Crocodylus Porosus Research Articles

Cooling down is as important as warming up for a large-bodied tropical reptile.

An ectotherm's performance and physiological function are strongly tied to environmental temperature, and many ectotherms thermoregulate behaviourally to reach optimum body temperatures. Tropical ectotherms are already living in environments matching their thermal tolerance range and may be expected to conform to environmental temperatures. We tracked the body temperatures (Tb) of 163 estuarine crocodiles across 13 years and compared Tb of 39 crocodiles to water temperature gathered using fish-borne sensors (Tw) across 3 years (2015-2018). While Tb largely conformed closely to Tw, we found inter- and intra-individual differences in relative body temperature (Tb-Tw) that depended on sex and body size as well as the time of day and year. Deviations from Tw, especially during the warm parts of the year, suggest that thermoregulatory behaviour was taking place: we found patterns of warming and cooling events that seemed to mediate this variation in Tb. Thermoregulatory behaviour was observed most frequently in larger individuals, with warming events common during winter and cooling events common during summer. By observing free-ranging animals across multiple years, we found that estuarine crocodiles show yearly patterns of active cooling and warming behaviours that modify their body temperature, highlighting their resilience in the face of recent climate warming. Our work also provides the first evidence for thermal type in large-bodied reptiles.

Correction to: Snowballing trends of saltwater crocodile conflicts in Andaman Islands: a mounting concern for conservation and sustainable coexistence

Correction to: Snowballing trends of saltwater crocodile conflicts in Andaman Islands: a mounting concern for conservation and sustainable coexistence

Application of chimeric antigens to paper-based diagnostics for detection of West Nile virus infections of Crocodylus porosus – A novel animal test case

Laboratory-based diagnostics such as plaque reduction neutralisation tests (PRNT) and ELISA are commonly used to detect seroconversion to flavivirus infections. However, faster, qualitative screening methods are essential for quicker diagnosis and improved patient outcomes. Lateral flow assays (LFAs) offer rapid results (5–15 mins) at the point-of-care, but few commercial flavivirus antibody detection LFAs are available.We developed an LFA using novel chimeric viral antigens produced by genetically modifying the mosquito restricted Binjari virus (BinJV) to display the outer virion proteins of pathogenic viruses like West Nile virus (WNV). The BinJV chimeric platform offers several advantages for diagnostic assay development, including rapid construction of new chimeras in response to emerging viral variants, safe, scalable antigen manufacturing, and structural indistinguishability to the wild-type pathogenic virion.To demonstrate feasibility, we applied the chimeric WNV (BinJV/WNV) antigen to LFA as the capture/test line reagent for detecting seroconversion in crocodilians to WNV – a virus affecting crocodilians across multiple continents. We confirmed the antigenic conservation of the chimera on the LFA detection surface using monoclonal antibodies. Utilising well-characterised sera (n=60) from WNV-seropositive or flavivirus-naive Australian saltwater crocodiles (Crocodylus porosus), the assay exhibited 98.8 % sensitivity and 100 % specificity, with results obtained in under 15 minutes. The LFA also accurately detected seroconversion in animals experimentally infected with WNV.This qualitative screening method can be performed both inside and outside of a laboratory, and the assay design will guide the optimisation of similar tests for detecting vector-borne viral infections in humans and other animals.

Active crocodiles are less sociable.

How animals move and associate with conspecifics is rarely random, with a population's spatial structure forming the foundation on which the social behaviours of individuals form. Studies examining the spatial-social interface typically measure averaged behavioural differences between individuals; however, this neglects the inherent variation present within individuals and how it may impact the spatial-social interface. Here, we investigated differences in among-individual (co)variance in sociability, activity and site fidelity in a population of wild estuarine crocodiles, Crocodylus porosus, across a 10-year period. By monitoring 118 crocodiles using coded acoustic transmitters and an array of fixed underwater receivers, we discovered that not only did individual crocodiles repeatably differ (among-individual variation) in each behaviour measured but also in how consistently they expressed these behaviours through time (within-individual variation). As expected, crocodile activity and sociability formed a behavioural syndrome, with more active individuals being less sociable. Interestingly, we also found that individuals that were either more sociable or displayed greater site fidelity were also more specialized (lower within-individual variation) in these behaviours. Together, our results provide important empirical evidence for the interplay between spatial, temporal and social individual-level behavioural variation and how these contribute to forming behavioural niches. This article is part of the theme issue 'The spatial-social interface: a theoretical and empirical integration'.

