Crocodile Populations Research Articles

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'.

Crocodiles of the Ouémé lower valley in Southern Benin: Local perceptions, uses and conservation challenges

The Ouémé Lower Valley, located in Southern Benin, is renowned for its rich biodiversity, which includes three species of crocodiles. Despite the presence of the crocodile species, the relation between these species and the local population is not well known. In this study, we aimed to examine local perceptions of crocodiles, document their uses, and identify conservation challenges. Over a period of 10 months, we surveyed the local population to understand their perceptions of crocodiles and the uses they make of these animals. Given the critical role of perceived threats in shaping conservation attitudes and behaviours, our objective also included analyzing perceived threats to crocodiles. From the 420 individuals interviewed, 90 % have a negative perception of crocodiles, perceiving them as harmful. However, 10 % of respondents, mainly from the 'Xwla' ethnic group, have a positive perception, perceiving crocodiles as harmless and beneficial. Local communities attribute various virtues to crocodile by-products, with crocodile teeth being the most cited, valued for their protective qualities. According to them, the decline in crocodile populations in the area is attributed primarily to poaching, agriculture, and sand extraction, as reported by 35 %, 28 %, and 22 % of respondents, respectively. Educational initiatives aimed at raising awareness about the ecological significance of crocodiles should be implemented, particularly targeting ethnic groups with negative perceptions of crocodiles in the region. Future researches are also needed in order to study in deep the impacts of anthropic activities on the crocodile population in the area.

Taste aversion training can educate free-ranging crocodiles against toxic invaders.

Apex predators play critical ecological roles, making their conservation a high priority. In tropical Australia, some populations of freshwater crocodiles (Crocodylus johnstoni) have plummeted by greater than 70% due to lethal ingestion of toxic invasive cane toads (Rhinella marina). Laboratory-based research has identified conditioned taste aversion (CTA) as a way to discourage consumption of toads. To translate those ideas into landscape-scale management, we deployed 2395 baits (toad carcasses with toxin removed and containing a nausea-inducing chemical) across four gorge systems in north-western Australia and monitored bait uptake with remote cameras. Crocodile abundance was quantified with surveys. Free-ranging crocodiles rapidly learned to avoid toad baits but continued to consume control (chicken) baits. Toad invasion at our sites was followed by high rates of crocodile mortality (especially for small individuals) at a control site but not at nearby treatment sites. In areas with high connectivity to other waterbodies, repeated baiting over successive years had continuing positive impacts on crocodile survival. In summary, we succeeded in buffering the often-catastrophic impact of invasive cane toads on apex predators.

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.

Imperfect adaptation by freshwater crocodiles to the invasion of a toxic prey species

Novel interactions between invaders and native species that have evolved in their absence may impose strong selective pressures that drive species to extinction or prompt rapid co-evolution and learning. Here, we report on the effects that invasive cane toads, a toxic prey species, have had on freshwater crocodile populations in 7 waterholes of the Victoria River, Australia, before and up to 14 years after toads invaded. We recorded observations of crocodiles attacking toads, dissected dead crocodiles to determine if they had eaten toads and indexed the abundances of cane toads, live crocodiles and dead crocodiles. Following toad-invasion we observed crocodiles attacking cane toads. Dead crocodiles were only observed following the invasion of toads and 62% of the 71 dead crocodiles we dissected had toads in their stomachs. Counts of dead crocodiles showed a humped relationship with time since toad invasion and declined markedly after 3 years post-toad invasion. Live crocodile abundance declined sharply following toad-invasion, but this decline attenuated approximately 4 years post-invasion. The pulse of crocodile mortality and attenuation of the rate of crocodile population decline suggests that crocodiles have evolved or learned to enable co-existence with toads. However, crocodile populations have shown no sign of recovery in the 8–14 years post toad invasion. Our findings highlight that adaptation by native species to the presence of invaders may be imperfect and thus may not necessarily entail numerical recovery of populations to pre-invasion levels, but instead downward shifts to new equilibria due to ongoing interactions with invaders.

