- Obtaining reliable data on small mammal population structure and numbers requires efficient traps that trap all functional categories of the population. We compared three types of live-traps (Ugglan, Sherman, Longworth) in a pairwise comparison in two arid environments, the Negev Desert in Israel and in south-eastern Australia. Ugglan traps did not capture a single gerbil in the Negev whereas Sherman traps captured probably all resident gerbils in the trapping grid in ten trap nights. Significantly more mice were captured with Longworth traps than with Ugglans in arid and open Australian grain-growing area. Ugglan traps have a very high trapping efficiency in boreal habitats with a dense undercover, but seem to be inefficient in arid and open environments.