Protocols for field and laboratory rodent studies - HAL

1- Trapping rodents1. Trapping rodents(All authors)1.1. Trapping techniquesDifferent methods have been used for generations for catching rodentsshowing the great ingenuity of rural populations and their knowledge ofanimal behavior. Traditional techniques are quite similar in differentcountries. Recently the commercialization of trapping devices tends togeneralize the use of a few techniques to the detriment of ancestralpractices.A variety of traps have been created to catch rodents. The mostcommon are:- Live-traps: cage-traps (usually locally made, but alsocommercialized ones such as Ugglan traps), box-traps (likeSherman, Tomahawk, Longworth) and pitfall traps.- Kill-traps: snap traps, snares.These different traps vary in size and may consequently be intended totrap different sized animals. The smallest rodents and insectivores,such as Mus sp. and Crocidura sp., may escape from the cage-traps(depending on the size of the mesh fence). Box-traps have theadvantage of protecting captured animals against rain and otheranimals, but they may repel some species.Figure 2: Hunter with traditional trap inPhrae, Thailand (Photo: Herbreteau V.)Locally-made traps, usually cage-traps, may be chosen because oftheir low cost (compared with commercial ones) and because of theiravailability in remote areas. Some live-traps can fold flat to be easilycarried and stored. Others allow multiple captures (Fig. 3). Fences aresometime used to drive the animals into the trap and help to increasethe trapping success.Live-trapping is required when animals must be released (demographicstudies) and when specific tissue samplings or blood are required(medical studies). Also, kill-traps may damage animals and preventcertain analyses. For instance, snap traps usually destroy skulls andprevent any measurements for morphometrics.Figure 3: A multiple-capture cage-trap inCambodia (Photo: Herbreteau V.)Kill-traps are more effective in catching many species. They have the advantage of being cheap and small. Theyare often chosen by hunters who use large numbers of traps every night. There is a large variety of traps made bylocal people, using bamboo, wood and motorcycle tubes (Fig. 2 and 4). The trapping must be conductedcautiously. One should wear protective equipment (mask and gloves) to avoid contamination with blood orexcretions from the animal. When required, animals should be killed rapidly after their catch.Figure 4: Preparation of collars mounted on a wooden stick, in Kalasin province, Thailand (Photo: Herbreteau V.)The traps should be placed so that the captured animals are protected from changing weather conditions andpredators. Adding a shelter made with vegetation on the trap can help protecting captured animals.The choice of baits to attract rodents into the trap usually generates great debates among scientists and localpeople. Different baits can be used in a single trap to be more appealing. Each hunter may recommend their ownrecipe but differences in trapping success are not so obvious. Nevertheless some bait is advantageous in that it islong lasting and easily cleaned. Bait attracting ants should be avoided.There are other techniques for catching rodents yet some of them are more or less recommended. Diggingburrows can be a solution when the species is rarely caught using traps. However animals may escape or theycan bite easily. Glue traps and foothold traps are not recommended since they can hurt animals and becausethey can capture non-target species.3