Understanding Socio-Ecological Complexity of Mangrove-Crocodile-Fisher System of Bugsuk Island, Balabac, Palawan, the Philippines

The mangrove forest in Palawan has the most extensive distribution in the Philippines. The fisher community's perception of the mangrove forest as a known habitat for saltwater crocodiles (Crocodylus porosus) and its fishery benefits in Bugsuk Island were gathered using a participatory systems mental modeling framework for the coastal social-ecological system. From the causal loop diagram, six reinforcing and one balancing feedback loop were derived. The respondents observed a positive growth in the interaction between mangroves and crocodiles in Bugsuk Island, with both populations expanding and providing support to fishery resources. Bugsuk Island represents a unique diversity with great potential for resource conservation and economic benefit.

Integrative paleophysiology of the metriorhynchoid Pelagosaurus typus (Pseudosuchia, Thalattosuchia).

Paleophysiology is an emergent discipline. Organismic (integrative) approaches seem more appropriate than studies focusing on the variation of specific features because traits are tightly related in actual organisms. Here, we used such an organismic approach (including lifestyle, thermometabolism, and hunting behavior) to understand the paleobiology of the lower Jurassic (Toarcian) thalattosuchian metriorhynchoid Pelagosaurus typus. First, we show that the lifestyle (aquatic, amphibious, terrestrial) has an effect on the femoral compactness profiles in amniotes. The profile of Pelagosaurus indicates that it was amphibious, with a foraging activity in shallow marine environments (as suggested by the presence of salt glands) and thermoregulatory basking behavior in land (as suggested by the presence of osteoderms with highly developed ornamentation). As for the thermometabolism, we show that the mass-independent resting metabolic rate of Pelagosaurus is relatively high compared to the sample of extant ectothermic amniotes, but analysis of vascular canal diameter and inferences of red blood cell size refute the hypothesis suggesting incipient endothermy. Finally, the foraging behavior was inferred using two proxies. Pelagosaurus had a mass-independent maximum metabolic rate and an aerobic scope higher than those measured in the almost motionless Iguana iguana, similar to those measured in the sit-and-wait predator Crocodylus porosus but lower than those quantified in the active hunter Varanus gouldii. These results suggest that Pelagosaurus may have had a hunting behavior involving a slow sustained swimming or a patient waiting in shallow waters, and may have caught preys like gharials, using fast sideways sweeping motions of the head.

Behaviours of farmed saltwater crocodiles (Crocodylus porosus) housed individually or in groups.

Saltwater crocodiles (Crocodylus porosus) are farmed in Australia primarily for their skins and meat. Commercially, they are raised in group pens as hatchlings and grower crocodiles and then moved to unitised (individual) pens for the final finishing stage when they are several years old. They will exhibit aggressive behaviour towards each other in captivity. Unitised pens can prevent animal injury and teeth marks on the skins but may result in other social restrictions. Research into behavioural housing preferences could assist the industry and inform the process of guideline development for optimal crocodile management and welfare. This study assessed the impacts of two housing systems, unitised or group pens, in 20 commercial finishing crocodiles through measuring behavioural profiles of individuals from video recordings, including housing preference when given a choice. Both pens included water and an above-water shelf, but the crocodiles in unitised pens could also access underneath the shelf. A threat perception test was applied to assess anxiety when housed individually or in groups. However, it was difficult to apply a standardised stimulus to all animals that reliably elicited a behavioural response. Further work would be needed to validate this test for commercial reptiles as the outcomes were not robust. The behavioural observation results showed clear differences in where the crocodiles spent their time across the day and in their activity levels between the pen types. However, interpretation of this variation was confounded by the physical and social differences between the pen types given the inconsistency in shelf access. Behaviours exhibited also differed given there were social opportunities in the group pens where individuals were observed engaged in both aggressive and non-aggressive contact interactions. In the free choice environment, crocodiles spent similar amounts of time in both unitised and group pens, suggesting there were features of both pen types that were attractive to the animals. However, skins were damaged from teeth marks highlighting the physical and economical risks of group housing. Further work could validate behavioural tests to quantify affective state impacts in different housing environments and whether social interactions do provide benefits for improving crocodile welfare.

