Journal articles on the topic 'Dugongs'
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Cleguer, C., C. Garrigue, and H. Marsh. "Dugong (Dugong dugon) movements and habitat use in a coral reef lagoonal ecosystem." Endangered Species Research 43 (September 24, 2020): 167–81. http://dx.doi.org/10.3354/esr01061.
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Little is known about how the Vulnerable dugong Dugong dugon uses coral reef lagoons despite the importance of these habitats throughout much of its vast range. We used GPS satellite tracking systems to explore the space use of 12 dugongs at 3 locations in the coral reef lagoons of the main island of New Caledonia in the southwest Pacific: Cap Goulvain, Ouano and Nouméa. The movements of the tracked dugongs varied among individuals and all except one animal undertook large-scale movements (>15 km; mean [±SE] 37.7 ± 5.2 km) from their capture location (maximum waterway distance range: 13.8 to 72.9 km). The straight-line distances between the furthest GPS locations during each animal’s tracking period ranged from 21.3 to 74.5 km. We identified areas used intensively by dugongs in all 3 study areas, some of which were areas where seagrass presence has not been verified, or where dugongs have not been observed during past aerial surveys. Dugongs spent most of their tracking time within the lagoons, with 99.4% of GPS locations found inside the barrier reef. Nonetheless, where the lagoon was narrow and confined, 3 tracked dugongs used the fore reef shelf outside the barrier reef in the open ocean to commute between bays. Our findings can inform conservation and management initiatives in New Caledonia as well as other countries within the dugong’s range which have similar habitat geomorphology but where dugongs occur in numbers too low to be tracked and are considered Critically Endangered.
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Awadh, Asma, Maarifa Mwakumanya, and Mohamed Omar. "Dugongs' (Dugon Dugong) traditional values in Kenya; and their influence on their conservation." American Journal of Environment Studies 4, no. 2 (August 5, 2021): 1–13. http://dx.doi.org/10.47672/ajes.759.
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Purpose: This study aimed to assess Dugongs' status distribution of dugongs (Dugong dugon) in Kenya. A dugong is a herbivorous marine mammal of the tropical and subtropical Indo-West Pacific and the Indian Ocean. Dugongs are one of four existing species of the order Sirenia, which is considered most at risk of extinction. Globally, IUCN classified the Dugong as rare; Kenya has done the same under the Wildlife Conservation and Management Act 2013, thus making Dugongs a conservation priority. This paper discusses the traditional practices of dugongs and how this influenced their population and conservation.
Methodology: The study used a literature review, semi-structured questionnaires, guided interviews, and focus group discussions with respondents on obtaining data.
Findings: More than 100 dugongs occurred in the Kenyan waters in the 1960s; their population has declined drastically since then. Dugongs were a sought-after delicacy on the Kenyan coast. Dugong meat was consumed for its taste and nutritional use. In the northern study areas, its oil was separated and used for cosmetic and medicinal purposes.
Unique contribution to theory, practice and policy: This study confirms fishing practices and traditional consumption practices on dugongs were seen to have led to their detriment. The study recommends rich continuous education and awareness efforts to change the thinking and practices of the people towards conservation of dugongs and the environment in general.
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Awadh , Asma, Maarifa Mwakumanya, and Mohamed Omar. "Dugongs in Kenya – a survey on status and Trends." American Journal of Environment Studies 4, no. 1 (August 5, 2021): 76–87. http://dx.doi.org/10.47672/ajes.758.
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Purpose: The purpose of this study was to assess Dugongs' status distribution of dugongs (Dugong dugon) in Kenya. A dugong is a herbivorous marine mammal of the tropical and subtropical Indo-West Pacific and the Indian Ocean. Globally, IUCN classified the Dugong as rare; Kenya has done the same under the Wildlife Conservation and Management Act 2013, thus making Dugongs a conservation priority. The study's main objective was to assess dugongs' distribution and status for conservation in Kenya since the 1960s.
Methodology: The study employed a concurrent triangulation design to corroborate findings from three methods. The study used a literature review, semi-structured questionnaires, guided interviews, and focus group discussions with respondents on obtaining socio-economic data. Data was collected in fishing villages with documented and or anecdotal records of the availability of dugongs. Experiences 378 fishers were reached for the study. The study aggregated the number of dugongs sited by decades from the six sampled study sites and presented the data on a line graph. Further, the study computed the rate of change in dugongs from one decade to the next.
Findings: More than 100 dugongs occurred in the Kenyan waters in the 1960s; their population has declined considerably since then. The dugong habitat and feeding area have also shrunk over the same period, further aggravating the situation. There were more than thirty known dugong feeding areas in the study areas; only 10 of them are still known to host dugongs. An estimated 20 dugongs are known to be present in the Kenyan marine waters in the current times.
Unique contribution to theory, practice and policy: This study confirmed the presence of dugongs in Kenya. Further, the dugong numbers are very small, thus showing an urgent need for their conservation. Dugongs are found in Kiunga and Kisite Marine Protected Areas (MPAs) and their immediate surroundings; this amplifies the conservation value of the MPAs.
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SYAFUTRA, RANDI, WAHYU ADI, MUHAMMAD IQBAL, and INDRA YUSTIAN. "Short Communication: Dugong dugon Müller, 1776 (Sirenia, Dugongidae) in Bangka Island, Indonesia." Biodiversitas Journal of Biological Diversity 19, no. 3 (May 1, 2018): 823–30. http://dx.doi.org/10.13057/biodiv/d190310.
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Syafutra R, Adi W, Iqbal M, Yustian I. 2018. Short communication: Dugong dugon Müller, 1776 (Sirenia, Dugongidae) in Bangka Island, Indonesia. Biodiversitas 19: 823-830. Dugong dugon is a marine mammal species classified as Vulnerable. It has distribution in Indonesia, especially in Bangka Island. However, only four records of dugong were reported in Bangka Island in 1976, 2006, and 2007. In addition, there is little published information about local beliefs toward dugong and awareness actions toward dugong conservation in Bangka Island. This research compiled new records of dugong, local beliefs toward dugong, and awareness actions toward dugong conservation in Bangka Island. Sixteen new records of dugong were collected in Bangka Island leading to a total of 18 records for this island. All new records of dugong were obtained entirely from the eastern waters of Bangka Island. The new records also informed that most of the dugongs were found dead and entangled in gill nets. In addition, an interesting local belief caused Kurau Village becomes the most important location for fishermen to sell dead dugongs or dugongs’ meat. Furthermore, three main awareness actions toward dugong had been implemented in Bangka Island in 2017.
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Panyawai, Janmanee, and Anchana Prathep. "A Systematic Review of the Status, Knowledge, and Research Gaps of Dugong in Southeast Asia." Aquatic Mammals 48, no. 3 (May 15, 2022): 203–22. http://dx.doi.org/10.1578/am.48.3.2022.203.
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The dugong (Dugong dugon; Müller, 1776) is a vulnerable marine mammal species. This systematic review aims to provide information about the remaining populations, distributions, and habitat sites of the dugong in Southeast Asia. By combining this information with scientific research, critical knowledge gaps about dugongs in this region can be filled. This review showed that dugong populations have not only been reduced but also scattered in coastal waters. Little information is available about the remaining population numbers and distributions of dugongs. The largest estimated populations were reported around East Malaysia (688 to 1,376 dugongs); North Sulawesi, Indonesia (1,000 dugongs); and in the Andaman Sea, Thailand (200 to 250 dugongs). Published research has been very limited—approximately two articles per year. From 1993 until 2021, articles about the dugong were published in the context of ecology, conservation, biology, socioecology, biochemistry, and physiology. Visual and aerial surveying and anecdotal information about sightings and strandings of dugongs were the typical methods of research in Southeast Asia. The conservation strategy in this region is still focused on specific subject areas. The knowledge base for the species is lacking detailed quantitative data on remaining dugong populations, movements, habitats, and mating periods. Behavioral information lacks data for both spatial and temporal variations in foraging behavior, for example. Elucidation is needed in several different aspects of seagrass ecosystem dynamics. Improvements in captive dugong husbandry are also needed to ensure the sustainable conservation of the dugong in the region. National and international management decisions must be based on solid scientific data and multisector integration.
