Using camera traps to estimate ungulate abundance: a comparison of mark–resight methods

Abstract

Many global wildlife populations are experiencing unprecedented declines. Estimates of population abundance are needed to effectively manage common species and to conserve vulnerable species. Camera traps have advanced as wildlife monitoring tools for ungulates and can provide improved methods of estimating population abundance. Little is known, however, about how camera traps set for ungulates compare with traditional methods (e.g., ground and aerial surveys) used simultaneously. From 2012 to 2014, we captured and radio collared 34 female and 32 male bighorn sheep (Ovis canadensis) in a closed population in Utah, USA. Each collar had a unique letter and number combination. We then estimated number of young, females and yearlings, males and population abundance using multiple methods simultaneously: helicopter surveys, resight surveys performed from the ground, camera trap surveys using marked but not individually identifiable individuals and camera trap surveys using marked and individually identifiable animals. All methods estimated similar abundance. Across years, ages and sexes, however, camera trap surveys produced the most consistent and precise estimates of abundance for adult females and yearlings, lambs and the population. That method was less intrusive and safer than helicopter surveys. Our results indicate that camera trap surveys using photographs of marked animals in which the majority of the population visits a specific resource can produce precise estimates of abundance that are safer, as well as less intrusive and expensive than traditional methods. Using camera traps also creates a permanent record of photographs that can be archived and reanalyzed to answer future ecological and population questions. Finally, this method of estimating abundance can be used in other areas with ungulates that congregate around resources (e.g., watering sites or mineral licks).

Estimating roe deer density using motion‐sensitive cameras in Switzerland

“…During the pilot survey, only a small number of females could be identified by natural markings (i.e., molt in spring), which vary over time, increasing the likelihood of misidentification. Therefore, to further validate our approach, a representative proportion of female roe deer should be marked with GPS collars with a unique letter and number combination or ear tags (Taylor et al 2021) in a future study. This would allow us to estimate female density using generalized spatial mark‐resight models (Whittington et al 2017, Efford and Hunter 2018).…”

Population dynamics and the effect of drought in the threatened Nubian ibex

“…Camera traps present a technological advance that can mitigate some of the challenges facing practitioners in attempts to estimate abundance and other state variables of populations inhabiting remote and inaccessible terrains (Taylor et al 2022). But applying robust methods to camera trap data often requires costly and time-consuming marking effort.…”

“…Mountain ungulates typically inhabit remote, inaccessible, and structurally‐complex landscapes, making estimation of population size and other state variables, while accounting for imperfect detection, a challenging task. In deserts, however, mountain ungulates are often seasonally dependent on perennial water sources, which provides an opportunity for the application of techniques using camera traps (Taylor et al 2022).…”

I Spy Through a Camera’s Eye: Divii in the Gwich’in Settlement Area

“…My MSc research aims to evaluate the effectiveness of camera traps as a novel alternative or compliment to aerial surveys in ways previously never studied for wild sheep. Using remote wildlife cameras to determine divii population demographics and species interactions on the landscape could revolutionize wild sheep research and management by providing a non-invasive, cost-effective tool that produces far more data than the status quo helicopter surveys (Taylor et al, 2022). Further, camera arrays have potential to be further networked across massive landscapes to achieve larger and more robust monitoring goals.…”

“…Remote wildlife cameras, on the other hand, are an emerging non-invasive survey method that provides continuous sampling of entire mammal communities, which can be further evaluated to model population changes over time in relation to environmental variables and interactions among multiple species (Burton et al, 2015;Caravaggi et al, 2020;Kays et al, 2020). Using remote wildlife cameras to derive and model critical wild sheep population demographics is a novel application of the method (Taylor et al, 2022) and may serve as a viable alternative to aerial surveys.…”