Snowballing trends of saltwater crocodile conflicts in Andaman Islands: A mounting concern for conservation and sustainable co-existence

Snowballing trends of saltwater crocodile conflicts in Andaman Islands: A mounting concern for conservation and sustainable co-existence

Crocodilian Phallic Malformations and Anomalies

Abstract Phallic malformations directly impact crocodilian copulatory function and thus could impact reproductive success in individual animals. This case series characterizes malformations observed and the implied reproductive consequences. We assessed a range of phallic malformations observed in saltwater crocodile (Crocodylus porosus), Nile crocodile (Crocodylus niloticus), broad-snouted caiman (Caiman latirostris), and Cuban crocodile (Crocodylus rhombifer) during veterinary examinations or postmortem studies and characterized observation into the following categories: amputation, phallic glans malformations, sulcus spermaticus obstruction, and prolapse. Through detailed descriptions of these anomalies, we discuss potential reproductive health impact based on current knowledge across crocodilian species. When considering captive management of breeding stock, it is vital to examine individual efficacy at achieving proper intromission and insemination. Therefore, full reproductive examination in males should be part of routine examination to best manage individuals with such anomalies.

Exploring the most common lesion of Australian farmed saltwater crocodile (Crocodylus porosus) belly skin in the Northern Territory

This is the first descriptive study to characterise and identify the most common lesions on harvested Australian saltwater crocodiles (Crocodylus porosus). 88 skins were examined over a 17-month period as part of normal farming practices, 2901 lesions identified, with scale location, location of the lesion on the scale, and characteristics (contour, keratin normality, translucency and colour) recorded. The study determined that linear lesions accounted for 68.25 % of lesions followed by foci lesions 17.24 %. Lesions were distributed on the upper proportion of the belly skin (77.8 %) and along the midline (72 %). The most common lesion identified was a single translucent linear lesion across the scale that otherwise appeared normal (58.95 %). While there is extensive research into pathogenic agents, further research is recommended to explore further causation of linear lesions, and factors that may contribute to their prevention. Given the subjective nature of crocodile skin grading, it is recommended future research into lesions is required to ensure the sustainability and profitability of the industry.

The use of a penetrative captive bolt device during the killing of farmed saltwater crocodiles (Crocodylus porosus)

ABSTRACT Killing of farmed saltwater crocodiles involve stunning with a penetrative captive bolt device, followed by a cut across the nape of the neck and physical destruction of the brain to ensure death. This study was a welfare-based assessment of the use of a penetrative captive bolt device in saltwater crocodiles, to determine whether it satisfies the criteria of a humane stunning method and can be regarded as a direct killing method without the need for the application of an adjunct method. Methods used were electroencephalogram (EEG), observation of post-stun behavior, and postmortem examination of gross pathology of the cranium and brain. 30 of 30 animals, demonstrated immediate and irreversible loss of consciousness. There was extensive damage to the brain in all animals, deemed to be inconsistent with cortical function and possible recovery. The CASH Special 0.22 penetrative captive bolt pistol (1.25 grain cartridge), applied to the top of the cranial plate, produced immediate and irreversible unconsciousness in all the animals studied. This method satisfies animal welfare expectations, providing crocodile processors with a technique that contributes to a humane killing process.