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Lanyon, JM, and H. Marsh. "Digesta Passage Times in the Dugong." Australian Journal of Zoology 43, no. 2 (1995): 119. http://dx.doi.org/10.1071/zo9950119.
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The retention times of particulate digesta were measured in two captive dugongs, Dugong dugon (Muller 1776) using inert plastic markers. The mouth-to-anus retention times (146-166 h) were similar to those of the West Indian manatee, and much longer than those of most other herbivorous mammals. This slow gut passage rate may be explained by the dugong's long digestive tract, the low fibre level of the diet and the low food intake. Like the manatee, the dugong appears to have a digestive strategy that is atypical of hindgut fermenters: low-fibre material is retained for extended periods within the long hindgut and almost completely digested.
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Tol, Samantha J., Rob G. Coles, and Bradley C. Congdon. "Dugong dugonfeeding in tropical Australian seagrass meadows: implications for conservation planning." PeerJ 4 (July 7, 2016): e2194. http://dx.doi.org/10.7717/peerj.2194.
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Dugongs (Dugong dugon) are listed as vulnerable to extinction due to rapid population reductions caused in part by loss of seagrass feeding meadows. Understanding dugong feeding behaviour in tropical Australia, where the majority of dugongs live, will assist conservation strategies. We examined whether feeding patterns in intertidal seagrass meadows in tropical north-eastern Australia were related to seagrass biomass, species composition and/or nitrogen content. The total biomass of each seagrass species removed by feeding dugongs was measured and compared to its relative availability. Nitrogen concentrations were also determined for each seagrass species present at the sites. Dugongs consumed seagrass species in proportion to their availability, with biomass being the primary determining factor. Species composition and/or nitrogen content influenced consumption to a lesser degree. Conservation plans focused on protecting high biomass intertidal seagrass meadows are likely to be most effective at ensuring the survival of dugong in tropical north-eastern Australia.
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Poommouang, Anocha, Promporn Piboon, Kittisak Buddhachat, Janine L. Brown, Wannapimol Kriangwanich, Siriwadee Chomdej, Jatupol Kampuansai, et al. "Microsatellite Polymorphism and the Population Structure of Dugongs (Dugong dugon) in Thailand." Animals 12, no. 3 (January 19, 2022): 235. http://dx.doi.org/10.3390/ani12030235.
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The dugong (Dugong dugon) is an endangered species of marine mammals, so knowledge of genetic diversity of these populations is important for conservation planning within different habitats. In this study, six microsatellite markers were used to assess the genetic diversity and population structure of 77 dugongs from skin samples of stranded animals collected from 1994–2019 (69 from Andaman Sea and 8 from the Gulf of Thailand). Our results found that dugongs in the Andaman Sea had higher genetic variation than those in the Gulf of Thailand. Populations in Trang, Satun, and some areas of Krabi had highest diversity compared to other regions of Thailand. Bayesian genetic clustering analysis revealed that dugongs in Thailand consist of five genetic groups. Moreover, dugongs in the middle and lower Andaman Sea presented the greatest gene flow compared to other regions. However, based on calculation of inbreeding coefficients (Fis value = 0.239), dugong populations in the Sea of Thailand are experiencing some levels of inbreeding, and so may warrant special protections. These results provide important information for understanding the genetic status of dugongs that can lead to improved management and conservation of this endangered species.
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Louise Chilvers, B., Steven Delean, Nicholas J. Gales, Dave K. Holley, Ivan R. Lawler, Helene Marsh, and Anthony R. Preen. "Diving behaviour of dugongs, Dugong dugon." Journal of Experimental Marine Biology and Ecology 304, no. 2 (June 2004): 203–24. http://dx.doi.org/10.1016/j.jembe.2003.12.010.
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KWAN, DONNA, HELENE MARSH, and STEVEN DELEAN. "Factors influencing the sustainability of customary dugong hunting by a remote indigenous community." Environmental Conservation 33, no. 2 (June 2006): 164–71. http://dx.doi.org/10.1017/s0376892906002992.
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The sustainability of indigenous customary hunting and fishing in remote areas can be influenced by human factors operating at global as well as regional and local scales because of the hybrid nature and sectoral interactions of the local economic environment. The internationally significant population of dugongs (Dugong dugon or seacow) in Torres Strait between Australia and Papua New Guinea supports an important indigenous fishery. The economic, socio-cultural and environmental factors that influenced hunting activity in 1998 and 1999 by the members of the community of Mabuiag Island were investigated to inform the sustainable management of the fishery. The landed catch during the eight months March to October of 145 dugongs in 1998 and 170 dugongs in 1999 potentially provided the community with an average of 290 g of dugong meat per person per day. Fifty-seven per cent of adult males on the island participated in dugong hunting, but more than half the catch in each year was caught by only two hunters. The probability of at least one person from the community going dugong hunting in 1998 and 1999 was 0.59 ± 0.02 per day. This probability was influenced by local environmental factors, including the abundance of dugongs in the traditional hunting grounds (affected by wind speed, year, season and lunar day) and the size of the commercial crayfish catch (which is influenced by the global market price, as well as local conditions). Although dugong hunting remains a very important part of the islanders’ contemporary culture and customary economy, the capacity to hunt dugongs is facilitated by the ease with which some hunters move between the state, commercial and customary sectors of their local economy. The complexities of the economic, social and cultural environments need to be considered in planning for the sustainable harvesting of threatened species by remote indigenous communities.
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N. Maitland, R., I. R. Lawler, and J. K. Sheppard. "Assessing the risk of boat strike on Dugongs Dugong dugon at Burrum Heads, Queensland, Australia." Pacific Conservation Biology 12, no. 4 (2006): 321. http://dx.doi.org/10.1071/pc060321.
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The risk of mortality due to boat strike is increasingly being recognized as an important management issue for marine wildlife, including Dugongs Dugong dugon. Ameliorating the effects of boat strike requires assessment of how that risk varies over the management area. This is dependent on the distribution and movements of both Dugongs and boats and on the physical characteristics of the area, particularly depth. In this study we assess these features for a small community that is dependent on tourism centred around recreational fishing and which is home to a regionally significant Dugong population. During one of the most popular holiday times, boats accessing the favoured fishing site pass directly through the core area of Dugong activity. Our data show that boat strike risk to Dugongs can be lowered significantly with minimal imposition on boaters. Boaters can avoid the area of highest risk by travelling around it in deeper water. However, this straightforward solution is only possible because of the restricted spatial scale of Dugong activity and the proximity of a deepwater channel enabling boaters to easily avoid shallow areas where boat strike risk is highest.
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Kiszka, Jeremy J. "Atypical associations between dugongs (Dugong dugon) and dolphins in a tropical lagoon." Journal of the Marine Biological Association of the United Kingdom 87, no. 1 (February 2007): 101–4. http://dx.doi.org/10.1017/s0025315407055129.
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Several types of relationships link organisms to each other, including competition, predation and various types of associations. This paper presents the first case of association/interaction between dugongs, Dugong dugon, the only strictly marine herbivorous mammal, and three species of tropical dolphins in and around the lagoon of Mayotte (45°10'E 12°50'S), in the western tropical Indian ocean. Data were collected opportunistically from 1999 to 2005 in the surrounding waters of Mayotte from boat (N=2 observations) and ULM (ultra-light motorized vessel, N=2). The dolphin species involved in associations with dugongs were Indo-Pacific bottlenose dolphin, Tursips aduncus, Indo-Pacific humpback dolphin, Sousa chinensis, and spinner dolphin, Stenella longirostris. In one case, dugongs were associated with both bottlenose and humpback dolphins. Associations were observed in the protected waters of the lagoon and outside, along the external slope of the barrier reef. Group size, activity and group structure of each species were recorded. Behavioural observations suggest that dugongs and dolphins were engaged in similar activities, such as travelling, on several occasions and were clearly associated when group formation was tight. If dolphins and dugongs may not associate for feeding purposes, then these interactions may occur: (1) for predation avoidance toward sharks; or (2) without any ecological reasons due to dolphin and dugong habitat overlap around the island.