Assessment of Nile crocodile utilization (<i>Crocodylus niloticus</i>) in Dunukofia Local Government Area, Anambra State, Nigeria

Assessment of Nile Crocodile utilization was carried out in six communities of Dunukofia local government area in Anambra state. A sampling intensity of 0.5% of the total population of each community was used to get a sample size of 323 respondents. Data were collected through questionnaire and complemented with personal observation and in-depth interview. The data collected were analyzed using descriptive statistics such as frequency, percentage and mean and presented as tables and charts. Results revealed that 85.14% of the respondents do not utilize crocodile meat as food while 14.86% of the respondents utilize crocodile meat as food. The highest number of respondents (66.67%) eat crocodile meat because of its taste while the least number (2.08%) because it is cheap. Results on non-consumptive utilization of Nile crocodile revealed that highest number of respondents (43.65%) utilize crocodile for traditional medicine while the least number (6.19%) reported that crocodile is utilized for tourism. The result also revealed that the sources of crocodile are the river (68.42%), markets (28.17%), and hunters (3.41%). A high percentage of the respondents (88.50%) are not interested in starting crocodile farming while 11.50% of the respondents are interested in starting crocodile farming. Majority of the respondents (65.73%) are not interested in starting crocodile farming because crocodiles are dangerous, 21.68% do not have the skills, 7.34% said crocodile farming is not popular and the least (5.24%) reported that it is high capital. Crocodile body parts utilized as revealed by the respondents were the whole body (53.56%), the head (30.03%), the limbs (10.84%), and the tail (5.57%). It is recommended that the locals be encouraged to engage in crocodile farming to help conserve the remaining crocodile population in the wild as well as create employment opportunities.

Distribution of Dwarf Crocodile (Osteolaemus Tetraspis Cope, 1861) Populations on the Outskirts of the Ebo Forest: Implications for Conservation

Purpose: The study was carried out in three riparian areas of the Ebo forest (Iboti, Lognanga and Ndokmem-North zones) to determine the distribution and status of dwarf crocodiles, and environmental factors influencing their distributions. 
 Materials and Methods: Survey on the various listed sites were carried out during the months of April, May and June 2023. The Qgis software was used to produce the distribution map of dwarf crocodiles in the periphery of the Ebo forest from the coordinates recorded at 11 water points using a GPS and 37 fishermen/ hunters were interview.
 Findings: The species were classified according to their status defined according to the IUCN red list protocol. The study showed that of the 11 water points studied, 6 were home to dwarf crocodiles, representing a proportion of 54.54%. Although we did not observed dwarf crocodiles in the watercourses in the Iboti zone, their presence is more established in the Lognanga zone (60%) than in the Ndokmem-north zone (40%). The average density of dwarf crocodiles in the periphery of the Ebo forest is around 0.50 crocodiles/km of riverbank covered. This implies that the population of dwarf crocodiles is decreasing and there is high need to increase conservation efforts to protect it from disappearing within the Ebo forest area.
 Implications to Theory, Practice and Policy: To guarantee the survival and viability of crocodiles in the periphery of the Ebo forest, it is necessary to opt for organic agriculture, monitoring the quality of rivers and water bodies and regular ecological monitoring of crocodiles.

An assessment of survey techniques using unmanned aerial vehicles to monitor Nile crocodiles (Crocodylus niloticus)

Monitored populations of the Nile crocodile Crocodylus niloticus at the southern end of its distribution, in the KwaZulu-Natal province of South Africa, are largely in decline. Trophy hunting of wild Nile crocodiles is only permitted at Pongolapoort Dam in the province, and monitoring of this population is required to enable the setting of annual hunting quotas. The aims of this study were to determine the feasibility of using drones to count and measure Nile crocodiles in the inlet to the dam and evaluate the utility of photomosaics, individual photographs, and videos for this purpose. A total of 16.5 km of shoreline was surveyed and 183 sub-adult and adult crocodiles observed, averaging 10.74 crocodiles per kilometer. The use of drones was cost-effective compared to traditional survey methods even though a higher number of person hours were required for data collection and processing. We recommend that drones be used to acquire video footage, supplemented by photomosaics in areas where large aggregations of crocodiles occur, to regularly monitor this crocodile population.

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.

