudes about and behavior towards caiman. The presence of impacts on communities and retaliatory behavior indicates that human–wildlife and wildlife–human impacts involving black caiman may be a concern for the recovery of the species' populations, and the communities that coexist with them.

Developmental oxygen is a powerful stressor that can induce morphological and functional changes in the cardiovascular systems of embryonic and juvenile vertebrates. This plasticity has been ascribed, at least in part, to the unique status of the developing cardiovascular system, which undergoes organogenesis while meeting the tissue oxygen demands of the embryo. We have previously reported an array of functional and morphological changes in embryonic American alligators that persist into juvenile life. Most notably, cardiac enlargement as well as functional parameters of anesthetized juvenile alligators remains after embryonic hypoxic exposure. Because the effects of developmental oxygen in crocodilians have only been investigated in anesthetized animals, we explored the pressure dynamics of both ventricles as well as systemic pressure in response to stressors of acute hypoxia and swimming. Our current findings demonstrate that developmental programming of cardiac function (intraventricular pressure and heart rate) does persist into juvenile life, but it is chamber-specific and depends on the experimental manipulation. Acute hypoxic exposure revealed that juvenile alligators that had experienced 10% O2 as embryos maintain right ventricle function and increase left ventricle function during exposure. Finally, the data indicate blood flow in the left aorta must originate from the left ventricle during acute hypoxia and swimming. [ABSTRACT FROM AUTHOR]

Understanding the evolution of the tetrapod brain is essential to trace the history of ecomorphological diversification of modern clades. While previous studies focused on the morphological transformation of the nervous system along the dinosaur–bird transition, little is known about the brain anatomy of archosauriformes and early archosaurs. Here, we describe the endocast of Euparkeria capensis, a small bodied, terrestrial archosauriform closely related to Archosauria, with the goal of resolving the current uncertainties surrounding the ancestral condition of the archosaurian nervous system. The endocast of Euparkeria is sigmoidal, with large olfactory bulbs, an expanded cerebral hemisphere and an elongated flocculus. We suggest that this pivotal taxon was an active predator with a remarkable olfactory acuity. Overall, the endocast of Euparkeria resembles the ones observed in phytosaurs, crocodilians and early dinosaurs, implying that modern crocodilians retain an archosaurian plesiomorphic brain morphology. [ABSTRACT FROM AUTHOR]

The gut microbiota forms a complex microecosystem in vertebrates and is affected by various factors. As a key intrinsic factor, sex has a persistent impact on the formation and development of gut microbiota. Few studies have analyzed sexual dimorphism of gut microbiota, particularly in wild animals. We used 16S rRNA gene sequencing to analyze the gut microbiota of juvenile and adult Chinese alligators, and untargeted metabolomics to study serum metabolomes of adult alligators. We observed significant sexual differences in the community diversity in juvenile, but not adult, alligators. In terms of taxonomic composition, the phylum Fusobacteriota and genus Cetobacterium were highly abundant in adult alligators, similar to those present in carnivorous fishes, whereas the gut microbiota composition in juvenile alligators resembled that in terrestrial reptiles, indicating that adults are affected by their wild aquatic environment and lack sex dimorphism in gut microbiota. The correlation analysis revealed that the gut microbiota of adults was also affected by cyanobacteria in the external environment, and this effect was sex-biased and mediated by sex hormones. Overall, this study reveals sexual differences in the gut microbiota of crocodilians and their convergence in the external environment, while also providing insights into host–microbiota interactions in wildlife. [ABSTRACT FROM AUTHOR]

Gharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers is low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nepal. The Rapti River, running across the CNP, was divided into 18 segments, each measuring ~4 km, and gharials were counted directly with three replicates. Gharial count data were analyzed using an N‐mixture model (negative binomial) and the overall occupancy of gharials was estimated using a single season occupancy model. Covariate effects were also investigated on gharial abundance. Our findings revealed that the Rapti River is home to 150 gharials (119–181), with a mean abundance of 8.3 (SD = 3.45) across each segment. The presence of humans and square of Rapti River depth were the significant covariates that had a negative and positive impact on gharial abundance, respectively. Similarly, the number of sandbank present influenced the detection probability of gharials. Our study shows that gharial population estimation can be improved using the N‐mixture model. The overall gharial occupancy estimated using single season occupancy model was 0.84 (SD = 0.08), with a detection probability of 0.37 (SD = 0.02). The management authority should concentrate on segments to minimize human disturbance (e.g., fishing, washing clothes, extraction of riverbed materials). If the gharial population in this river declines, their population in central Nepal will be threatened. Hence, we suggest designating the Rapti River section that passes across the CNP as a "no extraction zone." [ABSTRACT FROM AUTHOR]

