Crocodylus Porosus Research Articles

Evaluation of a commercial electrical stunning method for farmed grower saltwater crocodiles (Crocodylus porosus) using non-invasive EEG measurements.

The aim of this study was to assess welfare outcomes of electrical stunning as a means of restraint in farmed grower saltwater crocodiles (Crocodylus porosus). Physical handling of a stunned, unconscious crocodile is far safer for the operator than handling a fully conscious animal. Electroencephalogram (EEG) was recorded before and after the application of electrical stunning at 50 Hz or 400 Hz using an electrical stunner applied to the cranial plate (Position 1: P1-50 Hz; n = 31, P1-400 Hz; n = 29) or immediately behind the skull (Position2: P2-50 Hz; n = 29; P2-400 Hz; n = 30). For all electrical stuns, percentage total EEG power in a 10-s epoch decreased in the alpha and beta frequency bands; and increased in the delta and lower frequencies bands. All electrical stuns resulted in increased strength of signal, based on the quadratic mean EEG power in all frequency bands of the EEG. Greatest change in power occurred in the delta frequency band, with P1-50 Hz. This was greater than with P2-50 Hz; while decibel change using 400 Hz at either position was intermediate and not significantly different from either. Application of either electrical stunner at position 1 resulted in seizure-like activity and activation in low frequencies, but at position 2 this was not consistent across all animals. The ability of the electrical stunning equipment to consistently induce recoverable unconsciousness could be ranked in decreasing order as: P1-50 Hz > P1-400 Hz = P2-50 Hz > P2-400 Hz. Based on behavioural observations, all animals in the study appeared to stunned however evaluation of duration of EEG changes indicates that use of the electrical stunning equipment at 50 Hz would allow some margin for inaccuracies in tong placement, while achieving a consistently reliable stun.

Population and Habitat Characteristics of the Saltwater Crocodile (Crocodylus porosus, Schneider 1801) in the Antan River, Jebus-Parittiga District, West Bangka

Saltwater crocodile (Crocodylus porosus) is the largest and longest crocodilian species in the world. The increasing human activities along river have been caused habitat degradation in watersheds. On the other hand, the crocodile population may have increased after decades of protection. Rivers that are habitat for crocodiles and have increased human occupancy have led to increase conflicts with crocodiles. This increasing cases requires the management authorities to immediately issue policies based on scientific data. Population data and habitat characteristics of saltwater crocodiles in the Bangka Belitung Islands are not yet available. The research with the aim to know the population condition and habitat characteristics of the saltwater crocodile in the Antan River, Bangka Belitung Islands, was conducted using visual encounter survey method along 5 km. Observations were made in three time periods, namely morning, afternoon, and evening with 8 repetitions per period. Population were analyzed using the encounter rate formula, while the habitat characteristics were described descriptively. During the research, we only found one adult and this individual was sighted in the morning, afternoon and evening. This study also confirms that crocodile surveys should be conducted at night. The encounter rate at the study site was 1.13 individu/km. This value indicates that the population is small. The habitat type in the Antan river is a mangrove ecosystem with a depth of around 2.55 meters, water brightness 38.6%, water temperature 29.18℃, salt content 0.89%, and water pH 6.09. Although only one adult individual is found, it requires attention because in general conflict cases occur in adult individuals.

The return of the kinga (saltwater crocodile): Population ‘bust then boom’ shapes shifting baselines in Indigenous biocultural knowledge in northern Australia