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Pyenson, Nicholas D., Mehsin Al-Ansi, Clare M. Fieseler, Khalid Hassan Al Jaber, Katherine D. Klim, Jacques LeBlanc, Ahmad Mujthaba Dheen Mohamed, Ismail Al-Shaikh, and Christopher D. Marshall. "Fossil Sirenia from the Pleistocene of Qatar: new questions about the antiquity of sea cows in the Gulf Region." PeerJ 10 (October 18, 2022): e14075. http://dx.doi.org/10.7717/peerj.14075.
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One of the largest and least documented populations of dugongs (Dugong dugon) resides in the coastal waters of the United Arab Emirates, and waters surrounding Saudi Arabia, Bahrain, and Qatar. The archaeological record of dugongs in the Gulf Region is abundant, but little is known about their fossil record in the region. Here we report an isolated sirenian rib fragment from the Futaisi Member of the Fuwayrit Formation near the town of Al Ruwais, in northern Qatar. The Fuwayrit Formation is a marine Pleistocene deposit exposed onshore in Qatar and the United Arab Emirates. Based on the correlative dating of the basal Futaisi Member with other onshore platforms, the rib fragment is approximately 125 ka. We propose that this isolated rib (likely the first rib from the right side) belongs to Dugongidae, with strong similarities to extant Dugong. We cannot, however, eliminate the possibility that it belongs to an extinct taxon, especially given its similarities with other fossil dugongid material from both Qatar and elsewhere in the world. Aside from reflecting the presence of Gulf seagrass communities in the Pleistocene, this occurrence also suggests that different (and potentially multiple) lineages of sirenians inhabited the Gulf Region in the geologic past.
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Wirsing, Aaron J., and Michael R. Heithaus. "Behavioural transition probabilities in dugongs change with habitat and predator presence: implications for sirenian conservation." Marine and Freshwater Research 63, no. 11 (2012): 1069. http://dx.doi.org/10.1071/mf12074.
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Although not widely appreciated, prey can manage predation risk by modifying the sequence of their behavioural states. We explored this phenomenon in dugongs (Dugong dugon) subject to spatially and temporally variable risk of tiger shark (Galeocerdo cuvier) predation in Shark Bay, Australia. Dugong behaviour was assayed using focal follows and organised into sequences of foraging, resting, and travelling bouts. We used log-linear analysis to test for sequence differences in relation to habitat (deep, shallow) and predation danger (sharks present, largely absent). Dugongs modified their behavioural sequences between periods of high and low shark abundance: those at risk alternated more frequently between foraging, which constrains anti-predator vigilance, and travelling, which facilitates predator detection. Dugongs also avoided continuous series of resting bouts, during which awareness is reduced, when sharks were present. These changes were only observed in relatively dangerous shallow habitat, which is hunted disproportionately by tiger sharks; behavioural responses to sharks in deep habitat were modest. We conclude that dugongs in risky habitat resort to safer behavioural sequences in response to sharks. Given that human disturbance and predators are perceived similarly by many species, some forms of vessel interaction could compromise the fitness of sirenians by eliciting similar behavioural adjustment.
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André, Jessica, Emma Gyuris, and Ivan R. Lawler. "Comparison of the diets of sympatric dugongs and green turtles on the Orman Reefs, Torres Strait, Australia." Wildlife Research 32, no. 1 (2005): 53. http://dx.doi.org/10.1071/wr04015.
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This study investigated the diet of dugongs (Dugong dugon, Dugongidae) and green turtles (Chelonia mydas, Cheloniidae) on the Orman Reefs in Torres Strait, between Australia and Papua New Guinea, where large numbers of these animals live sympatrically. The stomach contents of dugongs and green turtles caught in an indigenous fishery were examined. Dugongs fed exclusively on seagrasses (mainly Thalassia hemprichii, Cymodocea spp. and Syringodium isoetifolium) whereas turtles consumed both seagrasses (especially T. hemprichii and Enhalus acoroides) and algae (mainly Hypnea spp., Laurencia spp. and Caulerpa spp.). The two herbivores showed no overlap in resource use except for the seagrass T. hemprichii, which was abundant in the feeding area. Both species appeared to feed selectively and did not just consume the most available food items. These results are suggestive of partitioning of food resources between dugongs and green turtles but a full explanation requires more detailed, and concurrent, study of the food resources and the animals’ movements.
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Cherdsukjai, Phaothep, Kittisak Buddhachat, Janine Brown, Manthanee Kaewkool, Anocha Poommouang, Patcharaporn Kaewmong, Kongkiat Kittiwattanawong, and Korakot Nganvongpanit. "Age relationships with telomere length, body weight and body length in wild dugong (Dugong dugon)." PeerJ 8 (November 11, 2020): e10319. http://dx.doi.org/10.7717/peerj.10319.
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The ability to estimate age and determine the growth status of free-ranging dugongs (Dugong dugon) is vital to providing insight into the basic biology of this endangered species. Currently, age estimation in dugong carcasses relies on counting dentin growth layer groups (GLGs) in tusks, but a disadvantage is they need to be intact. We explored whether measures of telomere length could be used as an alternative approach to age estimation in dugongs given that in other species, telomere length and age are inversely related. In this study, relative telomere length (rTL) was measured by qPCR in skin samples from 24 dugongs of varying ages determined by counts of GLGs. In addition, relationships between age by GLG counts and body weight and length and were examined. Our findings indicate that age estimated by GLGs was negatively correlated with telomere length using the logistic formula with a rate of telomere attrition of approximately 0.036 rTL/year between the ages of 5–20 years. By comparison, both body weight and length were positively correlated with GLG-based age, with growth rates of ~8.8 kg/year for weight and ~3.58 cm/year for length, respectively. After that, growth rates slowed substantially and then plateaued. The results suggest that physical maturity in dugongs occurs at 20 years of age and that measures of rTL might serve as a tool for age estimation in dugongs, living and deceased.
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Rajamani, Leela. "Using community knowledge in data-deficient regions: conserving the Vulnerable dugong Dugong dugon in the Sulu Sea, Malaysia." Oryx 47, no. 2 (April 2013): 173–76. http://dx.doi.org/10.1017/s0030605312000154.
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AbstractCommunity knowledge of the status, threats and conservation issues affecting the dugong Dugong dugon was investigated in the Sulu Sea, Malaysia. Interviews with local fishermen were conducted in 12 villages from the tip of Tanjung Inaruntung to Jambongan Island, in northern Sabah, Malaysia. According to the respondents dugong numbers are low and sightings are rare. Dugongs have been sighted around Jambongan, Tigabu, Mandidarah and Malawali Islands. The apparent decline of the dugong in this area is possibly because of incidental entanglement in nets, and opportunistic hunting. Seagrasses are present and have economic importance to the community. The fishermen have difficulty in understanding issues of conservation in relation to dugongs. I recommend that conservation initiatives begin with dialogue and an education programme, followed by incentives for development of alternative livelihoods. Using community knowledge for conservation purposes may be the only option in data-deficient regions, especially where financial constraints are high and the need for management intervention for threatened species is urgent.
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Lee, Paige Biqi, and Vincent Nijman. "Trade in dugong parts in Southern Bali." Journal of the Marine Biological Association of the United Kingdom 95, no. 8 (September 7, 2015): 1717–21. http://dx.doi.org/10.1017/s0025315415001423.
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Dugong Dugong dugon Lacépède, 1799, a globally threatened marine mammal that occurs in the coastal waters of the Indian and Pacific Ocean, is traded in small numbers throughout their range. We surveyed 128 shops selling wildlife in seven (June 2013) and eight (July 2014) towns on the island of Bali, one of Indonesia's most popular tourist destinations. Dugongs are protected under Indonesian law and CITES Appendix I Iisting precludes international trade. Despite this dugong parts were observed in trade in Denpasar, Mengwi and Sanur where 14 traders were interviewed. We recorded over 130 dugong parts, including raw bones and teeth but also many carved items and some derivatives, with no noticeable difference between years. The most common items were cigarette pipes carved from, predominantly, dugong ribs, and decorative carvings from bone and teeth. The total value of the items observed was $1500–3000. The trade was open and qualitatively similar to trade in parts of non-protected species. Information from traders suggests that dugongs are caught throughout Indonesia, and are both targeted specifically and caught accidentally. It is imperative for the management of dugongs to take the illegal trade in dugong parts into account and for the authorities to curb the trade by taking appropriate action in line with Indonesia's legislation. Greater awareness of the plight of the dugong, including the impediments to their conservation posed by the illegal trade in body parts, by the residents of and visitors to Bali, may aid in pressuring the authorities to take these steps.