Up to 10 males were reported to sire clutches of crocodilian eggs but review of the underlying study designs raised questions of potential upward bias of inferred sire numbers. To test this premise, different scenarios were explored using a published dataset of 16 known single‐sire saltwater crocodile pairs and their offspring which were originally confirmed using a 11 loci microsatellite panel in CERVUS. Varying the number of microsatellites, omitting one or both parental genotypes and using different parentage analysis techniques revealed that total allele number, rather than number of loci, determined inferred sire accuracy in two opposing ways. Using the single‐locus minimum method and GERUD, which both require prior knowledge of family groupings (i.e., nests), fewer alleles (and loci) accurately inferred only one father. In contrast, CERVUS and COLONY required all 11 loci (65 alleles) and both parental genotypes to (a) assign correct family groups and (b) infer the correct sire number, except in one family where two sires were equally assigned based on their number of homozygous loci. When less genotype information was provided, CERVUS and COLONY inferred up to six and seven sires, respectively. Given this data is from confirmed single‐sire matings, and yet up to seven sires could be inferred, the significance of inappropriate study design is clearly demonstrated. Consideration should be carefully given to genotype data, particularly those collected specifically for population diversity studies, which are also used to infer multiple paternity because the underlying data collection assumptions are not equivalent between the two outcomes. [ABSTRACT FROM AUTHOR]

Cranial ontogenetic variations offer information on growth and trophic ecology in Crocodilia. Therefore, we analyze the ontogenetic variations of the skull, examining the shape and some bones in C. c. fuscus. We found an allometric effect and shape changes, varying from a longirostrine skull in hatchlings to a brevirostrine one in subadults and adults. A thickening in the base of the squamosal, the quadratojugal, the lateral process of the pterygoids, the retroarticular process of the articular, and the development of a dorsal crest in the surangular were observed. These changes would probably be related to variations in diet during ontogeny, with implications that must be considered in the study of evolution and conservation of those subspecies. [ABSTRACT FROM AUTHOR]

Chlamydia spp are reported to causes systemic disease in a variety of hosts worldwide including few reports in crocodilians. Disease presentations vary from asymptomatic to fulminant disease, some of which are zoonotic. The aim of this study was to describe the pathological, immunohistochemical, and molecular findings associated with the occurrence of a previously unreported Chlamydia sp infection causing a major mortality event in farmed American alligators (Alligator mississippiensis). The outbreak presented with sudden death in juvenile alligators mainly associated with necrotizing hepatitis and myocarditis, followed by the occurrence of conjunctivitis after the initial high mortality event. The widespread inflammatory lesions in multiple organs correlated with intralesional chlamydial organisms identified via immunohistochemistry and confirmed by 23S rRNA-specific real-time quantitative polymerase chain reaction (qPCR) for Chlamydiaceae bacteria. By sequencing and phylogenetic analysis of the OmpA gene, this uncultured Chlamydia sp grouped closely with Chlamydia poikilothermis recently described in snakes. This study highlights the significance of such outbreaks in farmed populations. Enhanced epidemiological monitoring is needed to gain further insight into the biology of Chlamydia sp in alligators, disease dynamics, risk factors, and role of carrier animals. [ABSTRACT FROM AUTHOR]

Ambient noise is a major constraint on acoustic communication in both animals and humans. One mechanism to overcome this problem is Spatial Release from Masking (SRM), the ability to distinguish a target sound signal from masking noise when both sources are spatially separated. SRM is well described in humans but has been poorly explored in animals. Although laboratory tests with trained individuals have suggested that SRM may be a widespread ability in vertebrates, it may play a limited role in natural environments. Here we combine field experiments with investigations in captivity to test whether crocodilians experience SRM. We show that 2 species of crocodilians are able to use SRM in their natural habitat and that it quickly becomes effective for small angles between the target signal source and the noise source, becoming maximal when the angle exceeds 15∘. Crocodiles can therefore take advantage of SRM to improve sound scene analysis and the detection of biologically relevant signals. The ability to separate target sound signals from masking noise is identified in wild and captive crocodilian species. [ABSTRACT FROM AUTHOR]