The saltwater crocodile (Crocodylus porosus) can be regarded as a cultural keystone species for many Indigenous societies around the world, including for many Aboriginal clans in northern Australia. Here the regional population of Crocodylus porosus suffered a decline, almost to extinction, with unregulated commercial hunting between the 1940s to the early 1970s. Following protected status, saltwater crocodile populations made a rapid recovery. This research documents the perceptions and experiences of this rapid (within living memory) ‘bust then boom’ saltwater crocodile population change, among a regional group of Indigenous Australians (comprising several clans) from the Alligator Rivers Region of western Arnhem Land and Kakadu National Park in the Northern Territory. Using semi-structured interviews, archival work and on-Country (place-based) learning, significant influences on the continuity of Aboriginal people's contemporary engagement with freshwater Country were identified. In particular, the loss of access to freshwater customary harvesting sites and to key harvested species, and as a driver of adaptive changes in harvesting methods and consumption preferences for saltwater crocodile meat and eggs. Importantly, the experiential losses from restricted access to waterbodies were found to have significant impact on opportunities for inter-generational knowledge transmission, according with more recent applications of the Shifting Baseline Syndrome to Indigenous Ecological Knowledge. Findings demonstrate the need for monitoring and management programs of cultural keystone species, like the saltwater crocodile, to include Indigenous-led biocultural knowledge programs as a means of supporting local and Indigenous Knowledge systems. This is particularly critical in cross-cultural, First Nations, and joint-management contexts.

Exploring market-based wildlife trade dynamics in Bangladesh

AbstractWildlife markets are hotspots for illegal wildlife trade, with traders operating as a result of weak monitoring and law enforcement. Knowledge of species traded, sources, and routes used for transport is needed to identify illegal wildlife trade markets and intervene to stem trade. We conducted surveys in 13 wildlife markets across Bangladesh every month during January-December 2019 to assess the abundance and diversity of wildlife taxa traded and the factors driving this trade. Passeriformes, Columbiformes, Psittaciformes, Artiodactyla, Carnivora and Testudines were the most traded orders. Wildlife markets were also centres of trade for high-value species, including the tigerPanthera tigris, crocodileCrocodylus porosusand tortoises. In hill markets and peri-urban markets the most commonly sold species originated from nearby forests, whereas urban markets included both native species and exotic species sourced internationally. Market type, road links to the market, the presence of law enforcement agencies, proximity to a port and form of sale (live animals or byproducts) all significantly influenced what is being traded. Trade of mammals, reptiles, high-value wildlife species and threatened species was less common in markets proximal to law enforcement agencies. Markets close to seaports or airports were more likely to sell mammals, threatened species and high-value wildlife. Based on our results, we recommend a set of interventions to help reduce market-based wildlife trade in Bangladesh.

On the estimation of body mass in temnospondyls: a case study using the large‐bodied Eryops and Paracyclotosaurus

AbstractTemnospondyli are a morphologically varied and ecologically diverse clade of tetrapods that survived for over 200 million years. The body mass of temnospondyls is a key variable in inferring their ecological, physiological and biomechanical attributes. However, estimating the body mass of these extinct creatures has proven difficult because the group has no extant descendants. Here we apply a wide range of body mass estimation techniques developed for tetrapods to the iconic temnospondyls Paracyclotosaurus davidi and Eryops megacephalus. These same methods are also applied to a collection of extant organisms that serve as ecological and morphological analogues. These include the giant salamanders Andrias japonicus and Andrias davidianus, the tiger salamander Ambystoma tigrinum, the California newt Taricha torosa and the saltwater crocodile, Crocodylus porosus. We find that several methods can provide accurate mass estimations across this range of living taxa, suggesting their suitability for estimating the body masses of temnospondyls. Based on this, we estimate the mass of Paracyclotosaurus to have been between 159 and 365 kg, and that of Eryops between 102 and 222 kg. These findings provide a basis for examining body size evolution in this clade across their entire temporal span.

The Cytogenetic Map of the Nile Crocodile (Crocodylus niloticus, Crocodylidae, Reptilia) with Fluorescence In Situ Localization of Major Repetitive DNAs.

