Camera-trap evidence that the silver-backed chevrotain Tragulus versicolor remains in the wild in Vietnam

Nguyen, An; Tran, Van Bang; Hoang, Duc Minh; Nguyen, Thi Anh Minh; Nguyen, Dinh Thang; Tran, Van Tiep; Long, Barney; Meijaard, Erik; Holland, Jeff; Wilting, Andreas; Tilker, Andrew

doi:10.1038/s41559-019-1027-7

Cited by 20 publications

(14 citation statements)

References 23 publications

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“…Camera traps are the standard tool for assessing population status of many terrestrial mammals, describing species distributions, and confirming the presence of some of the rarest terrestrial species (e.g. [1,2]). Camera traps log detections of all species that trigger the sensors, including rare detections of previously unknown species (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Camera traps log detections of all species that trigger the sensors, including rare detections of previously unknown species (e.g. [2]). It has been assumed that species that overlap in their geographic ranges and are considered sympatric in some areas can be effectively detected under survey designs that do not necessarily take into consideration behavioral micro-habitat preferences.…”

Section: Introductionmentioning

confidence: 99%

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Long-term monitoring of margays (Leopardus wiedii): Implications for understanding low detection rates

2021

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Population assessments of wide-ranging, cryptic, terrestrial mammals rely on camera trap surveys. While camera trapping is a powerful method of detecting presence, it is difficult distinguishing rarity from low detection rate. The margay (Leopardus wiedii) is an example of a species considered rare based on its low detection rates across its range. Although margays have a wide distribution, detection rates with camera traps are universally low; consequently, the species is listed as Near Threatened. Our 12-year camera trap study of margays in protected broadleaf forest in Belize suggests that while margays have low detection rate, they do not seem to be rare, rather that they are difficult to detect with camera traps. We detected a maximum of 187 individuals, all with few or no recaptures over the years (mean = 2.0 captures/individual ± SD 2.1), with two-thirds of individuals detected only once. The few individuals that were recaptured across years exhibited long tenures up to 9 years and were at least 10 years old at their final detection. We detected multiple individuals of both sexes at the same locations during the same survey, suggesting overlapping ranges with non-exclusive territories, providing further evidence of a high-density population. By studying the sparse annual datasets across multiple years, we found evidence of an abundant margay population in the forest of the Cockscomb Basin, which might have been deemed low density and rare, if studied in the short term. We encourage more long-term camera trap studies to assess population status of semi-arboreal carnivore species that have hitherto been considered rare based on low detection rates.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Long-term monitoring of margays (Leopardus wiedii): Implications for understanding low detection rates

2021

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“…Uncertainty about whether a rare species is extinct or extant is common because rare species are often difficult to detect (Lee et al 2017), and it is almost impossible to determine with any degree of certainty whether or not a species is extinct (Roberts 2006). However, the rediscovery of species considered to be extinct is also relatively common (Akcakaya et al 2017), and each year two or three missing species are found again (Lee et al 2017), such as the San Quintin kangaroo rat D. gravipes in Mexico (Tremor et al 2019) and the silver-backed chevrotain Tragulus versicolor in Vietnam (Nguyen et al 2019). Nonetheless, small missing mammals like the Morro Bay kangaroo rat are disadvantaged because fewer resources (money, time, effort) are expended seeking small missing mammals than larger missing mammals (Fisher 2011;Lee et al 2017).…”

Section: Discussionmentioning

confidence: 99%

Survey for Morro Bay Kangaroo Rat: A Rare Mammal of Uncertain Status

Villablanca

Kofron

Oliver

et al. 2020

Journal of Fish and Wildlife Management

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The Morro Bay kangaroo rat Dipodomys heermanni morroensis is a small, nocturnal, burrowing rodent endemic to the vicinity of Morro Bay in San Luis Obispo County, California. It was listed as endangered pursuant to the U.S. Endangered Species Act in 1973. Despite many searches over three decades, the Morro Bay kangaroo rat has not been captured or sighted in the wild since 1986. While recognizing that the Morro Bay kangaroo rat may be extinct, Kofron and Villablanca (2016) also speculated it may be persisting at extremely low density in isolated colonies, and they recommended surveying with wildlife scent-detection dogs and baited camera traps. We searched with a wildlife scent-detection dog and baited camera traps in four historically-occupied areas and detected no Morro Bay kangaroo rats. Unfortunately our data combined with all other existing data do not allow us to conclude whether the Morro Bay kangaroo rat is extinct or extant. Essentially, the international standard has not been met to make a definitive determination of extinction. That is, a species should be considered extinct only when there is no reasonable doubt that the last individual has died (International Union for the Conservation of Nature 2012). We acknowledge that because of resource limitation we surveyed only a small sample of the numerous patches of habitat in the expansive landscape. Further, we now consider the Morro Bay sand spit (total area 4.35 km2, foredunes 3.75 km2), a peripheral area, as potentially part of the geographic range with suitable habitat, and it has never been searched. Therefore, considering all available information, we conclude that the Morro Bay kangaroo rat must be considered as possibly extant. We recommend that search efforts continue in several specific areas, including the Morro Bay sand spit. If the Morro Bay kangaroo still exists, it will be challenging and difficult to rediscover because of its likely low density and patchy distribution in the expansive landscape, combined with its small size, nocturnal nature, and secretive lifestyle.

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“…It is unsurprising then, that of the world’s 103 Caprinae, the International Union for Conservation of Nature (IUCN) considers over 70% threatened, with most lacking abundance and distribution data, thereby compounding their dire conservation status 1 . Similarly, other endangered mammals, like the recently discovered silver-backed chevrotain ( Tragulus versicolor ) and the secretive fishing cat ( Prionailurus viverrinus ) lack practical and effective techniques for acquiring abundance data, constraining conservation work 2 , 3 .…”

Section: Introductionmentioning

confidence: 99%

Accurate population estimation of Caprinae using camera traps and distance sampling

Harris

Butler

Stewart

et al. 2020

Sci Rep

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With most of the world’s Caprinae taxa threatened with extinction, the IUCN appeals to the development of simple and affordable sampling methods that will produce credible abundance and distribution data for helping conserve these species inhabiting remote areas. Traditional sampling approaches, like aerial sampling or mark-capture-recapture, can generate bias by failing to meet sampling assumptions, or by incurring too much cost and logistical burden for most projects to address them. Therefore, we met the IUCN’s challenge by testing a sampling technique that leverages imagery from camera traps with conventional distance sampling, validating its operability in mountainous topography by comparing results to known abundances. Our project occurred within a captive facility housing a wild population of desert bighorn sheep (Ovis canadensis) in the Chihuahuan desert of New Mexico, which is censused yearly. True abundance was always within our 90% confidence bounds, and the mean abundance estimates were within 4.9 individuals (average) of the census values. By demonstrating the veracity of this straightforward and inexpensive sampling method, we provide confidence in its operability, urging its use to fill conservation voids for Caprinae and other data-deficient species inhabiting rugged or heavily vegetated terrain.

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Camera-trap evidence that the silver-backed chevrotain Tragulus versicolor remains in the wild in Vietnam

Cited by 20 publications

References 23 publications

Long-term monitoring of margays (Leopardus wiedii): Implications for understanding low detection rates

Long-term monitoring of margays (Leopardus wiedii): Implications for understanding low detection rates

Survey for Morro Bay Kangaroo Rat: A Rare Mammal of Uncertain Status

Accurate population estimation of Caprinae using camera traps and distance sampling

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