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Gole, Swapnali, Sumit Prajapati, Nehru Prabakaran, Jeyaraj Antony Johnson, and Kuppusamy Sivakumar. "Herd Size Dynamics and Observations on the Natural History of Dugongs (Dugong dugon) in the Andaman Islands, India." Aquatic Mammals 49, no. 1 (January 15, 2023): 53–61. http://dx.doi.org/10.1578/am.49.1.2023.53.
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In the last four decades, dugong (Dugong dugon) aggregations have been rarely reported from the geographically isolated, vast seascape of the Andaman Islands, India. The Indian Ocean tsunami of 2004, hunting, coastal development, and habitat loss are the major causes of this change in the social system of dugongs in the Andaman Islands. Our long-term monitoring study (2017 to 2022) reveals a changing trend in aggregating behaviour of dugongs. In an inclusive, collaborative effort, we engaged multiple stakeholders using two approaches: (1) creating a spatially spread citizen science network targeting sea-faring agencies—the fishers, forest department, SCUBA divers, and defence bodies (Indian Navy and Indian Coast Guard); and (2) conducting standardized questionnaire surveys (UNEP/CMS) with fishers. Our approach yielded reports of 63 herd sightings of dugongs from the Andaman archipelago. The fishers reported 73.01% of the sightings, followed by the defence bodies (20.63%), forest department (3.18%), and SCUBA divers (3.18%). Smaller herds in our study comprised three to six individuals, with a social structure of “adults only” and “adult–calf.” The larger herds of seven to 13 individuals included an “adult–calf” combination with a greater number of adults accompanying two to three calves. More than 95% of these herd occurrences were reported from sheltered, coastal waters with resource concentrations (large seagrass meadows). Further, we present novel dugong occurrence reports from data-deficient regions like the Jarawa Tribal Reserve and the North Sentinel Island, along with dugong occurrences from Little Andaman, where the population was speculated to be locally extinct after the 2004 tsunami. These findings strongly advocate the involvement of multiple stakeholders as a cost-effective approach to monitoring the distribution and population of dugongs in larger seascapes like the Andaman and Nicobar Islands. Moreover, such an approach would be critical for sensitizing the local stakeholders regarding the conservation and management of large marine mammals such as dugongs.
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Amany, C., M. M. Kamal, F. Kurniawan, and V. Sabila. "Seagrass, dugong, and people: Lessons learned from community-based conservation in Tolitoli Regency, Sulawesi Tengah, Indonesia." IOP Conference Series: Earth and Environmental Science 967, no. 1 (January 1, 2022): 012032. http://dx.doi.org/10.1088/1755-1315/967/1/012032.
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Abstract Dugong (Dugong dugon) is a protected mammal in Indonesia. Hunting for dugongs is still very high, so that the status of this animal is threatened, one of which is in Tolitoli Regency, Central Sulawesi. Hence, conservation efforts need to be carried out, both species and habitat area. Based on observation and interviews, dugong conservation in Tolitoli Regency was community-based habitat management. Kelompok Masyarakat Pengawas or Monitoring Community Group (Pokmaswas) was a form of community-based management in charge of maintaining, protecting, and preserving the existence of dugong and seagrass protection. From a community perspective, significant indicators in the management of dugong habitats were community awareness, seagrass percentage, and management quality. There was 11 kind of seagrass species have been identified in Tolitoli Regency. Seagrass conditions in all three villages were characterized by less than 60% of seagrass cover, especially seagrass that was close to the shoreline. The appearance of dugongs is based not only on good seagrass conditions but also on sea conditions and ship traffic.
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Marsh, H., RIT Prince, WK Saafeld, and R. Shepherd. "The distribution and abundance of the dugong in Shark Bay, Western Australia." Wildlife Research 21, no. 2 (1994): 149. http://dx.doi.org/10.1071/wr9940149.
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In July 1989, dugongs were counted from the air at an overall sampling intensity of 7.9% over 14 239 km2 in Shark Bay, Western Australia. Counts were corrected for perception bias (the proportion of dugongs visible in the transect that are missed by observers), and standardised for availability bias (the proportion of animals invisible because of water turbidity) with survey-specific correction factors. The resultant minimum population estimate was 10146 � 1665 (s.e.) dugongs at an overall density of 0.71 � 0.12 (s.e.) dugongs km-2, the highest density ever recorded on a large-scale dugong survey. The proportion of calves (19%) was higher than for most other dugong surveys conducted in Shark Bay and elsewhere, suggesting an exceptionally high calving rate in 1988. Dugong density was highest (>5 km-2) in relatively deep water (12-16 m) in the eastern half of Shark Bay opposite the tip of Peron Peninsula and in the western Bay opposite the northern half of Dirk Hartog Island. Fewer than 4% of dugongs sighted in Shark Bay during the survey were in waters colder than 18�C. Results of aerial surveys over 906 km2 in the Faure Sill region of the eastern Bay in November 1990 and January 1991 suggest that between a third and a half of the dugongs in Shark Bay are located in this region during the summer. In contrast, only one dugong was sighted there during the winter survey. The survey confirms that Shark Bay is an internationally significant dugong habitat.
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Preen, Anthony. "OBSERVATIONS OF MATING BEHAVIOR IN DUGONGS (DUGONG DUGON)." Marine Mammal Science 5, no. 4 (October 1989): 382–87. http://dx.doi.org/10.1111/j.1748-7692.1989.tb00350.x.
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Woolford, Lucy, Arthur Wong, Helen L. Sneath, Trevor Long, Susan P. Boyd, and Janet M. Lanyon. "Hematology of dugongs (Dugong dugon) in southern Queensland." Veterinary Clinical Pathology 44, no. 4 (November 27, 2015): 530–41. http://dx.doi.org/10.1111/vcp.12305.
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Whiting, SD. "Rocky Reefs Provide Foraging Habitat For Dugongs In The Darwin Region Of Northern Australia." Australian Mammalogy 24, no. 1 (2002): 147. http://dx.doi.org/10.1071/am02147.
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DUGONGS (Dugong dugon) are large mammalian herbivores found in tropical and sub-tropical waters from the east coast of Africa to Vanuatu in the western Pacific Ocean (Rice 1998). Foraging studies throughout their range indicate that their diet is dominated by seagrass (Marsh et al. 1982; Preen 1995; Preen and Marsh 1995; Anderson 1998; Das and Dey 1999). Aerial surveys (Marsh and Saalfeld, 1989; Preen et al. 1997), land-based and boat-based observations (Anderson 1982 1994; Aragones 1994) and satellite tracking data (Marsh and Rathbun 1990) indicate that dugong distribution is closely associated with seagrass beds. Algae is known to occur in food samples from dugongs (Heinsohn and Birch 1972; Marsh et al. 1982; Erftemeijer 1994; Preen 1995) but its presence in the diet has been described as incidental (Marsh et al. 1982) or linked to large-scale losses of seagrass (Spain and Heinsohn 1973; Marsh et al. 1982; Preen and Marsh 1995). This note contains opportunistic observations of long-term feeding by D. dugon on algal covered rocky reefs in the Darwin region of the Northern Territory.
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Ponnampalam, Louisa S., J. H. Fairul Izmal, Kanjana Adulyanukosol, Jillian L. S. Ooi, and John E. Reynolds. "Aligning conservation and research priorities for proactive species and habitat management: the case of dugongsDugong dugonin Johor, Malaysia." Oryx 49, no. 4 (July 8, 2014): 743–49. http://dx.doi.org/10.1017/s0030605313001580.