Tandemly arranged and dispersed repetitive DNA sequences are important structural and functional elements that make up a significant portion of vertebrate genomes. Using high throughput, low coverage whole genome sequencing followed by bioinformatics analysis, we have identified seven major tandem repetitive DNAs and two fragments of LTR retrotransposons in the genome of the Nile crocodile (Crocodylus niloticus, 2n = 32). The repeats showed great variability in structure, genomic organization, and chromosomal distribution as revealed by fluorescence in situ hybridization (FISH). We found that centromeric and pericentromeric heterochromatin of C. niloticus is composed of previously described in Crocodylus siamensis CSI-HindIII and CSI-DraI repetitive sequence families, a satellite revealed in Crocodylus porosus, and additionally contains at least three previously unannotated tandem repeats. Both LTR sequences identified here belong to the ERV1 family of endogenous retroviruses. Each pericentromeric region was characterized by a diverse set of repeats, with the exception of chromosome pair 4, in which we found only one type of satellite. Only a few repeats showed non-centromeric signals in addition to their centromeric localization. Mapping of 18S-28S ribosomal RNA genes and telomeric sequences (TTAGGG)n did not demonstrate any co-localization of these sequences with revealed centromeric and pericentromeric heterochromatic blocks.

Identification of free-ranging mugger crocodiles by applying deep learning methods on UAV imagery

Individual identification contributes significantly towards investigating behavioral mechanisms of animals and understanding underlying ecological principles. Most studies employ invasive procedures for individually identifying organisms. In recent times, computer-vision techniques have served as an alternative to invasive methods. However, these studies primarily rely on user input data collected from captivity or from individuals under partially restrained conditions. Challenges in collecting data from free-ranging individuals are higher when compared to captive populations. However, the former is a far more important priority for real-world applications. In this paper, we used Unmanned Aerial Vehicle (UAV) to collect data from free-ranging mugger crocodiles, Crocodylus palustris. We applied convolutional neural networks (CNNs) to individually identify muggers based on their dorsal scute patterns. The CNN model was trained on a data set of 88,000 images focusing on the mugger's dorsal body. The data was collected from 143 individuals across 19 different locations along the western part of India. We trained two CNN models, one with an annotated bounding box approach, the YOLO-v5l, and another without annotations, the Inception-v3. We used two parameters, True Positive Rate (TPR) and True Negative Rate (TNR), to validate the efficiency of the trained models. Using YOLO-v5l, TPR (re-identification of trained muggers) and TNR (differentiating untrained muggers as ‘unknown’) values at the 0.84 decision threshold were 88.8% and 89.6%, respectively. The trained model showed 100% TNR for the non-mugger species, the Gharial, Gavialis gangeticus, and the Saltwater crocodile, Crocodylus porosus. The performance of the CNN model was reliable and accurate while using only 125 images per individual for training purposes. Inception-v3 underperformed for both the parameters, thus, showing that a bounding box approach (YOLO-v5l model) with background elimination is a promising method to individually identify free-ranging mugger crocodiles. Our manuscript demonstrates that UAV imagery appears to be a promising tool for non-invasive collection of data from free-ranging populations. It can be used to train open-source algorithms for individual identification. Further, the identification method is entirely based upon dorsal scute patterns, which can be applied to different crocodilian species, as well.

How many fathers? Study design implications when inferring multiple paternity in crocodilians.

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.

The Mangrove Density, Diversity, and Environmental Factors as Important Variables to Support the Conservation Program of Essential Ecosystem Area in Muara Kali Ijo, Pantai Ayah, Kebumen

The planning of wetland essential ecosystem area (EEA) conservation and preservation activities is important to support ecosystem stability, including the mangrove ecosystem. These activities should consider the ecological, economic, and social aspects. This study aimed to analyze the indicator of the mangrove ecosystem to support the planning program of EEA conservation in Muara Kali Ijo, Pantai Ayah, Kebumen. The research method used the mapping and planning analysis of the EEA conservation program using the indicator of mangrove density, mangrove diversity, and environmental indicators. The results showed that mangrove density in Muara Kali Ijo was 1,500-4,300 trees/ha (moderate to very dense) and was dominated by Rhizophora mucronata and Rhizophora styllosa. The potential of total dissolved solids, water salinity, potential hydrogen, dissolved oxygen, biological oxygen demand, and nitrate had a good condition to support the mangrove’s life and growth. The ecosystem essential planning also had activity to conserve and preserve the Crocodylus porosus. The planning of ecosystem essential was developed in 18.5 ha, divided into five zones: mangrove preservation area of 5.90 ha, mangrove utilization area of 6.40 ha, mangrove arboretum of 4.40 ha, mangrove rehabilitation area of 1.30 ha, and specific utilization area of 0.5 ha. The wetland EEA in Muara Kali Ijo has important value in preserving the area from coastal disaster and increasing economic value with tourism and other activities. Keywords: Crocodylus porosus preservation, essential ecosystem conservation, mangrove zonation, Muara Kali Ijo, wetland conservation