Wildlife conservation through traditional values: alarming numbers of crocodile attacks reported from Timor-Leste

AbstractOn the IUCN Red List the saltwater crocodile Crocodylus porosus is categorized globally as Least Concern, with national populations ranging from fully recovered to extinct. The saltwater crocodile population of the Southeast Asian island nation of Timor-Leste was severely depleted by colonial hunting but has recovered since independence in 2002. During 2007–2014 there was a 23-fold increase in reported crocodile attacks (104 documented attacks), concomitant with a 2% annual increase in the human population. Public tolerance to attacks and the reluctance to harm crocodiles are entwined with reverence of crocodiles as sacred beings by most but not all Timorese people. In 2022, 7–8 years after our previous assessment, we visited five sites on the south coast of Timor-Leste in Lautém, Viqueque, Manufahí and Cova Lima municipalities. High rates of crocodile attacks continue. We obtained 35 records of attacks for 2015–2022 (34% fatal). In the municipalities where crocodile attacks occurred (Lautém, Viqueque, Cova Lima), the sacred status of crocodiles prevented inhabitants from harming them in retribution. In Manufahí, where no attacks were reported, such traditional values never existed and crocodiles were hunted for subsistence and to improve safety. The design of a context-specific crocodile management programme that respects the reverence attributed to crocodiles by most people but reduces the risk of people being attacked by crocodiles is a conservation management challenge for the government of Timor-Leste. The developing tourism industry, which relies on coastal beaches and reefs, is jeopardized by the risk of crocodile attacks.

New records of Hepatozoon and Oswaldofilaria from saltwater crocodiles (Crocodylus porosus) in Australia

Diseases affecting wild Australian saltwater crocodiles (Crocodylus porosus) are rarely reported due to the difficulty in capturing animals and obtaining samples. In this investigation, we identified two haemoparasites (Hepatozoon and a filarial nematode) in saltwater crocodiles in Darwin, Australia. Light microscopic examination identified Hepatozoon in 7/7 (100%) wild crocodiles and in 2/20 (10%) of captive ones. When genomic DNAs from these same samples were further investigated using polymerase chain reaction (PCR)-based sequencing, we detected Hepatozoon in all 27 blood samples. Using both microscopy and PCR-based sequencing, we detected a filarial worm (proposed to be Oswaldofilaria) in one of 20 captive crocodiles. The sequence data were compared with sequence data available in public databases, and phylogenetic analyses indicated that the operational taxonomic units of Hepatozoon and Oswaldofilaria discovered here in these crocodiles are likely new species. This study is the first to use molecular tools to explore haemoparasites in Australian saltwater crocodiles and highlights the importance of health investigations in poorly studied vertebrate hosts.

Diversity and genetic characterization of Chlamydia isolated from Siamese crocodiles (Crocodylus siamensis)

Chlamydiosis, an infection caused by several Chlamydia species, has been reported in Nile, saltwater, and Siamese crocodiles. Despite its widespread reports in various countries, including Thailand, genetic information on Chlamydia species remains limited. This study presents a whole-genome-based characterization of Siamese crocodile-isolated Chlamydia. The results showed that Siamese crocodile Chlamydia contained a single circular chromosome with a size of 1.22–1.23 Mbp and a plasmid with a size of 7.7–8.0 kbp. A plasmid containing eight coding sequences (CDSs) was grouped in a β lineage. A chromosome sequence had approximately 1,018–1,031 CDSs. Chlamydial factors involving virulence were documented in terms of the presence of cytotoxins and several virulence factors in the chromosomes of Siamese crocodile Chlamydia. The analysis of antimicrobial resistance genes in the Chlamydia genome revealed that the most common resistance genes were associated with aminoglycosides, fluoroquinolones, macrolides, tetracyclines, and cephalosporins, with loose matching (identities between 21.12 % and 74.65 %). Phylogenetic analyses, encompassing the assessments of both whole proteome and nine taxonomic markers, revealed that Siamese crocodile Chlamydia was separated into three lineages (lineages I–III) with high bootstrapping statistic support. Interestingly, isolate 12–01 differed genetically from the others, suggesting that it is a new member of Chlamydia. The study findings indicate that Siamese crocodiles are susceptible hosts to Chlamydia, involving more than one species. This study is the first employing the highest number of whole-genome data on Siamese crocodile Chlamydia and provides better insights into pathogen genetics.