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AbstractConservation efforts use scientific data to provide an adaptive framework wherein habitat and wildlife sustainability can co-exist with human activities. Good science informs decision-makers and facilitates the development of successful conservation approaches. However, conservation concerns for the dugongDugong dugonin South-east Asia are sufficiently urgent that action must be taken quickly, even though science has not provided complete answers to critical questions. In Johor, Malaysia, aerial surveys were conducted to assess dugong numbers, dugong high-use areas and overlap of dugong sightings with areas of seagrass. Dugong distribution included existing marine parks and locations where known conservation threats exist. We conclude that the Johor islands may represent a significant congregation site for dugongs in Peninsular Malaysia, with as many as 20 dugongs recorded in a single day. The existence of a marine park where the dugong sightings were most prominent is encouraging but only 38% of those sightings fell within the boundaries of the park. Anthropogenic threats need to be assessed and addressed prior to complex development activities such as dredging and coastal reclamation for tourism development in this critical area. We use this case to explore the concept of advancing species conservation through focused research and management, particularly where uncertainties exist because data are scarce.
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Lanyon, Janet M., Trevor Johns, and Helen L. Sneath. "Year-round presence of dugongs in Pumicestone Passage, south-east Queensland, examined in relation to water temperature and seagrass distribution." Wildlife Research 32, no. 4 (2005): 361. http://dx.doi.org/10.1071/wr04063.
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Pumicestone Passage is a narrow waterway that lies to the north of and adjacent to Moreton Bay, and between mainland Queensland and Bribie Island, Australia. Anecdotal reports have suggested that the Passage is home to dugongs year-round despite winter water temperatures that are known to cause dugongs to migrate elsewhere. To examine the pattern of distribution and abundance of dugongs within the passage on a year-round basis, eight years of sightings data collected by a charter boat operator were examined. Dedicated aerial surveys of the passage were also conducted at two-monthly intervals over two years, and more intensively over a single winter. Dugong sightings were examined in relation to water temperatures and seagrass prevalence. The number of dugongs sighted in the area on any one survey varied from 0 to 13. Dugongs were seen in all months of the year and in each of the eight winters, indicating that Pumicestone Passage is used year-round despite winter water temperatures dropping to below 18°C from June to August inclusive and below 16°C in June. All dugong sightings occurred in the southern part of the passage, south of Tripcony Bight. Dugongs were associated with shallows that support Halophila and Halodule species of seagrass, food species that are favoured elsewhere in their range. The northern part of the passage also supports seagrasses that are eaten by dugongs and has water temperature ranges that are not appreciably different to those of the southern passage. However, the narrow channels and very shallow nature of the northern passage provides little to no deep-water refugia for dugongs and the seagrass beds are less extensive. This study suggests that southern Pumicestone Passage requires protection concomitant with it being a year-round refuge of the vulnerable dugong.
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Yamato, Chiaki, Kotaro Ichikawa, Nobuaki Arai, Kotaro Tanaka, Takahiro Nishiyama, and Kongkiat Kittiwattanawong. "Deep neural networks based automated extraction of dugong feeding trails from UAV images in the intertidal seagrass beds." PLOS ONE 16, no. 8 (August 13, 2021): e0255586. http://dx.doi.org/10.1371/journal.pone.0255586.
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Dugongs (Dugong dugon) are seagrass specialists distributed in shallow coastal waters in tropical and subtropical seas. The area and distribution of the dugongs’ feeding trails, which are unvegetated winding tracks left after feeding, have been used as an indicator of their feeding ground utilization. However, current ground-based measurements of these trails require a large amount of time and effort. Here, we developed effective methods to observe the dugongs’ feeding trails using unmanned aerial vehicle (UAV) images (1) by extracting the dugong feeding trails using deep neural networks. Furthermore, we demonstrated two applications as follows; (2) extraction of the daily new feeding trails with deep neural networks and (3) estimation the direction of the feeding trails. We obtained aerial photographs from the intertidal seagrass bed at Talibong Island, Trang Province, Thailand. The F1 scores, which are a measure of binary classification model’s accuracy taking false positives and false negatives into account, for the method (1) were 89.5% and 87.7% for the images with ground sampling resolutions of 1 cm/pixel and 0.5 cm/pixel, respectively, while the F1 score for the method (2) was 61.9%. The F1 score for the method (1) was high enough to perform scientific studies on the dugong. However, the method (2) should be improved, and there remains a need for manual correction. The mean area of the extracted daily new feeding trails from September 12–27, 2019, was 187.8 m2 per day (n = 9). Total 63.9% of the feeding trails was estimated to have direction within a range of 112.5° and 157.5°. These proposed new methods will reduce the time and efforts required for future feeding trail observations and contribute to future assessments of the dugongs’ seagrass habitat use.
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Lanyon, Janet M. "Distribution and abundance of dugongs in Moreton Bay, Queensland, Australia." Wildlife Research 30, no. 4 (2003): 397. http://dx.doi.org/10.1071/wr98082.
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Dugong abundances in Moreton Bay (south-east Queensland) were estimated during six bi-monthly aerial surveys throughout 1995. Sampling intensity ranged between 20 and 80% for different sampling zones within the Bay, with a mean intensity of 40.5%. Population estimates for dugongs were corrected for perception bias (the proportion of animals visible in the transect that were missed by observers), and standardised for availability bias (the proportion of animals that were invisible due to water turbidity) with survey and species-specific correction factors. Population estimates for dugongs in Moreton Bay ranged from 503 ± 64 (s.e.) in July to 1019 ± 166 in January. The highest uncorrected count was 857 dugongs in December. This is greater than previous population estimates, suggesting that either previous surveys have underestimated abundance and/or that this population may have increased through recruitment, immigration, or a combination of both. The high degree of variation in population estimates between surveys may be due to temporal differences in distribution and herding behaviour. In winter, dugongs were found in smaller herds and were dispersed over a wider area than in summer. The Eastern Banks region of the bay supported 80–98% of the dugong population at any one time. Within this region, there were several dugong 'hot spots' that were visited repeatedly by large herds. These 'hot spots' contained seagrass communities that were dominated by species that dugongs prefer to eat. The waters of Rous Channel, South Passage and nearby oceanic waters are also frequently inhabited by dugongs in the winter months. Dugongs in other parts of Moreton Bay were at much lower densities than on the Eastern Banks.
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K. Bass, Deborah. "Status of Dugong Dugong dugon and Australian Snubfin Dolphin Orcaella heinsohni, in the Solomon Islands." Pacific Conservation Biology 16, no. 2 (2010): 133. http://dx.doi.org/10.1071/pc100133.
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Dugong Dugong dugon are listed as Vulnerable on the IUCN Red List and are thought to be in global decline. The species has become extirpated from many areas in its range in the Indo-Pacific, and the largest remaining population is believed to occur in the coastal waters of northern Australia and Melanesia. This study is the first survey done to assess the current status of dugongs in the Solomon Islands, an archipelago potentially providing extensive dugong habitat within the many coastal lagoons and seagrass meadows. In a region where traditional hunting of dugong is carried out, in addition to the increasing threats to its coastal habitat, the survival of the dugong is uncertain. Interview surveys were conducted to assess abundance, distribution, level of traditional hunting and mortality, and community attitude towards conservation of the species. The surveys provide a provisional insight into the dugong population and mortality in the Solomon Islands. The surveys also obtained sighting data for the Australian Snubfin Dolphin Orcaella heinsohni, a species endemic to Australia and Melanesia, but for which little occurrence information is available. The results indicate that dugong occur throughout the Solomon Islands, but rates of anthropogenic mortality are of concern, emphasising the potential value of protected areas and community engagement projects for the conservation of dugongs in this region.
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Aragones, LV. "Observations on dugongs at Calauit Island, Busuanga, Palawan, Phillipines." Wildlife Research 21, no. 6 (1994): 709. http://dx.doi.org/10.1071/wr9940709.
