Effectiveness and applications of hair traps for the study of wild mammal populations

Direct studies of wild mammals are challenging due to the difficulty for capturing and handling and the associated high costs. Thus, noninvasive hair trapping for surveying mammal populations has been widely used in wildlife ecology and management. However, the efficiency of this method may differ depending on the animal species and other different factors. Here we aimed at evaluating the potential of hair tube traps for reliable detecting mammal species as well as to assess whether type of habitat, baits, hair trap's size variables (length, diameter and time staying active) and position variables (height, altitude, orientation and location) influenced trapping success (i.e. obtaining hair samples or not) and effectiveness (i.e. percentage of successful sampling traps and the number of species detected) of hair traps. Hair traps were done with PVC tubes with adhesive tape inside, and they were placed at different locations where mammal cues were previously detected. Collected hairs were identified to species by macro and microscopic characteristics. We collected hairs in the 82% of the hair traps placed and we detected 9 species which represented 64% of the wild mammals potentially detectable with this method in the study areas. No one of the studied variables explained trapping success. However, trap's diameter significantly influenced effectiveness, but contrary to expected, the larger traps presented lower sampling success and less species were registered. Position variables did not influence effectiveness of hair traps. Sampling success due to baits used was related to diet preferences of the species. Further, trap's diameter and length, height, inclination and altitude influenced collecting hair samples from the different animal taxonomic orders. These results suggest that hair trapping can be used as a good tool for the study of wild mammals, but assumptions related to trap size and position variables should be taken into account to increase the effectiveness of this method.