Natal origin and dispersal of problem saltwater crocodiles in the Darwin Harbor, Australia

AbstractManagement programs that successfully recovered wild saltwater crocodile (Crocodylus porosus) populations in the Northern Territory of Australia did so with an expanding commitment to maintaining public safety. One aspect of the program is the ongoing removal of resident and immigrant crocodiles within Darwin Harbor (since 1979), the main urban center. We determined the likely sources of crocodiles caught as problem animals between 2015–2017 by comparing recently developed methods for population assignment. Depending on the assignment model used, we estimated that between 30% and 50% of crocodiles in Darwin Harbor originated from the Adelaide and Mary rivers, and the Kakadu region east of Darwin, and between 20% and 30% of crocodiles originated from the Finniss, Reynolds, and Daly rivers southwest of Darwin. Saltwater crocodiles occur at particularly high densities in these catchments. The remainder came from a mixture of different sources across the Northern Territory. The most common animals captured were immature (150–180 cm) males that have traveled 100–200 km. We did not identify any relationships between the distance from the inferred origin to Darwin Harbor and the size and sex of the crocodiles, or the year of capture. The targeted removal of crocodiles from specific sites such as Darwin Harbor, near where most people live, improves public safety in the highest risk areas, without compromising abundant source populations in most areas.

Preserving Pure Siamese Crocodile Populations: A Comprehensive Approach Using Multi-Genetic Tools.

Hybrids between the critically endangered Siamese crocodile (Crocodylus siamensis) and least-concern saltwater crocodile (C. porosus) in captive populations represent a serious challenge for conservation and reintroduction programs due to the impact of anthropogenic activities. A previous study used microsatellite and mitochondrial DNA data to establish the criteria for identifying species and their hybrids; however, the results may have been influenced by biased allelic frequencies and genetic drift within the examined population. To overcome these limitations and identify the true signals of selection, alternative DNA markers and a diverse set of populations should be employed. Therefore, this study used DArT sequencing to identify genome-wide single nucleotide polymorphisms (SNPs) in both species and confirm the genetic scenario of the parental species and their hybrids. A population of saltwater crocodiles from Australia was used to compare the distribution of species-diagnostic SNPs. Different analytical approaches were compared to diagnose the level of hybridization when an admixture was present, wherein three individuals had potential backcrossing. Approximately 17.00-26.00% of loci were conserved between the Siamese and saltwater crocodile genomes. Species-diagnostic SNP loci for Siamese and saltwater crocodiles were identified as 8051 loci and 1288 loci, respectively. To validate the species-diagnostic SNP loci, a PCR-based approach was used by selecting 20 SNP loci for PCR primer design, among which 3 loci were successfully able to differentiate the actual species and different hybridization levels. Mitochondrial and nuclear genetic information, including microsatellite genotyping and species-diagnostic DNA markers, were combined as a novel method that can compensate for the limitations of each method. This method enables conservation prioritization before release into the wild, thereby ensuring sustainable genetic integrity for long-term species survival through reintroduction and management programs.

Population dynamics of Morelet’s crocodile (Crocodylus moreletii) using data of national monitoring in Mexico

ABSTRACT Morelet’s crocodile populations have limited distribution along the coast of Mexico, Belize, and Guatemala, and have been greatly affected by human activities. Morelet’s crocodile is a species with high ecological and economic value. From an ecological perspective, it is an apex predator in the ecosystems in which it lives. Because of their vulnerable status is essential to have updated information on its populations over time to know their current conservation status. We analyze with a population model the vital rates of importance for the management and conservation of this species. Population growth with the Nocturnal Visual Detection model showed growth (λ = 1.027) over a 100 years, as in modeling Marking and Recapture of Specimens model (λ = 1.026). The largest reproductive value (v) was observed in the Adult stage (0.458). The sensitivity matrix indicated that the most sensitivity was offspring production by Adults (5.59). The data presented here show that the main factors impacting adult survival and the transition from Subadult to Adult stages alter population growth. Using the results of this model to quantitatively compare the conservation strategy can prove extremely useful to discern the parameters that must be taken into consideration and their potential effect on the population.