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A simultaneous monitoring system that used a team of local observers to count dugongs around Calauit Island, Busuanga, Palawan, Philippines, from eight vantage points was employed from March 1989 to May 1990 to identify important dugong habitats around the island. On average, five dugongs were seen per survey day. More dugongs were observed during March and July 1989 than in other months. These periods coincided with the bimodal peaking of seagrass biomass in the region and the lull between monsoons for that year. The site where dugongs were most often sighted was about 1.5 m deep, had the largest area of seagrass on the island (approximately 50 ha) and supported a seagrass (above-ground) biomass averaging 1060 g m-2 (wet weight). The dugongs were shy, making observations difficult. They were observed to graze at the study sites once per day, usually starting in the late afternoon or at night. Animals usually stayed on the seaward side of the spur-and-groove sections of the reefs. Short seagrasses such as Halophila ovalis, Halodule uninervis, Cymodocea rotundata, C. serrulata, Syringodium isoetifolium and Thalassia hemprichii showed more evidence of being grazed than the taller Enhalus acoroides. By direct observations of the area grazed by a single dugong, an average consumption rate of 30.5 kg (wet weight) of seagrass (above ground only) per day was estimated. The methodology developed in this study may be used to identify reserve areas for the protection of dugong habitats in the Philippines. The dugong populations of Palawan require further attention and implementation of conservation measures.
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Whiting, SD. "Dive times for foraging dugongs in the Northern Territory." Australian Mammalogy 23, no. 2 (2001): 167. http://dx.doi.org/10.1071/am01167.
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THERE are few published studies of dive times of dugongs (Dugong dugon). Direct observations are problematic because D. dugon are shy and difficult to observe in the wild from boats without creating observer effects. Time Depth Recorders (TDR?s) can record dive and surface times during dive behaviour, but there are no published data as yet for D. dugon using this technology. Although studies on dive times using Time Depth Recorders (TDR?s) result in larger data sets, their results are difficult to relate to particular behaviours such as foraging. This paper provides submergence and surface interval times for D. dugon obtained by direct observations in Darwin Harbour. Direct observations, although time consuming, can produce important information related to the ecology of D. dugon.
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Marsh, H., and DF Sinclair. "An Experimental Evaluation of Dugong and Sea Turtle Aerial Survey Techniques." Wildlife Research 16, no. 6 (1989): 639. http://dx.doi.org/10.1071/wr9890639.
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Some factors which affect the aerial counts of dugongs and sea turtles were examined experimentally. There was no significant difference in the observed density of dugongs when survey height was doubled from 137 m to 274 m with an accompanying doubling of transect width on either side of the aircraft from 200 m to 400 m. In contrast, a significantly higher density of turtles was observed at the lower heightharrower transect width. The higher level of glare on the exposed side of the aircraft, the time of day and the time from high tide made no significant difference to the observed densities of dugongs or turtles. The survey crew included a tandem team of two observers on each side of the aircraft, who reported their uncolluded observations into separate tracks of a two-track tape recording system. This allowed the reports of tandem observers to be compared in order to assess observer reliability. Overall, observers missed over 40% of dugong groups and over 80% of turtles visible within the transect including groups of more than 10 dugongs. The chance of observers missing a group of dugongs was independent of group size. There was little disagreement between tandem observers about the identification of animals, or the position of animals in the water column. However, observers differed markedly in their categorisation of dugong behaviour and in their counts of animals (particularly dugong calves) in larger groups.
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Anderson, PK. "Dugong distribution, the seagrass Halophila spinulosa, and thermal environment in winter indeeper waters of eastern Shark Bay, WA." Wildlife Research 21, no. 4 (1994): 381. http://dx.doi.org/10.1071/wr9940381.
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Five aerial survey transects in eastern Shark Bay, along which dugongs (Dugong dugon) had been reported in deep water in July 1989, were flown on 3 and 14 July 1992. As in 1989, dugong sightings were concentrated between 9- and 15-m depth contours. Thermal patterns shown on images obtained from NOAA satellites, and direct measurement of temperatures in the water column, confirmed that temperatures were at least 19�C where dugongs were concentrated. Although no seagrass had previously been reported in this zone, examination of benthic communities using a remotely controlled underwater video system revealed an apparently monospecific stand of Halophila spinulosa. Dugong behaviour, observed from a 10-m catamaran, indicated that the animals were diving to the bottom. Long, deep dives may be more costly in time and energy than the shorter dives characteristic of feeding in shallow water. H. spinulosa has large fleshy rhizomes similar to those known to contain abundant starch in other members of the genus and it is suggested that carbohydrate-rich rhizomes might compensate for the higher costs of foraging in deep water. Previously known stands of preferred forage species appeared inadequate to support the large dugong population of Shark Bay, but if temperatures are favourable throughout the winter and if the H. spinulosu observed in this study is available throughout the year, this H. spinulosa community may be an important resource for the Shark Bay dugong population.
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Bayliss, P., and WJ Freeland. "Seasonal Distribution and Abundance of Dugongs in the Western-Gulf-of-Carpentaria." Wildlife Research 16, no. 2 (1989): 141. http://dx.doi.org/10.1071/wr9890141.
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Aerial surveys of coastal waters (27 216 km2) in the western Gulf of Carpentaria during the dry season of 1984 and wet season of 1985 indicated no major seasonal changes in distribution and relative abundance of dugongs. Minimum population size in the dry season was estimated as 16 816 � 2946 (standard error), with a relative density of 0.62 k 0.11 km-2, and that for the wet season 16 846 + 3257, with a relative density of 0.62 � 0.12 km-2. The estimates exclude 5% of observations which could have been either dugongs or Irrawaddy dolphins, and were corrected for submerged dugongs and those missed on the surface. Dugongs were unevenly distributed over the study area, and neither mean group size nor proportion of calves varied between seasons. Dugong abundance was correlated with area of available seagrass. The catch rate of dugongs by Aboriginal people off Numbulwar decreased six-fold between the 1960s and 1985 (60 to 10 p.a.), possibly due to excessive hunting.
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Plaimo, P. E., I. L. Wabang, and A. Hendrizal. "Behavioral and Biophysical Studies of Dugong (Dugong dugon) Habitat in Waters Mali Beach, Kabola District, Indonesia." IOP Conference Series: Earth and Environmental Science 934, no. 1 (November 1, 2021): 012077. http://dx.doi.org/10.1088/1755-1315/934/1/012077.
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Abstract Dugongs are generally shy animals, so observing their existence is very limited to hundreds of meters. In contrast to the behavior of Dugong who lives in the coastal waters of Mali, Kabola Regency, Indonesia. Its uniqueness can interact with humans at a very close distance and can even be on the back. It is, therefore, necessary to explore other behavioral patterns and habits and biophysical habitats of Dugongs as information to maintain their survival. This research aims to find out the behavior and biophysics of dugong habitat in the coastal waters of Mali, Kabola Subdistrict, Indonesia. The study uses direct observation methods in the form of observing the characteristics and biophysical conditions of dugong habitats including (1) determining dugong activity areas using GPS coordinates; (2) observe habitat characteristics and biophysical conditions by observing biotic and abiotic conditions, and (3) measuring physicochemical parameters, namely temperature, salinity, and pH. Next, to observe the daily behavior of dugongs when interacting with their habitat environment in the form of time: breathing, going around the boat, swimming at the bottom, swimming on the surface, swimming in the water column, resting at the bottom, eating and exposing the back. In the observations, dugongs swimming around the ship immediately responded and then approached and rubbed his body to the leg then through the pectoral fins that tried to hug to get a leg on the model being tested. Then turn under the boat and remove the penis. In general, the biophysical conditions of sandy and dense habitats are overgrown with seagrass.
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Jamaludin, Abdul, Luthfiralda Sjahfirdi, and Riani Widiarti. "DUGONG (Dugong dugon) FEEDING BEHAVIOUR IN SEA WORLD INDONESIA, TAMAN IMPIAN JAYA ANCOL, JAKARTA." KnE Life Sciences 2, no. 1 (September 20, 2015): 504. http://dx.doi.org/10.18502/kls.v2i1.204.