Reptile populations are in decline globally, with total reptile abundance halving in the past half century, and approximately a fifth of species currently threatened with extinction. Research on reptile distributions, population trends, and trophic interactions can greatly improve the accuracy of conservation listings and planning for species recovery, but data deficiency is an impediment for many species. Environmental DNA (eDNA) can detect species and measure community diversity at diverse spatio‐temporal scales, and is especially useful for detection of elusive, cryptic, or rare species, making it potentially very valuable in herpetology. We aim to summarize the utility of eDNA as a tool for informing reptile conservation and management and discuss the benefits and limitations of this approach. A literature review was conducted to collect all studies that used eDNA and focus on reptile ecology, conservation, or management. Results of the literature search are summarized into key discussion points, and the review also draws on eDNA studies from other taxa to highlight methodological challenges and to identify future research directions. eDNA has had limited application to reptiles, relative to other vertebrate groups, and little use in regions with high species richness. eDNA techniques have been more successfully applied to aquatic reptiles than to terrestrial reptiles, and most (64%) of studies focused on aquatic habitats. Two of the four reptilian orders dominate the existing eDNA studies (56% Testudines, 49% Squamata, 5% Crocodilia, 0% Rhynchocephalia). Our review provides direction for the application of eDNA as an emerging tool in reptile ecology and conservation, especially when it can be paired with traditional monitoring approaches. Technologies associated with eDNA are rapidly advancing, and as techniques become more sensitive and accessible, we expect eDNA will be increasingly valuable for addressing key knowledge gaps for reptiles. [ABSTRACT FROM AUTHOR]

A checklist of herpetofauna of Telangana, India including accepted English name, scientific name along with authority, Telugu and vernacular name, IUCN, Indian Wildlife Protection Act and CITES status, and endemicity is presented in this paper. The herpetofauna diversity of Telangana is represented by 98 species including 16 species of amphibians belonging to four families, one species of crocodile, six species of testudines, 35 species of saurians and 40 species of snakes. Three species-Hemidactylus flavicaudus, H. xericolus, and H. aemulus-are endemic to Telangana. [ABSTRACT FROM AUTHOR]

(1) Background: Pancuronium bromide is a neuromuscular blocker used for immobilizing crocodiles that can be reversed with neostigmine. A recommended drug dose has only been established for saltwater crocodiles (Crocodylus porosus), mostly based on trials in juveniles and subadults. After trialing a dose recommendation in a small cohort of nine Nile crocodiles (Crocodylus niloticus), we developed and applied a new dose recommendation for large adult Nile crocodiles. (2) Methods: we trialed and adapted a pancuronium bromide (Pavulon 4 mg/2 mL) dose in Nile crocodiles originally established for saltwater crocodiles and applied the new dose for the immobilization of 32 Nile crocodiles destined for transport. Reversal was achieved with neostigmine (Stigmine 0.5 mg/mL). (3) Results: Nine crocodiles were included in the trial phase; the induction time was highly variable (average: 70 min; range: 20–143 min), and the recovery time was prolonged (average: 22 h; range: 50 min–5 days), especially in large animals after reversal with neostigmine. Based on these results, we established a dose-independent recommendation (3 mg pancuronium bromide and 2.5 mg neostigmine) for animals weighing ≥ 270 kg (TL ≥ ~3.8 m). When applied to 32 adult male crocodiles (BW range: 270–460 kg; TL range: 3.76–4.48 m), the shortest induction time was ~20 min and the longest ~45 min. (4) Conclusions: Pancuronium bromide and its antidote, neostigmine, are effective for the immobilization and reversal of adult male Nile crocodiles (TL ≥ 3.8 m or BW ≥ 270 kg) when given in a weight-independent fashion.

In the last years, lipid physiology has become an important research target for systems biology applied to the field of ecotoxicology. Lipids are not only essential components of biological membranes, but also participate in extra and intracellular signaling processes and as signal transducers and amplifiers of regulatory cascades. Particularly in sauropsids, lipids are the main source of energy for reproduction, growth, and embryonic development. In nature, organisms are exposed to different stressors, such as parasites, diseases and environmental contaminants, which interact with lipid signaling and metabolic pathways, disrupting lipid homeostasis. The system biology approach applied to ecotoxicological studies is crucial to evaluate metabolic regulation under environmental stress produced by xenobiotics. In this review, we cover information of molecular mechanisms that contribute to lipid metabolism homeostasis in sauropsids, specifically in crocodilian species. We focus on the role of lipid metabolism as a powerful source of energy and its importance during oocyte maturation, which has been increasingly recognized in many species, but information is still scarce in crocodiles. Finally, we highlight priorities for future research on the influence of environmental stressors on lipid metabolism, their potential effect on the reproductive system and thus on the offspring, and their implications on crocodilians conservation. [Display omitted] [ABSTRACT FROM AUTHOR]