In silico prediction of the animal susceptibility and virtual screening of natural compounds against SARS-CoV-2: Molecular dynamics simulation based analysis.

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus. It has six open reading frames (orf1ab, orf3a, orf6, orf7a, orf8, and orf10), a spike protein, a membrane protein, an envelope small membrane protein, and a nucleocapsid protein, out of which, orf1ab is the largest ORF coding different important non-structural proteins. In this study, an effort was made to evaluate the susceptibility of different animals against SARS-CoV-2 by analyzing the interactions of Spike and ACE2 proteins of the animals and propose a list of potential natural compounds binding to orf1ab of SARS-CoV-2. Here, we analyzed structural interactions between spike proteins of SARS-CoV-2 and the ACE2 receptor of 16 different hosts. A simulation for 50 ns was performed on these complexes. Based on post-simulation analysis, Chelonia mydas was found to have a more stable complex, while Bubalus bubalis, Aquila chrysaetos chrysaetos, Crocodylus porosus, and Loxodonta africana were found to have the least stable complexes with more fluctuations than all other organisms. Apart from that, we performed domain assignment of orf1ab of SARS-CoV-2 and identified 14 distinct domains. Out of these, Domain 3 (DNA/RNA polymerases) was selected as a target, as it showed no similarities with host proteomes and was validated in silico. Then, the top 10 molecules were selected from the virtual screening of ∼1.8 lakh molecules from the ZINC database, based on binding energy, and validated for ADME and toxicological properties. Three molecules were selected and analyzed further. The structural analysis showed that these molecules were residing within the pocket of the receptor. Finally, a simulation for 200 ns was performed on complexes with three selected molecules. Based on post-simulation analysis (RMSD, RMSF, Rg, SASA, and energies), the molecule ZINC000103666966 was found as the most suitable inhibitory compound against Domain 3. As this is an in silico prediction, further experimental studies could unravel the potential of the proposed molecule against SARS-CoV-2.

MEDIA CONTENT ANALYSIS OF HUMAN-PREDATOR INTERACTION IN INDONESIA

Media reports on human-predator interaction can influence public attitudes and supports toward wildlife conservation. Negative interactions between humans and wildlife in Indonesia are dominated by two predator species: Sumatran tiger (Panthera tigris sumatrae) and saltwater crocodile (Crocodylus porosus). This research aims to characterize the patterns of media reporting on human-predator interaction and compare the reporting between tiger and crocodile. Media reports published between 2017-2019 were collected from online mass media using Google News searching tool. Four parameters were used to evaluate the media content: tone, framing, illustration, and objectivity. Reports on human-tiger interaction (HTI; 356 articles) and human-crocodile interaction (HCI; 430 articles) showed similar patterns including dominant negative headline tone, neutral reporting focusing on interaction events, use of neutral-safe illustrations, and objective reporting. Further investigation showed that some aspects of media reporting on HCI differed from HTI. Reporting on HTI incidents used more negative contents and illustrations; and was not as comprehensive as HTI reporting. To promote balanced reporting, this research recommends collaboration between practitioners, scientists, and media to increase the media awareness on human-predator interactions and wildlife conservation; to write engaging content; and to increase the roles of practitioners and scientists as writers and sources in mass media.

