How to mask human scent

Submitted by editor on 23 September 2014.

Camera traps have become a widely used survey tool that is implemented to answer a variety of ecological questions. In all types of camera trap studies, maximizing detection of wildlife is an important concern, and there are many methodological biases that have to be addressed. Past studies suggest many possible problems that may reduce the efficacy of camera trap surveys. Of the many technical and procedural considerations, one particular topic grabbed our attention: how does human scent at camera trap locations impact wildlife detection rates and the number of captures? In our paper “Do available products to mask human scent influence camera trap survey results?” we attempt to answer this question. While many other methodological questions regarding the implementation of camera traps have been addressed by researchers in the past, we offer the first look at how available scent-covering technology impacts camera trap studies. To explore our research question and hypotheses, we conducted a manipulative experiment for approximately 12 months in North Carolina (USA). This involved deploying cameras in two treatments. In one treatment, research scent was masked with commercially available products while servicing camera traps. No attempt was made to mask scent while servicing cameras in the other treatment.

The suite of scent-covering products we used: scent adsorbing clothing, scent covering soaps and detergents, scent-adsorbing storage bag. Endearingly referred to as the “ninja suit”

Scent and odors are notoriously difficult to study in a natural setting, and our results reflect the subtle effect scent may have on wildlife. Additionally, our study illuminates complex relationships between wildlife and a human enforced “landscape of fear”. In other words, is it possible for human scent to induce a base level of “fear” among animals that perceive human presence as a threat? From the results that we found, it is likely that this fear varies by species and time of year. Nonetheless, we were able to detect a significant treatment response of white-tailed deer (Odocoileus virginianus) at one of our study sites. For this species, cameras traps that received our “human scent masked” treatment had higher capture rates compared to cameras that were maintained in the “unmasked” treatment.

Maintenance on camera traps involved swapping out memory cards and checking battery life. To minimize confounding of treatments, we followed specific GPS routes to stay far away from cameras in the opposite treatment. Here, we mimic the typical researcher in our scent “unmasked” treatment.

Further research is needed to distinguish between the impact of human scent and the efficacy of scent-covering products. We believe our research is a starting point, and we suggest future avenues of study regarding human scent, scent-covering products, and camera traps. We also discuss how human scent may play a larger role in projects that study species that are highly wary of human presence. Overall, implementing some sort of scent-covering product may be beneficial in ensuring higher detection rates of wildlife.

It is likely that species that are generally more wary of human presence, such as canids (like this coyote, Canis latrans) and felids, may avoid camera traps with human scent on and around them.

The authors through David Munoz