Notiosorex and Diplomesodon, however, are found in arid regions, though their exact habitats are not definitely known. Because of the small size of shrews, temperature and evaporation may be of more importance in governing the distribution of this group than that of most other mammals. Shrews frequently have markedly restricted habitats. They are mainly terrestrial, but some take to water freely, and others burrow a little. There are records of tree climbing by Blarina and Sorex.
Most forms travel at a swift run.
Some experiments with the oxygen consumption of shrews have demonstrated a higher metabolic rate at rest than for various wild mice and voles of the same weight. Other experiments, however, indicate that shrews have a metabolic rate comparable to that of other mammals of the same size. It has been suggested that the high rates of oxygen consumption exhibited by the shrews in the former group of experiments are due to external factors such as nervous stimulation rather than to higher inherent rates of tissue metabolism. Shrews are generally solitary except when they pair off during the breeding season. One exception is Cryptotis parva, a species that is somewhat gregarious and colonial.