There are 312 species of shrew in 23 genera, which are grouped into two subfamilies. Shrews are distributed almost worldwide: of the major temperate land masses, only New Guinea, Australia, and New Zealand do not have native shrews at all; South America has shrews only in the far-northern tropical part. In terms of species diversity, the shrew family is the second or third most successful mammal family of all: being rivalled only by the rats and mice (family Muridae with about 1300 species) and one of the bat families (Vespertilionidae with 303).
In general, shrews are terrrestrial creatures that forage for seeds, insects, nuts, worms and a variety of other foods in leaf litter and dense vegetation, however some specialise in climbing trees, living underground, or even an aquatic lifestyle. All shrews are small, most no more than mouse size. The largest species is the House Shrew (Suncus murinus) of tropical Asia which is about 15 cm long and weighs around 100 grams; several are very small, notably the Pygmy White-toothed Shrew (Suncus etruscus) which at about 3.5 cm and 2 grams is regarded as the smallest living mammal.