A proxy for brain-to-endocranial cavity index in non-neornithean dinosaurs and other extinct archosaurs.

Although the brain fills nearly the entire cranial cavity in birds, it can occupy a small portion of it in crocodilians. The lack of data regarding the volumetric correspondence between the brain and the cranial cavity hampers thorough assessments of the degree of encephalization in non-neornithean dinosaurs and other extinct archosaurs and, consequently, informed inferences regarding their cognitive capacities. Existing data suggest that, across extant archosaurs, the degree of endocranial doming and the volume of intracranial nonneural components are inversely related. We build upon this information to develop an equation relating these two anatomical features in non-neornithean dinosaurs and other extinct archosaurs. We rely on measurements of the endocast doming and brain-to-endocranial cavity (BEC) index in extant relatives of non-neornithean dinosaurs, namely, the crurotarsans Caiman crocodilus, Crocodylus niloticus, and Crocodylus porosus; the paleognaths Struthio camelus and Apteryx mantelli; and the fowl Macrocephalon maleo, Gallus gallus, Meleagris gallopavo, Phasianus colchicus, and Anas platyrhynchos. Applying the equation to representative endocasts from major clades of dinosaurs, we found that BEC varies from about 0.6 in ceratopsians and thyreophorans to around 0.7 in ornithopods, pachycephalosaurians, sauropods, and theropods. We, therefore, warn against the use of a catch-all value, like 0.5, and instead encourage refinement in the adoption of BEC across archosaurs.

Human–crocodile interactions in the western Solomon Islands: the importance of local data for reducing attacks on people

AbstractInteractions between people and the saltwater crocodile Crocodylus porosus frequently occur on islands and in coastal regions. Saltwater crocodiles impact people's lives and livelihoods by attacking them, resulting in minor or serious injuries, and by interfering in people's foraging activities. Retaliation may include killing the crocodiles involved. To reduce such human–crocodile interactions, data about the occurrence of incidents are required. We present data on encounters with crocodiles and attacks on people in the Roviana Lagoon, Solomon Islands. Data includes time of incident, gender, age and activity of the victim, water conditions and what happened to the crocodile after the incident. We used a questionnaire to capture the details of incidents that occurred during 2000–2020 in the villages of Dunde, Baraulu, Nusa Hope and Kozou. Most incidents were in the evening, mostly involving women, and most victims were aged 20–39 years or ≥ 60 years. In all cases people were attacked while gleaning for shellfish in the mangroves. Attacks occurred irrespective of whether the water was clear or murky, and in all cases the crocodiles were not killed. Such site-specific data will facilitate the formulation of strategies for reducing negative interactions between people and crocodiles in this particular location. Although the saltwater crocodile is categorized as Least Concern on the IUCN Red List, research such as this provides data that can be used for promoting coexistence with and conservation of this species.

Short Communication: A Rapid Assessment of Vertebrate in Pasir Timbul-Sungsang IV, Banyuasin, South Sumatra, Indonesia

