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  • 1
    In: Wildlife Research, CSIRO Publishing, Vol. 50, No. 4 ( 2022-11-4), p. 283-291
    Abstract: Context Unsustainable harvesting can threaten wildlife populations and jeopardise the livelihoods of people relying on wildlife resources. Although millions of rainbow mudsnakes (Enhydris enhydris) are harvested from wetland agroecosystems in tropical Asia each year, few detailed studies have been conducted on the biology of this species. Aims We aimed to address this knowledge gap by examining the reproductive biology and resilience to harvesting of E. enhydris, collecting from agricultural landscapes in West Java, Indonesia. Methods We measured and examined 1731 specimens that had been collected and killed for skins and meat near the city of Cirebon in West Java. Key results Most snakes that we examined were adults (94% of females, 88% of males), with females outnumbering males overall (69% female). Sex ratios varied seasonally and among processing facilities. Females attained larger body sizes than males, were more heavy-bodied, and had shorter tails relative to snout–vent length. Reproductive traits varied among months, with two peaks in the incidence of gravid snakes occurring in March and September. Litter sizes averaged 11.2 (range 2–31) and increased with maternal body size. About half of the adult females were reproductive (vitellogenic or gravid) at the time of collection. This proportion increased with maternal body size, such that 60–70% of large females were reproductive at the time of collection, suggesting that some females may produce two litters per year. Conclusions Rainbow mudsnakes remain exceptionally abundant in West Java, despite significant habitat modification and intensive harvesting. Implications The ability of this species to exploit anthropogenic subsidies in disturbed agricultural landscapes gives it access to plentiful food, and the resultant early maturation, frequent reproduction, and high fecundity enable it to withstand high levels of commercial offtake.
    Type of Medium: Online Resource
    ISSN: 1035-3712 , 1448-5494
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2022
    SSG: 12
    SSG: 23
    Location Call Number Limitation Availability
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  • 2
    In: Wildlife Research, CSIRO Publishing, Vol. 50, No. 3 ( 2022-9-19), p. 182-189
    Abstract: Context Nest predation is a leading cause of nest failure for most ground-nesting birds. Methods that allow for accurate classification of fate and identification of predators are important for understanding productivity and conservation strategies. Past studies have used a visual inspection of nest remains to determine nest fate and predict predator identity. Most formal assessments of these methods have addressed small-bodied birds nesting in trees or shrubs, and have revealed that use of evidence at nests can be relatively accurate for determining nest fate but may lead to incorrect conclusions regarding predator identity. However, few have tested the latter hypothesis for larger ground-nesting birds with precocial young. Aim We aimed to evaluate a classification system developed for determining nest fate and identifying predators of waterfowl nests, at both the scale of individual nests and across the study area. Methods From 2016 to 2020, we located 989 blue-winged teal (Spatula discors), mallard (Anas platyrhynchos) and gadwall (Mareca strepera) nests in central North Dakota. We placed cameras at a subset of 249 nests and recorded evidence of nest remains at depredated nests. Key results The most common predators were American badgers (Taxidea taxus), followed by striped skunks (Mephitis mephitis), raccoons (Procyon lotor) and red foxes (Vulpes vulpes). Using evidence of nest remains, we determined nest fates with high accuracy (98.0%). However, evidence of nest remains was only sufficient for identifying predators at 50% of nests, and the classification system was correct only 69.7% of the time. The predicted proportion of predators across the study area differed between the classification system and our video evidence as well. Conclusions The accuracy of predator identifications based upon the classification system that we evaluated was not supported at any scale. Implications Our results suggest that evidence of nest remains can be used to determine nest fate for large-bodied precocial, ground-nesting birds, but accurate identification of nest predators will require alternative methods such as nest cameras.
    Type of Medium: Online Resource
    ISSN: 1035-3712 , 1448-5494
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2022
    SSG: 12
    SSG: 23
    Location Call Number Limitation Availability
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  • 3
    In: Wildlife Research, CSIRO Publishing, Vol. 50, No. 4 ( 2022-11-8), p. 272-282
    Abstract: Context Across much of its geographic range, the masked water snake, Homalopsis buccata, is harvested each year in large numbers, questioning the sustainability of that offtake. Aims To quantify abundance and demography of water snakes in anthropogenically disturbed habitats in an area of West Java, where these snakes are subject to intensive harvest. Methods We accompanied professional snake-collectors, and conducted our own surveys of ponds and irrigation canals, to record the numbers and attributes (species, sex, size, etc.) of snakes that were captured using a variety of methods. Key results Snakes of several species were abundant, with mean capture rates of 32 666 snakes km−1 of irrigation canals, and 57 501 snakes km−2 of fishponds (9500 and 43 788 for H. buccata alone). Sex ratios of H. buccata were female-biased in ponds but not irrigation channels. Ponds underlain by deeper mud contained more snakes. Collecting methods varied among habitat types, in a way that reduced collateral risk to commercially farmed fish in ponds. Conclusions These water snakes are extremely abundant in Java, despite high levels of historical and continuing harvest. The inference of low population sizes for H. buccata in Indonesia, as presented in the IUCN Red List, is erroneous. Implications An ability to utilise anthropogenic resource subsidies (in this case, fish farmed in village ponds) allows some native predator species to attain remarkably high abundances, and to withstand intense efforts at harvesting.
    Type of Medium: Online Resource
    ISSN: 1035-3712 , 1448-5494
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2022
    SSG: 12
    SSG: 23
    Location Call Number Limitation Availability
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