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<p>Dugongs is a protected herbivorous marine mammals (Suwelo et al., 1992) and included in vulnerable category of IUCN(International Union for the Conservation of Nature and Natural Resources) and Appendix I CITES (Convention on International Trade in Endangered Species) (IUCN 2012). Dugong population continues to decline due to the human threat (Suwelo et al., 1992). Another factor is because Dugong has a low reproductive rate (Hindell & Kirkword 2003). Ex-situ conservation of dugong is become important and has conducted by Sea World Indonesia, Taman Impian Jaya Ancol, Jakarta. Research on dugong feeding behaviour can help the ex-situ conservation of dugong. This because feeding behaviour is a main daily behaviour of dugong in the sea (Chilvers et al., 2003). The aim of this research was to describe feeding behaviour of two dugong in Sea World Indonesia. Observations were made in SWI Dugong aquarium with a diameter of 10 meters and two different depth (2 meters and 5 meters). Observations were made during two weeks on December 2012. Behavioral observation time was divided into morning (9:15 to 09:35), (11:30 to 11:50) and <br />(14:30 to 14:50) observations. The feeding behavior observed was hand-fed, surface-fed and bottom-fed. Daily observations of dugong feeding behavior were done using focal animal sampling and ad libitum sampling. The data obtained was displayed in the form of tables and graphs. The data was analyzed using descriptive analysis reinforced with statistical tests. The statistical tests used were the t-test and ANOVA test. Hand-fed behavior of male dugong (31,30%) was higher than female (29,67%). Results from t-test showed that the hand-fed behaviors of both dugongs were not significantly different. Meanwhile, the other t-test result for surface-fed behavior and bottom-fed behavior of both dugongs was significantly different. Surface-fed behavior of male dugong (65.83%) was higher than female (32.08%). Bottom-fed behavior of male dugong (6.23%) was lower than females (36.63%). Hand-fed behaviour and feed on surface are the adaptation of feeding behavior in captivity. Feed on bottom behaviour is the behavior that similar to dugong feeding in the wild, which is grazing. Based on the observation, it is known that both dugong, male dugong especially, have a good adaptation on hand-fed seagrass behaviour and feed on surface, while the female dugong maintain its natural feeding behavior.</p><p><br /><strong>Keywords</strong>: Dugong dugon, Sea World Indonesia, feeding behaviour, captive</p>
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Whiting, Scott D. "Movements and distribution of dugongs (Dugong dugon) in a macro-tidal environment in northern Australia." Australian Journal of Zoology 56, no. 4 (2008): 215. http://dx.doi.org/10.1071/zo08033.
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A combination of aerial surveys, community sightings and satellite tracking revealed distribution, habitat, relative densities and spatial use of individual dugongs in the Darwin region of the Northern Territory. Aerial surveys in both the wet and dry seasons estimated relatively low densities of dugongs. Most group sightings (73% of all sightings) and densities up to 0.54 dugongs km−2 occurred in one of the four blocks surveyed. This block contained the Vernon Islands and large macro-tidal algal rocky reefs. Two dugongs tracked using satellite transmitters were captured above these reefs and kept a close association with similar reef types during most of their tracking periods of 53 and 154 days. Tracking revealed that dugongs used multiple and distinct areas for periods of several days to over 80 days and utilised coastal sections of up to 300 km in length. This indicates that dugong management in the Darwin region requires the consideration of large spatial scales, multiple habitat types and rocky reef habitat. Community sightings were an important information source and revealed locations of dugongs not identified with either the aerial surveys or satellite tracking.
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Gales, Nick, Robert D. McCauley, Janet Lanyon, and Dave Holley. "Change in abundance of dugongs in Shark Bay, Ningaloo and Exmouth Gulf, Western Australia: evidence for large-scale migration." Wildlife Research 31, no. 3 (2004): 283. http://dx.doi.org/10.1071/wr02073.
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The third in a series of five-yearly aerial surveys for dugongs in Shark Bay, Ningaloo Reef and Exmouth Gulf was conducted in July 1999. The first two surveys provided evidence of an apparently stable population of dugongs, with ~1000 animals in each of Exmouth Gulf and Ningaloo Reef, and 10 000 in Shark Bay. We report estimates of less than 200 for each of Exmouth Gulf and Ningaloo Reef and ~14 000 for Shark Bay. This is an apparent overall increase in the dugong population over this whole region, but with a distributional shift of animals to the south. The most plausible hypothesis to account for a large component of this apparent population shift is that animals in Exmouth Gulf and Ningaloo Reef moved to Shark Bay, most likely after Tropical Cyclone Vance impacted available dugong forage in the northern habitat. Bias associated with survey estimate methodology, and normal changes in population demographics may also have contributed to the change. The movement of large numbers of dugongs over the scale we suggest has important management implications. First, such habitat-driven shifts in regional abundance will need to be incorporated in assessing the effectiveness of marine protected areas that aim to protect dugongs and their habitat. Second, in circumstances where aerial surveys are used to estimate relative trends in abundance of dugongs, animal movements of the type we propose could lead to errors in interpretation.
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Satyaningtijas, Aryani Sismin, Agik Suprayogi, Huda Shalahudin Darusman, Ardiansyah Nurdin, and Desrayni Hanadhita. "Relative white blood cell counts, heterophil-to-lymphocyte ratio, and discovery of blood parasites in wild dugong (Dugong dugon) at Lingayan Island, Toli-toli, Indonesia." Veterinary World 13, no. 9 (2020): 1849–53. http://dx.doi.org/10.14202/vetworld.2020.1849-1853.
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Aim: This study was conducted to investigate the relative white blood cell (WBC) counts and the heterophil-to-lymphocyte (H/L) ratio and to analyze the presence of blood parasites in wild dugongs at Lingayan Island. It is expected that the results of this study could provide additional knowledge about the physiological conditions of wild dugongs in their natural habitats, which can serve as basic data in dugong conservation efforts, especially in Indonesia. Materials and Methods: A wild dugong was captured around Lingayan Island. Blood samples were collected from the saphenous vein, and blood smears were prepared immediately. The blood smears were examined for leukocyte identification, calculation of relative WBC counts, and presence of blood parasites. The H/L ratio was calculated based on the obtained relative WBC counts. Results: The relative WBC counts included heterophils 19.4%, lymphocytes 76.4%, and monocytes 3.6%, and the H/L ratio was 0.25. Intraerythrocytic parasites were identified and suspected to be Anaplasma and Babesia. Conclusion: This study reports leukocyte values from free-ranging dugongs captured in Lingayan Island, Indonesia. Based on the H/L ratio, the dugong examined, in this study, did not experience chronic stress. However, the discovery of blood parasites could be one of the threatening factors for the dugong population.
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Satyaningtijas, Aryani Sismin, Agik Suprayogi, Ardiansyah Nurdin, and Huda S. Darusman. "Physiological Value of Heart Rate, Respiration and Rectal Temperature of Wild-Captive Dugong (Dugong dugon)–A Case Study in Lingayan Island." HAYATI Journal of Biosciences 26, no. 4 (December 28, 2019): 147. http://dx.doi.org/10.4308/hjb.26.4.147.
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This study aims to obtain the physiological value of dugongs that live in natural habitats (in-situ) as protected wildlife, namely on the coast of Lingayan Island, Toli-Toli Regency. Wild dugongs caught on the beach were put into a net cage. After 14 days of living in a beach cage, measurements of heart rate, respiration, and body temperature were measured using non-invasive methods. This study showed that the value of heart rate, respiration, and body temperature were measured (80.00±17.32) beats/minutes, (17.33±6.80) inspiration/minute, and (32.75±0.07)°C. This physiological value is higher when compared to dugongs that live in captivity, this is likely due to the process of homeostasis through physiological adaptation mechanisms. The physiological value of the dugong is very important for the advancement of dugong animal health science and technology. Besides this finding can be a medical reference that is very useful for veterinarians in the diagnostic and therapeutic process.
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Meidina, T. S. A., M. M. Kamal, F. Kurniawan, H. S. Darusman, and A. A. Digdo. "Seagrass diversity and dugong observation in North Minahasa Regency, North Sulawesi." IOP Conference Series: Earth and Environmental Science 1137, no. 1 (January 1, 2023): 012054. http://dx.doi.org/10.1088/1755-1315/1137/1/012054.
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Abstract Dugong is a marine mammal that only eats seagrass. Feeding tracks of dugongs in the seagrass beds indicate their presence. The dugong population is currently experiencing a decline due to habitat destruction and other anthropogenic factors. This study aimed to determine the seagrass diversity and their relationship to the presence of dugongs. The research was conducted in villages of Bahoi, Tarabitan, Bulutui, and Gangga I Island using the seagrass-watch method. Analysis of the data used was the percentage of seagrass cover, density of seagrass species, and indicators of the presence of seagrass, which was carried out by interviewing fishermen and surveying their feeding tracks. The results showed that the waters in the North Minahasa Regency had seven seagrass types. The average percentage of seagrass cover was 61.73% and the density of seagrass species was 766.88 shoots/m2. Feeding tracks observed in three locations, in Bahoi, Tarabitan, and Bulutui villages. The most tracks of feeding tracks were in Bahoi Village, with the type of seagrass that dominated being eaten by dugongs was Halodule pinifolia. Based on the results obtained, it concluded that certain types of seagrass are related to the location of the emergence of dugongs in the North Minahasa Regency.