The mangrove forest in Pasir Timbul, Sungsang IV Village, Banyuasin Regency, part of mangrove area within the Air Telang Protected Forest Area, is experiencing pressure from changes in land cover. A rapid survey to determine the vertebrate diversity in Pasir Timbul, at the tip of the Air Telang Protected Forest area was conducted in early June 2023. The purpose of the survey is to propose species priority in conservation within context species and habitat management plan. Vertebrate surveys were carried out rapidly using several methods adapted to certain taxa levels, namely amphibians and reptiles, fish, birds and mammals. Priority for fauna conservation in the Air Telang Protected Forest (study area) for reptiles: Crocodylus porosus (Protected under Indonesian law), Fishes: Eleutheronema tetradactylum (Endangered by IUCN), Birds: Anhinga melanogaster (Protected), Haliastur indus (Protected), Microhierax fringillarius (Protected), Rhipidura javanica (Protected), and Mammals including the long-tailed macaque Macaca fascicularis (Endangered), langurs Trachypithecus cristatus (Vulnerable), and Prionailurus sp. Conservation efforts need to be increased because this area as buffer zone of Berbak Sembilang National Park, having high carbon absorption, and provide a breeding ground for fish, shrimp and crabs. It is clear the site is habitat for various fauna (including protected ones), as well as other ecological functions such as breaking waves, resisting seawater intrusion and abrasion.

Biodiversity conservation in Myanmar's coastal wetlands: Focusing on saltwater crocodile habitats and connectivity

Landscape-level conservation strategies are needed to protect the saltwater crocodile population and habitats in Myanmar. Identifying the remaining habitats and movement corridors is essential due to population decline across coastal regions and insufficient habitat coverage, even within protected areas. This study predicts the distribution of habitats and creates low-resistance corridors that facilitate movement across the landscape. Occurrence dataset encompassing a 20-year period (1999–2019) was used incorporating records gathered from the Global Biodiversity Information Facility—GBIF, crocodile counting reports from the Meinmahla Kyun wildlife sanctuary of Myanmar, and recent spotlight and camera-trap surveys. Using landscape connectivity tools, structural compositions of habitat classes were determined, and habitat patches were delineated to simulate the least-cost corridor and dispersal pathways. Two patches in Rakhine, two in Ayeyarwady and Yangon, one in Mon, and two in Tanintharyi, were identified that include 1247 km2 of core suitable habitat areas. The Ayeyarwady Delta exhibits a plethora of suitable habitats, while the Rakhine and Tanintharyi regions have higher marginal habitats that are largely unprotected. Only 12 % of the extent of occurrence of saltwater crocodiles are suitable habitats with a high potential for occupancy. Habitats are highly fragmented and four bottlenecks are identified to assist population connectivity in those fragmented patches. Despite notable challenges in ensuring connectivity to restore populations across the habitat patches, we highlighted connectivity as the foundation for establishing an ecological network of Myanmar's coastal habitats, leveraging the saltwater crocodile as an umbrella species for the region's coastal wetlands, and identifying key areas for enhanced protection.

Analysis of the Behavioral Patterns of the Flower Python (Malayopython Retikulatus) at the Indonesian Sioux Snake Foundation

Reptiles (creeping animals, Latin "reptans" meaning "crawling" or "crawling") are a group of cold-blooded vertebrates whose bodies are covered with scales. Reptiles are quadrupeds (four-legged animals) that lay eggs, the embryos of which are covered with amniotic membranes. Most reptiles are oviparous (lay eggs), but some squamate species are viviparous (give birth). Living reptiles feed their fetuses with a type of placenta similar to that of mammals. The size of reptiles varies from 1.6 cm (small gecko, Sphaerodactylus ariasae) to 6 m high and weighing 1 ton (salt water crocodile, Crocodylus porosus). The field of natural science that studies reptiles is herpetology.

Indian Saltwater crocodiles (Crocodylus porosus Schneider, 1801) and their conservation perspective

The Saltwater crocodile (Crocodylus porosus Schneider, 1801), population in India has been relatively stable. They are listed as a Schedule I species in the Wildlife Protection Act of India, which provides them with legal protection. However, several natural and anthropogenic factors are cumulatively putting significant challenges towards the successful conservation of the various populations and sub-populations of the Saltwater crocodiles in their natural habitats across India. Hence, it is important to understand the factors impacting their population decline and identifying the strategies and policies necessary for successful long term conservation of this majestic reptilian species across their natural habitats in India. The current study makes a multi perspective introspection of the successful conservation efforts of the Indian Saltwater crocodile.