Accurate population estimation of Caprinae using camera traps and distance sampling

Abstract

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.

Assessing the camera trap methodologies used to estimate density of unmarked populations

“…Considering the robust theoretical framework, specific software and advice for study design, testing CT‐DS could considerably increase the applicability of camera traps for the monitoring of unmarked populations. To date, CT‐DS has been applied in a chimpanzee population (Cappelle et al., 2019), a community of species of the rainforest (Bessone et al., 2020, Cappelle et al, 2021), a bighorn sheep population (Harris et al., 2020) and a marmot population (Corlatti et al., 2020). The REM is, without a doubt, the most applied method (Gilbert et al., 2020).…”

“…To date, CT-DS has been applied in a chimpanzee population (Cappelle et al, 2019), a community of species of the rainforest (Bessone et al, 2020, Cappelle et al, 2021, a bighorn sheep population (Harris et al, 2020) and a marmot population (Corlatti et al, 2020). The REM is, without a doubt, the most applied method (Gilbert et al, 2020).…”

Cattle Grazing Effects on Vegetation and Wild Ungulates in the Forest Ecosystem of a National Park in Northeastern China

“…But, for wild ungulates which lack distinctive unique markings, camera traps could still be limited to providing an index of relative abundance rather than absolute abundance (Gilbert et al, 2020), much as we have reported here. However, new camera trap methods are emerging which may effectively estimate abundance of unmarked animals, including time-toevent and space-to-event models (Moeller et al, 2018;Loonam et al, 2020), the random encounter and staying time model (Nakashima et al, 2018(Nakashima et al, , 2020, and distance sampling with camera trap images (Howe et al, 2017;Harris et al, 2020); these and other new methods could be explored and trialed in future.…”

Perspectives on individual animal identification from biology and computer vision

“…Applied uses include those with the primary aims of describing, characterizing, and monitoring observed phenomena, including species distribution and abundance, animal movements and home ranges, or resource selection (45,78,79). These studies frequently adopt a top-down perspective in which the predominant focus is on groups (e.g., populations), with individuals simply viewed as units within the group, and minimal interpretation of individual variability.…”