Using non-invasive and minimally-invasive methods to inform conservation of terrestrial mammals: A review of novel techniques and new applications

Abstract

Robust and reliable data underpin mammalian conservation, including priority setting, informing interventions, and measuring success. However, because many terrestrial mammals are nocturnal, crepuscular, or cryptic, obtaining data can be challenging and expensive. Problems are often magnified when focal species are rare or occur at low density and methods that involve direct intervention or create disturbance can have ethical implications. Use of non-invasive or minimally-invasive methods to survey mammals is not new. However, such approaches are continually developing and although there have been reviews for particular mammalian guild/location combinations, or for specific techniques, to date there has been no overarching review within the specific context of mammal conservation. In this review, we evaluate innovative techniques with broad applicability across mammalian taxa, habitats and contexts that have recently advanced substantially: technological approaches (camera trapping, bioacoustics, thermography, unmanned aerial vehicles); indirect methods (footprints, hair), novel approaches (detection dogs; eDNA metabarcoding), and participatory methods (technological citizen science, iEcology). We consider recent advancements, residual challenges, and take a horizon-scanning approach to highlight future development, empirical testing, and optimisation needs. Key findings include: advances in scalability of novel techniques are often due to development of open-source devices and programming interfaces; use of AI for species identification and quantification is already revolutionizing workflows; and rapid ongoing development of statistical models and analysis tools is broadening data processing potential and elevating utility of data collected using non/minimally-invasive methods beyond presence-only applications. We encourage practitioners embrace emerging tools in the conservation toolbox and to continue developing novel techniques.