Review of Capturing Techniques for Otters (Lutrinae) and Testing Lure Effectiveness for Eurasian Otters (Lutra lutra)

Abstract

To learn more about a species’ behavior and ecology, individuals sometimes have to be trapped, either invasively with restraining traps or non-invasively with camera or hair traps. The use of attractants such as scent lures can help in attracting animals to the trap site. In research on otters, various of these methods and scents are used, which this study summarizes with a focus on effectiveness by conducting a systematic literature review according to the updated PRISMA guidelines. Furthermore, an experimental camera trap study on the effectiveness of sardines, mink musk and otter spraints as scent lures for Eurasian otters (Lutra lutra) was carried out in fall and winter of 2023. The systematic literature review identified seven different main trapping methods (net traps, leghold traps, cage traps, suitcase traps, hair traps, and camera traps with lures), as well as different attractants for hair and camera trap studies being used. Due to limited comparability of the included studies, no most effective method could be identified, although it is suggested that trap placement might influence trap effectiveness more than attractants. The experimental camera trap study resulted in 320 observations of animals, nine of which were of otters. A Friedman test showed no significant differences between the different lures in the number observations of Eurasian otters, nor in the time they spent at a site. There were also no significant differences in observations detected in other species, but American mink (Neovison vison) spent significantly more time at a site, when any lure was used compared to times where no lures were used. This thesis highlights the need for more research on otter trapping with a focus on the use of scent lures, trap placement and animal welfare to be able to trap them in the most effective and least harmful way.