Nucleic Acid Preservation Card Surveillance Is Effective for Monitoring Arbovirus Transmission on Crocodile Farms and Provides a One Health Benefit to Northern Australia

The Kunjin strain of West Nile virus (WNVKUN) is a mosquito-transmitted flavivirus that can infect farmed saltwater crocodiles in Australia and cause skin lesions that devalue the hides of harvested animals. We implemented a surveillance system using honey-baited nucleic acid preservation cards to monitor WNVKUN and another endemic flavivirus pathogen, Murray Valley encephalitis virus (MVEV), on crocodile farms in northern Australia. The traps were set between February 2018 and July 2020 on three crocodile farms in Darwin (Northern Territory) and one in Cairns (North Queensland) at fortnightly intervals with reduced trapping during the winter months. WNVKUN RNA was detected on all three crocodile farms near Darwin, predominantly between March and May of each year. Two of the NT crocodile farms also yielded the detection of MVE viral RNA sporadically spread between April and November in 2018 and 2020. In contrast, no viral RNA was detected on crocodile farms in Cairns during the entire trapping period. The detection of WNVKUN and MVEV transmission by FTATM cards on farms in the Northern Territory generally correlated with the detection of their transmission to sentinel chicken flocks in nearby localities around Darwin as part of a separate public health surveillance program. While no isolates of WNVKUN or MVEV were obtained from mosquitoes collected on Darwin crocodile farms immediately following the FTATM card detections, we did isolate another flavivirus, Kokobera virus (KOKV), from Culex annulirostris mosquitoes. Our studies support the use of the FTATM card system as a sensitive and accurate method to monitor the transmission of WNVKUN and other arboviruses on crocodile farms to enable the timely implementation of mosquito control measures. Our detection of MVEV transmission and isolation of KOKV from mosquitoes also warrants further investigation of their potential role in causing diseases in crocodiles and highlights a “One Health” issue concerning arbovirus transmission to crocodile farm workers. In this context, the introduction of FTATM cards onto crocodile farms appears to provide an additional surveillance tool to detect arbovirus transmission in the Darwin region, allowing for a more timely intervention of vector control by relevant authorities.

Histological determination of skin thickness in farmed Australian Crocodylus porosus

This descriptive study examined the variation in ventral Crocodylus porosus (saltwater crocodile) belly skin. The study is the first to determine both intra and inter variation of C. porosus skin, epidermis and dermis thickness across the ventral belly region. Standardised ventral scales from across the belly region of a Hatchling (< 12months), Yearling (1–2 years) and Grow Out (>2 years) animals were examined using histological measurements for the stratum (s.) corneum, a combined measure for the remainder of the epidermis; the s. granulosum, s. spinosum and s. basale, and the dermis. This study determined that there was a thinning across all layers of the belly skin, from the head to the cloaca, and a decrease in thickness scales in lateral scales compared to midline scales. Variation within a scale was found predominately in the s. corneum and can be related to the change in keratin type from beta- to alpha- in the hinge (inter-scalar) region and the integumentary sensory organs. Future studies should utilise a larger sample size and consider less invasive imaging techniques.

The Media Verification of Hoaxes about Human-Crocodile Conflicts

The human-crocodile conflict frequently happens in Indonesia. Based on the data from http://www.crocodile-attack.info/, it is claimed that Indonesia is a country with the most cases of crocodile attacks. Mostly the attacks involved the saltwater crocodile (Crocodylus porosus). On the other hand, this conflict is worsened by the spread of inaccurate information among communities. From October 2019 to October 2021, there were 12 false stories about crocodile attacks. These hoaxes were distributed on social media, causing fear to those who consumed the information. It is crucial to be investigated, especially from the perspective of environmental journalism. This study describes how mainstream media outlets tried to clarify the hoaxes. The results show many materials contained by information disorder, which need to be clarified by the media to ensure clarity and truth for the public. This study finds that most mainstream media still have their conscience to protect the public from false information. It was done by practicing curation journalism that includes the discipline of verification. In conclusion, the media and information sources need to have a good comprehension of crocodile behavior. The research also catches the need for environmental journalism training for media practitioners in Indonesia. Thus, the media will be able to offer the best solution for reducing the attack while at the same time giving adequate education for the public to live in harmony with Indonesian flora and fauna.

