Use of a novel camera trapping approach to measure small mammal responses to peatland restoration

Abstract

Small mammals, such as small rodents (Rodentia: Muroidea) and shrews (Insectivora: Soricidae), present particular challenges in camera trap surveys. Their size is often insufficient to trigger infra-red sensors, whilst resultant images may be of inadequate quality for species identification. The conventional survey method for small mammals, live-trapping, can be both labour-intensive and detrimental to animal welfare. Here, we describe a method for using camera traps for monitoring small mammals. We show that by attaching the camera trap to a baited tunnel, fixing a close-focus lens over the camera trap lens, and reducing the flash intensity, pictures or videos can be obtained of sufficient quality for identifying species. We demonstrate the use of the method by comparing occurrences of small mammals in a peatland landscape containing (i) plantation forestry (planted on drained former blanket bog), (ii) ex-forestry areas undergoing bog restoration, and (iii) unmodified blanket bog habitat. Rodents were detected only in forestry and restoration areas, whilst shrews were detected across all habitat. The odds of detecting small mammals were 7.6 times higher on camera traps set in plantation forestry than in unmodified bog, and 3.7 times higher on camera traps in restoration areas than in bog. When absolute abundance estimates are not required, and camera traps are available, this technique provides a low-cost survey method that is labour-efficient and has minimal animal welfare implications.

Estimating the density of small mammals using the selfie trap is an effective camera trapping method

“…Removing the need to directly observe or physically handle an animal has meant that monitoring them can be achieved with minimal negative impacts on the target species or populations. Traditionally, camera traps have been used to target larger terrestrial mammal species, although recently novel methods and adjustments in procedures have meant camera traps can be used to study reptiles (Welbourne 2013;Hobbs and Brehme 2017), arboreal species (Gracanin et al, 2018(Gracanin et al, , 2020Gregory et al, 2014;Whitworth et al, 2016) and small mammal species (De Bondi et al 2010;McCleery et al 2014;Villette et al 2016Villette et al , 2017Mos and Hofmeester 2020;Thomas et al 2020;Littlewood et al 2021).…”

Mapping differences in mammalian distributions and diversity using environmental DNA from rivers

“…Mammals are traditionally surveyed by camera trapping, live-trapping and/or field sign surveys (Sales et al, 2020a) with the accuracy of these methods heavily reliant on the intensity of sampling efforts and the susceptibility of species and individuals to capture/detection by each method. Each method may have additional concerns or limitations, such as ethical considerations in live-trapping (Sikes et al, 2016), surveyor expertise in correctly identifying field signs (Harrington et al, 2010) and camera trap placement (Littlewood et al, 2021;Kaizer et al, 2021). Given the wide variety of ecologies exhibited within mammals, there is clearly no 'one size fits all' method for monitoring either the entire or a significant component of the overall mammalian community.…”

Assessing environmental DNA metabarcoding and camera trap surveys as complementary tools for biomonitoring of remote desert water bodies

“…Nevertheless, there are also limiting factors for unbiased detectability of species, such as movement range (Burton et al, 2015; Caravaggi et al, 2020) or body mass. Small mammals are usually underrepresented in CT because their size is insufficient to trigger the camera sensor (Leempoel et al, 2020; but see Littlewood et al, 2021). They provide information on species' abundances, density, and richness while allowing for multispecies monitoring (Rovero & Zimmermann, 2016).…”