Supplementation of wild populations of the Critically Endangered Gharial Gavailis gangeticus with individuals reared in captivity is a widely used conservation management tool in Nepal and India, although its efficacy is uncertain. Measuring post-release growth in Gharial can provide valuable information on acclimation of captive-reared Gharial to the wild and provide growth rates to inform population recovery models. We studied post-release growth of Gharial reared in the Gharial Conservation Breeding Centre, Nepal, following their release into the Chitwan National Park. We used recapture data from known individuals to determine growth and change of mass for 26 Gharial recaptured 0.5-10 years after release. We found that Gharial recaptured two or more years post-release had increased in mass and length despite being over six years old at release, however there was a triangular relationship between time since release and growth: some Gharial had grown very slowly, whilst others had grown much faster. All Gharial recaptured less than two years since release had lost mass and had negligible growth in total length. This data show that there is considerable variation in postrelease growth rates, which will lead to some individuals being very old before they reach a potentially mature size class, with unknown implications for reproduction. This variation is important for predicting or modelling recovery in populations where the release of Gharial from captivity is a management tool. Our results also suggest the two years after release are an acclimation phase--when Gharial lose mass and do not grow--which should be considered by release strategies in order to give Gharial the best chance of survival after release. [ABSTRACT FROM AUTHOR]

The extinct freshwater choristoderan reptiles Champsosaurus and Simoedosaurus are characterised by large body size and an elongated snout. They have often been considered as eco‐analogues of crocodilians based on superficial similarities. The slender‐snouted Champsosaurus has been described as a 'gavial‐like reptile', which implies it feeds underwater with a lateral swipe of the head and neck, as in the living slender‐snouted crocodilians such as Gavialis gangeticus. In contrast, the short‐snouted Simoedosaurus is often compared with short‐snouted living crocodilians and is considered to take single prey items. However, the neck mobility and flexibility needed for feeding movements are poorly understood even in extant crocodilians. This study explores the relationship between cervical morphology and neck flexion, focusing particularly on lateral and dorsal movements in G. gangeticus by comparison with shorter‐snouted crocodilians. The paper also describes a method to estimate the maximum angle of neck dorsiflexion in choristoderes based on the cervical morphology of extant crocodilian species. Three indices were used in this study, of which Index 3 is newly proposed, to compare cervical morphology and intervertebral joint flexibility: (1) Enclosed zygapophyseal angles (EZA) as an index of dorsoventral/ bilateral flexibility, (2) moment arm (M) of dorsiflexor muscles as an Index of resistance against ventroflexion and (3) the orientations of zygapophysial facets for a maximum angle of dorsiflexion. These Indices were validated using µCT scanning of fresh specimens of G. gangeticus and Caiman latirostris in lateral and dorsal flexion. A unique mechanism of lateral flexion was identified in G. gangeticus that uses a combination of the following features: (1) lateral flexion mainly restricted to the anterior cervical vertebrae (v2/v3: high EZA, with more horizontal zygapophyses) and (2) high degree of dorsiflexion at the v3/v4 and v4/v5 joints with potential for dorsal flexibility through the middle‐posterior neck, which is used in inertial feeding. In contrast, Champsosaurus and Simoedosaurus possess relatively short cervical vertebrae, as in short‐snouted crocodilians. The middle‐posterior cervical vertebrae of Champsosaurus are specialised for lateral flexion (high EZA), and there is only limited capacity for dorsiflexion throughout the neck. Like G. gangeticus, therefore, Champsosaurus may have used its slender snout to grab fish from shoals using lateral sweeping motions of the head and neck, but the movement is through the neck, not the craniocervical joint. However, inertial feeding is less likely to have occurred in this genus, and the aligned palatal dentition may have aided the lingual transport of prey into the mouth. Simoedosaurus, on the other hand, appears to have been less specialised, with a neck that combined lateral and dorsolateral flexion, a move that could have been effective in catching both terrestrial and aquatic prey. Where these two choristoderan genera occurred in the same place, they may have divided their niche by prey types. [ABSTRACT FROM AUTHOR]