Evidence of Infection with Zoonotic Mosquito-Borne Flaviviruses in Saltwater Crocodiles (Crocodylus porosus) in Northern Australia.

The risk of flavivirus infections among the crocodilian species was not recognised until West Nile virus (WNV) was introduced into the Americas. The first outbreaks caused death and substantial economic losses in the alligator farming industry. Several other WNV disease episodes have been reported in crocodilians in other parts of the world, including Australia and Africa. Considering that WNV shares vectors with other flaviviruses, crocodilians are highly likely to also be exposed to flaviviruses other than WNV. A serological survey for flaviviral infections was conducted on saltwater crocodiles (Crocodylus porosus) at farms in the Northern Territory, Australia. Five hundred serum samples, collected from three crocodile farms, were screened using a pan-flavivirus-specific blocking ELISA. The screening revealed that 26% (n = 130/500) of the animals had antibodies to flaviviruses. Of these, 31.5% had neutralising antibodies to WNVKUN (Kunjin strain), while 1.5% had neutralising antibodies to another important flavivirus pathogen, Murray Valley encephalitis virus (MVEV). Of the other flaviviruses tested for, Fitzroy River virus (FRV) was the most frequent (58.5%) in which virus neutralising antibodies were detected. Our data indicate that farmed crocodiles in the Northern Territory are exposed to a range of potentially zoonotic flaviviruses, in addition to WNVKUN. While these flaviviruses do not cause any known diseases in crocodiles, there is a need to investigate whether infected saltwater crocodiles can develop a viremia to sustain the transmission cycle or farmed crocodilians can be used as sentinels to monitor the dynamics of arboviral infections in tropical areas.

Environmental DNA analysis confirms extant populations of the cryptic Irwin\u2019s turtle within its historical range

BackgroundApproximately 50% of freshwater turtles worldwide are currently threatened by habitat loss, rural development and altered stream flows. Paradoxically, reptiles are understudied organisms, with many species lacking basic geographic distribution and abundance data. The iconic Irwin’s turtle, Elseya irwini, belongs to a unique group of Australian endemic freshwater turtles capable of cloacal respiration. Water resource development, increased presence of saltwater crocodiles and its cryptic behaviour, have made sampling for Irwin’s turtle in parts of its range problematic, resulting in no confirmed detections across much of its known range for > 25 years. Here, we used environmental DNA (eDNA) analysis for E. irwini detection along its historical and contemporary distribution in the Burdekin, Bowen and Broken River catchments and tributaries. Five replicate water samples were collected at 37 sites across those three river catchments. Environmental DNA was extracted using a glycogen-aided precipitation method and screened for the presence of E. irwini through an eDNA assay targeting a 127 base pair-long fragment of the NADH dehydrogenase 4 (ND4) mitochondrial gene.ResultsElseya irwini eDNA was detected at sites within its historic distribution in the lower Burdekin River, where the species had not been formally recorded for > 25 years, indicating the species still inhabits the lower Burdekin area. We also found higher levels of E. iriwni eDNA within its contemporary distribution in the Bowen and Broken Rivers, matching the prevailing scientific view that these areas host larger populations of E. irwini.ConclusionsThis study constitutes the first scientific evidence of E. irwini presence in the lower Burdekin since the original type specimens were collected as part of its formal description, shortly after the construction of the Burdekin Falls Dam. From the higher percentage of positive detections in the upper reaches of the Broken River (Urannah Creek), we conclude that this area constitutes the core habitat area for the species. Our field protocol comprises a user-friendly, time-effective sampling method. Finally, due to safety risks associated with traditional turtle sampling methods in the Burdekin River (e.g., estuarine crocodiles) we propose eDNA sampling as the most pragmatic detection method available for E. irwini.

Crocodylus porosus Sera a Potential Source to Identify Novel Epigenetic Targets: In Silico Analysis.