Trends of Attacks on Humans by Protected Crocodiles Along Rivers and Associated Habitats in Borneo Island

In the human-crocodile conflict, crocodile attacks on humans pose a serious threat and are becoming a complex conservation challenge in many countries. This study investigates the status and trend of crocodile attacks on humans in Malaysian Borneo (i.e., Sabah and Sarawak) where rivers and estuaries are inhabited by protected crocodile populations. Results show that between 2001 and 2020, a total of 205 attacks were reported which equals an average of nearly 11 cases per year. The number of attacks in Sarawak is estimated to be between 135 to 164 cases which is twice (p < 0.05) as high as in Sabah (70 cases), indicating a more serious human-crocodile conflict in the former. In Sabah, most of the attacks (81% or 57 cases) (p < 0.05) were in the districts of Lahad Datu, Kinabatangan, Tawau and Sandakan while in Sarawak (82% or 60 cases) (p < 0.05) were in Miri, Sri Aman, Kuching and Betong. Almost 80% (173 cases) of the victims were men between the ages of 30 and 39 who were fishing (42%) (p < 0.05) or bathing (27%) before the attack suggesting that such activities are risky and should be avoided in areas inhabited by crocodiles. Fatality rates of crocodile attacks have been increasing in recent years (i.e., 2015 - 2020) with an average of 10 cases per year. Therefore, control over the number of crocodile populations, especially the large-sized and dangerous individuals, needs to be implemented in high-risk areas. More research is needed to understand the capacity of their habitats to support optimal populations density and minimize conflicts with humans.

The state and perceptions of human-crocodile interactions around Murchison falls conservation area, Uganda

ABSTRACT Wildlife conflicts between people and large herbivores or mammalian carnivores are widely researched in Africa, but there is limited work on human-crocodile conflicts (HCC). In Uganda, conservation efforts have enabled the recovery of the Nile Crocodile (Crocodylus niloticus) population, yet the expanding human population and activities increasingly overlap with crocodile habitats resulting in negative interactions. This study used a combination of literature review, surveys, and the Nominal Group Technique to investigate the factors underpinning HCC around Murchison Falls Conservation Area. Results indicate that 115 attacks on humans occurred during 2012–2017, 84.3% of these being fatal. Also, 93.1% of the attacks occurred as victims were either fishing or collecting water. Construction of crocodile exclusion enclosures and translocation of problem crocodiles to protected areas were the most preferred mitigation measure. To reduce the prevalence of human injuries and offset local hostility toward crocodiles, conservation actors need to actively engage the affected communities.

Discovery of a suburban wetland refuge for a depleted American crocodile (Crocodylus acutus) population in northwestern Mexico, using a commercial Unmanned Aerial Vehicle

Background and Research Aims The Urías Coastal Lagoon (UCL) is a heavily modified and polluted lagoon near Mazatlán, in northwestern Mexico. Once abundant in the UCL, the American crocodile ( Crocodylus acutus) is now rarely seen in the area. A healthy population of apex predators is essential to maintain the trophic balance of ecosystems. Our research aim was to lay the groundwork for studies of American crocodile population ecology in the UCL. Methods Traditional boat surveys (day and night) of crocodiles were undertaken in the UCL in May-July 2022. Two exploratory aerial (∼ 30 m altitude) surveys of a small wetland located close to a habitational complex in the vicinity of the UCL were performed in June and December 2022, using a commercial Unmanned Aerial Vehicle (UAV). We used images obtained with the UAV to estimate the size of the crocodiles detected in the wetland. Results This study confirms the presence of American crocodiles in the UCL and presents the first information on individuals of this species for this area. Aerial surveys revealed the presence of 17 individuals in the wetland; the mean size of nine of those individuals was 183.3 ± 60 cm (range: 130-310 cm). Two yearlings (∼37 cm length), possibly born in June 2022, were captured in the same wetland in September 2022. We also surveyed 50.7 km of UCL coastline by boat, but no crocodiles were sighted. Conclusion The crocodiles seem to avoid the human-impacted UCL and likely use the less impacted surrounding wetlands as a refuge area, which they also use to reproduce. The presence of both yearlings and adults is a good sign for the survival of this vulnerable population. Implications for Conservation We believe that the surveyed wetland should be closely monitored for conservation purposes because it might be one of the last crocodile breeding refuges in the heavily modified and polluted coastal environment of the UCL. We summarize our results with a series of recommendations for local and federal authorities. These recommendations would likely help the conservation of the American crocodile population in the UCL.