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Sheppard, James K., Anthony R. Preen, Helene Marsh, Ivan R. Lawler, Scott D. Whiting, and Rhondda E. Jones. "Movement heterogeneity of dugongs, Dugong dugon (Müller), over large spatial scales." Journal of Experimental Marine Biology and Ecology 334, no. 1 (June 2006): 64–83. http://dx.doi.org/10.1016/j.jembe.2006.01.011.
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Holley, David K., Ivan R. Lawler, and Nicholas J. Gales. "Summer survey of dugong distribution and abundance in Shark Bay reveals additional key habitat area." Wildlife Research 33, no. 3 (2006): 243. http://dx.doi.org/10.1071/wr05031.
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The first standardised summer aerial survey of dugongs within Shark Bay in Western Australia, and the fourth in a series of surveys of this area, was undertaken during February 2002. This survey returned a population estimate of 11 021 ± 1357 (s.e.), a result similar to the first two winter surveys in 1989 and 1994 but considerably lower than the 1999 survey. Distribution was markedly different in this survey compared with all previous surveys, which were conducted during winter, confirming that dugongs within Shark Bay undertake a seasonal migration driven by changes in sea surface temperature. In addition to this distribution pattern it was identified that 24% of the population during summer occurred within an area known as Henri Freycinet Harbour. That is, while dugongs have been reported in this south-western region of the bay previously in summer, this is the first time that the substantial size (2629 ± 780, s.e.) of the summer dugong population has been quantified. Differences in the population estimate between the 1999 survey and this survey may be explained through large-scale movement patterns of dugongs between Shark Bay and Ningaloo Reef and Exmouth Gulf to the north, patterns that should be considered in the management of dugongs for the entire region.
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McNiven, Ian J., and Ricky Feldman. "Ritually Orchestrated Seascapes: Hunting Magic and Dugong Bone Mounds in Torres Strait, NE Australia." Cambridge Archaeological Journal 13, no. 2 (October 2003): 169–94. http://dx.doi.org/10.1017/s0959774303000118.
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People dwell in a world of their own subjective making. For many hunters, engagement with the ‘natural’ world is a negotiated affair because animals, like people, possess spirits. A critical part of the negotiation process is mediation of the human–prey relationship by hunting magic. Torres Strait Islanders of NE Australia are skilled hunters of dugongs, a marine mammal whose capture entails a broad range of ritual practices. Following ethnographic expectations, excavation of bone mounds reveals ritual treatment of dugong bones, especially skulls, to increase hunting success. Extensive use of dugong bones in ritual sites has important implications for the extent to which ‘secular’ midden deposits are representative of Islander subsistence practices. Since dugong bone mounds provide archaeological insights into Islander spiritual relationships with dugongs, chronological changes in use of these sites inform us about historical developments in Islander ontology and their ritual orchestration of seascapes and spiritual connections to the sea.
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Bayliss, P. "Factors Affecting Aerial Surveys of Marine Fauna, and Their Relationship to a Census of Dugongs in the Coastal Waters of the Northern-Territory." Wildlife Research 13, no. 1 (1986): 27. http://dx.doi.org/10.1071/wr9860027.
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Some factors that may affect the aerial counts of dugongs, dolphins and turtles were examined experimentally. Tidal influence did not affect the counts of dugongs or dolphins, but those of turtles increased around high tide. A combined doubling of survey altitude and transect width reduced observed density of all three classes of animals by 50%. The counts of four observers did not differ significantly, but further data counsel caution. Overcast weather depressed counts of dugongs and turtles. Dolphin counts were affected by water surface condition, counts being lowest in choppy seas. A mark-recapture model was used on tandem observations to derive correction factors for groups of animals missed on the surface of a transect. Observers missed between 33% and 75% of dugong groups on the surface, the probability of detection decreasing with increased survey altitude and transect width. A similar range and pattern of probabilities was found for dolphins and turtles. Dugongs were censused in the coastal waters of the Northern Territory between the Daly River and Millingimbi in December 1983, an area of 28 746 km*2. Sampling intensity was 7.6%. A minimum population of 2953 � 530 (standard error) was estimated, an overall relative density of 0.11 � 0.02 km-2. A theoretical correction for submerged dugongs not seen yielded a total population estimate of 38 000, an overall density of 1.46 km-2. The distribution of dugongs in the survey area was patchy, the highest densities being associated with shallow coastal waters, sheltered bays, and large islands.
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Lanyon, Janet M., Keith Newgrain, and Teuku Sahir Syah Alli. "Estimation of Water Turnover Rate in Captive Dugongs (Dugong dugon)." Aquatic Mammals 32, no. 1 (January 1, 2006): 103–8. http://dx.doi.org/10.1578/am.32.1.2006.103.
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Lanyon, Janet M., Rob W. Slade, Helen L. Sneath, Damien Broderick, John M. Kirkwood, Duncan Limpus, Colin J. Limpus, and Tim Jessop. "A Method for Capturing Dugongs (Dugong dugon) in Open Water." Aquatic Mammals 32, no. 2 (June 1, 2006): 196–201. http://dx.doi.org/10.1578/am.32.2.2006.196.
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Cleguer, C., C. Garrigue, M. M. P. B. Fuentes, Y. Everingham, R. Hagihara, M. Hamann, C. Payri, and H. Marsh. "Drivers of change in the relative abundance of dugongs in New Caledonia." Wildlife Research 44, no. 4 (2017): 365. http://dx.doi.org/10.1071/wr16133.
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Context Sound understanding of temporal changes in the abundance of wildlife species is required for assessing their status and for effective conservation and management. In New Caledonia, a single baseline aerial survey of dugongs in 2003 estimated a population of 2026 (± 553 s.e.) individuals. A second, similar survey in 2008 produced a lower estimate of 606 (± 200 s.e.) individuals, leading to concerns that the dugong population was experiencing a decline. Aims This study used data collected from additional aerial surveys with the aim of updating information on the current size of the dugong population in New Caledonia and investigating the drivers of change in the estimates. Methods Four additional surveys were conducted: one in each of the cool (June) and warm (November) seasons of 2011 and 2012 around the main Island of New Caledonia. Dugong relative abundance and density were calculated and compared among survey years and survey regions. Drivers of change in the dugong population size were then investigated. Key results The abundance estimates obtained from our four surveys ranged from 649 (± 195 s.e.) to 1227 (± 296 s.e.) dugongs. These new results were not significantly different to the 2008 estimate but were significantly lower than the 2003 estimate. There was no significant variation in the proportion of calves throughout the entire time series of surveys. Conclusions The dugong population of New Caledonia was relatively stable between 2008 and 2012. We could not find sufficient evidence to show whether the discrepancy between 2003 and the remainder of the time series is due to a real decline in the population or the result of the confounding effects of variation in environmental conditions, animal behaviour and sampling biases. Implications The stability of the dugong population between 2008 and 2012 is a positive outcome for local conservation and management of dugongs. This study also highlights the advisability of replicating baseline surveys to enable robust interpretation of temporal variation in population size estimates, and in turn, to improve the management of wildlife species.
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Eigeland, Karen. "Bacterial Community Structure in the Hindgut of Wild and Captive Dugongs (Dugong dugon)." Aquatic Mammals 38, no. 4 (December 1, 2012): 402–11. http://dx.doi.org/10.1578/am.38.4.2012.402.
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Lanyon, Janet M., Helen L. Sneath, and Trevor Long. "Evaluation of Exertion and Capture Stress in Serum of Wild Dugongs (Dugong dugon)." Journal of Zoo and Wildlife Medicine 43, no. 1 (March 2012): 20–32. http://dx.doi.org/10.1638/2010-0178.1.
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