We have previously found that sera from Crocodylus porosus contain anticancer agents and the treatment of MCF7 cells with this serum resulted in the differential expression of 51 genes. The purpose of this study was to use in silico analysis to identify genes that might be epigenetically modulated in cells treated with crocodile serum and to understand the role of potential genes as novel candidates with epigenetic therapeutic potential. The findings report five proto-oncogenes (TUBA1B, SLC2A1, PGK1, CCND1, and NCAPD2) and two tumor suppressor genes (RPLP2, RPL37) as novel therapeutic targets. Furthermore, we present a comprehensive overview of relevant studies on epigenetic regulation of these genes along with an insight into their clinical implications. Therefore, elucidating the molecules present in the serum and gut bacteria of reptiles such as crocodiles may offer insights into the role of these genes on longevity, health, disease, and life expectancy.

Lost to the Sea: Predicted Climate Change Threats to Saltwater Crocodile Nesting Habitat

Climate change is predicted to have devastating impacts on apex predators such as eliminating their required habitats. Crocodilians are no exception as most species require freshwater for nesting, and such freshwater habitats are particularly vulnerable to saltwater inundation (SWI) caused by the sea level rise (SLR) from global warming. Here, we examined the impacts of climate change on saltwater crocodiles Crocodylus porosus in terms of the potential loss of nesting habitat in the Northern Territory, Australia; an area that contains the world’s most extensive nesting habitat for the species. Our spatial model, derived from 730 nest locations and selected environmental features, estimated a total of 32,306.91 km2 of current suitable habitat across the study region. The most important variable was distance to perennial lakes (71.0% contribution, 87.5% permutation importance), which is negatively correlated with nesting habitat suitability. We found that projected changes in temperature and rainfall by 2100 could impact the area of suitable nesting habitat negatively or positively (0.33% decrease under low future emission climate scenario, and 32.30% increase under high emission scenario). Nevertheless, this can be canceled by the strong negative impact of SLR and concomitant SWI on nesting areas. A portion (16.40%) of the modeled suitable habitat for a subsection of our study area, the Kakadu Region, were already subject to &amp;gt; 0.25 m SWI in 2013. The suitable area for nesting in this region is predicted to be further reduced to 1775.70 km2 with 1.1 m SLR predicted for 2100, representing 49.81% loss between 2013 and 2100. Although the estimates of habitat loss do not account for the potential creation of new habitat, nor for the uncertainty in the degree of future SLR, our results suggest that SLR driven by continuing global warming can be the major threat to mound-nest-building crocodilians including C. porosus, rather than direct impacts from changes in temperature and rainfall. The degree of impact on saltwater crocodiles will be determined by the interplay between the loss of nesting habitat, which would appear inevitable under current global warming, and the ability to expand into new areas created by the expansion of the tropics.

Issue Cover (April 2022)

Front cover: Bony labyrinth shown in a hatching Crocodylus porosus, based on a computed tomography scan. See J.A. Schwab et al., 'Ontogenetic variation in the crocodylian vestibular system.

Dietary shifts may underpin the recovery of a large carnivore population.

Supporting the recovery of large carnivores is a popular yet challenging endeavour. Estuarine crocodiles in Australia are a large carnivore conservation success story, with the population having extensively recovered from past heavy exploitation. Here, we explored if dietary changes had accompanied this large population recovery by comparing the isotopes δ13C and δ15N in bones of crocodiles sampled 40 to 55 years ago (small population) with bones from contemporary individuals (large population). We found that δ13C and δ15N values were significantly lower in contemporary crocodiles than in the historical cohort, inferring a shift in prey preference away from marine and into terrestrial food webs. We propose that an increase in intraspecific competition within the recovering crocodile population, alongside an increased abundance of feral ungulates occupying the floodplains, may have resulted in the crocodile population shifting to feed predominantly upon terrestrial food sources. The number of feral pigs consumed to sustain and grow crocodile biomass may help suppress pig population growth and increase the flow of terrestrially derived nutrients into aquatic ecosystems. The study highlights the significance of prey availability in contributing to large carnivore population recovery.