How to detect elusive species? Detection dogs in nature conservation

Nature conservation often faces the problem that many species are difficult to monitor. This is especially true for species that elusive, nocturnal, or hard to capture. In addition, some of those threatened species are conflict-laden at the same time [1]. Without proper monitoring data, it is challenging or even impossible to make evidence-based statements regarding these species' distributions, population status and trends which is inevitable for their conservation and management. Importantly, this does not only include small-bodied pest species but also medium-sized or large vertebrate species. For example, the Eurasian wolf (Canis lupus), the Eurasian lynx (Lynx lynx), or the Eurasian otter (Lutra lutra) are locally listed as (critically) endangered, listed in the annex IV of the European Habitats Directive, and can locally cause severe conflicts with humans. Improving monitoring methods is thus highly important. Monitoring of a species can be done through visual or acoustic observations or through evidences that the species was present in the recent past, such as tracks, scats, or hair. Evidence-based monitoring has the advantage that it is non-invasive and thus harmless. It can be done by humans but also with support of special detection dogs, such as scat, den, or roost detection dogs. While in former times dogs have been used for hunting, since the last century, they are increasingly used to detect rare or elusive species and their evidences. The use of wildlife detection dogs is particularly well established in America, New Zealand, Australia, and Africa, but also European monitoring projects increasingly deploy detection dogs. We tested the advantages of scat detection dogs in the Eurasian otter and found that detection dogs were more likely to find the scat of the correct species than humans visually searching for scat. Moreover, detection dog teams were twice as fast and collected three times more scats. In a review of almost 600 publications, we then looked for general advantages and disadvantages of wildlife detections dogs. We found that in most studies detection dogs increased efficiency making it a cost-effective method. Some authors claimed that the species would not have been found without detection dogs. Also, their well-developed olfactory sense allowed dogs to differentiate much clearer between signs of related species reducing false detections. Occasionally, a combination with other methods, such as cameras, hair sticks, or live-trapping, was suggested. Only in <1% of all studies, detection dogs performed worse than other monitoring methods, mainly due to inappropriate training or too dense vegetation where dogs could either not enter or not search freely. We conclude that given proper training, wildlife detection dogs can significantly increase both data quantity and quality in species monitoring. [1] Klenke et al. 2013. Human-Wildlife Conflicts in Europe. Springer. One detection dogs alterting at otter scat.peerReviewe