Should the Identification Guidelines for Siamese Crocodiles Be Revised? Differing Post-Occipital Scute Scale Numbers Show Phenotypic Variation Does Not Result from Hybridization with Saltwater Crocodiles.

Populations of Siamese crocodiles (Crocodylus siamensis) have severely declined because of hunting and habitat fragmentation, necessitating a reintroduction plan involving commercial captive-bred populations. However, hybridization between Siamese and saltwater crocodiles (C. porosus) has occurred in captivity. Siamese crocodiles commonly have post-occipital scutes (P.O.) with 4-6 scales, but 2-6 P.O. scales were found in captives on Thai farms. Here, the genetic diversity and population structure of Siamese crocodiles with large P.O. variations and saltwater crocodiles were analyzed using mitochondrial DNA D-loop and microsatellite genotyping. Possible crocodile hybrids or phenotypic variations were ascertained by comparison with our previous library from the Siam Crocodile Bioresource Project. Siamese crocodiles with <4 P.O. scales in a row exhibit normal species-level phenotypic variation. This evidence encourages the revised description of Siamese crocodiles. Moreover, the STRUCTURE plot revealed large distinct gene pools, suggesting crocodiles in each farm were derived from distinct lineages. However, combining both genetic approaches provides evidence of introgression for several individual crocodiles, suggesting possible hybridization between Siamese and saltwater crocodiles. We proposed a schematic protocol with patterns observed in phenotypic and molecular data to screen hybrids. Identifying non-hybrid and hybrid individuals is important for long-term in situ/ex situ conservation.

Genetic diversity of a cichlid fish population after 100 years of isolation

AbstractHigh rates of species radiation have been recorded in Cichlids of East African lakes. The current study focused on a population of Nile tilapia (Oreochromis niloticus) found in a crater lake (Lake Crocodile) that occurs within the Central Island of Lake Turkana. The population separated from Lake Turkana about 100 years ago and has since then existed in isolation. This study aimed at assessing the existence of genetic differences between the Lake Crocodile Nile tilapia population and other closely related Nile tilapia populations from Lake Turkana, Lake Baringo and River Suguta. Genetic differences between the populations were evaluated using two mtDNA markers, and 16 microsatellite markers. Significant genetic differences (p &gt; 0.05) were observed between the Lake Crocodile population and the other studied populations within the region. Despite the shared ancestry between Lake Crocodile and Lake Turkana, genetic differences were observed between the two populations. This can mostly be attributed to the lack of gene flow and environmental differences between the two populations.

Conditional alternative movement tactics in male crocodiles

In species where conflict is costly, individuals adopt alternative movement tactics to minimise the risk of competitive interactions. Dominant males often maintain defined territories, while less competitive males may be forced to adopt alternative tactics to maximise fitness and reduce conflict. However, the extent to which males switch tactics according to current social or physiological status is poorly understood. Using implanted acoustic tags and a fixed array of tracking receivers, we investigated how the behaviour of 78 male estuarine crocodiles (Crocodylus porosus) shifted over an 11-year period in relation to ontogeny, body condition, and the extent of physical injuries. We discovered that male crocodiles sorted into three common movement classes, with 51% of males maintaining the same movement class across consecutive years (max = 9 years). Males > 4 m in total length maintained confined territories both within and across years and had the greatest extent of injuries and the highest condition score, indicative of territory holders. In contrast, smaller males sorted into high movement roamer or low movement site-philopatric tactics, where the tactic an individual adopted was less stable between years and did not correlate with condition or external injuries. Our study reveals the socio-biological mechanisms by which estuarine crocodiles coexist within a restricted habitat.Significance statementIdentifying individual-level differences in movement helps us predict which individuals are more likely to be involved in human-wildlife interactions. However, studying long-term shifts in movement is challenging, as large datasets of co-occurring individuals tracked in their natural environment over multiple years are required. We tracked a population of 78 male estuarine crocodiles (1030–4687 mm total length) in a shared environment over 11 years and assessed how eight movement traits were linked to body size and physical condition. At the population level, males sorted into different movement tactics according to ontogeny, with large territorial males having better body condition yet a greater incidence of injury. However, 49% of males showed variability across years, suggesting that tactics were conditional relative to environmental variability and a male’s own status. Our study provides insights into the mechanisms and costs of movement tactics in wild crocodile populations.

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.