Shrew (Soricidae): small insectivorous mammals

Physical characteristics and physiology

Most shrews are very small, with compact bodies, short limbs and elongated, sensitive snouts adapted for probing leaf litter and soil. Their teeth are sharp and cusped rather than the large gnawing incisors of rodents; this dental difference (contrast with rodent incisors) reflects a carnivorous or insectivorous diet. Shrews have extremely high metabolic rates and commonly must feed many times their body weight in a day to avoid starvation. Some species have mildly venomous saliva and many produce ultrasonic calls used for orientation and prey detection.

Taxonomy and notable distinctions

True shrews belong to Soricidae. Several unrelated mammals carry the common name "shrew" because of convergent appearance: treeshrews (Scandentia), elephant shrews or sengis (Macroscelidea), otter shrews and certain West Indies shrews are placed in other groups. Genetic and anatomical studies show shrews are closer to moles (Talpidae) than to rodents (Rodentia), and modern taxonomy emphasizes these relationships.

Distribution and habitat

Shrews have a near-global distribution (worldwide) and occupy a wide range of habitats including forests, grasslands, wetlands and montane zones. Major landmasses without native shrews include New Guinea, Australia and New Zealand. In the Americas shrews reached South America relatively recently (as immigrants) and are primarily found in the northern Andes and adjacent regions (northern Andes).

Diet, behaviour and life history

Shrews are mostly insectivorous or carnivorous, feeding on insects, worms, spiders and, in larger species, small vertebrates. Their high energy demand drives constant foraging; many species are solitary and territorial. Reproduction is typically rapid: several litters per year are common, with short juvenile development and brief adult lifespans. Seasonal and microhabitat specializations appear across different species.

Ecological roles and interactions

By consuming large quantities of invertebrates, shrews influence soil and litter arthropod communities and serve as prey for birds, mammals and reptiles. In regions where they are recent arrivals (see immigrant history), shrews can affect native invertebrate assemblages and interact with introduced predators or competitors. Their small size and secretive habits mean many species are understudied.

Diversity and notable species

The family Soricidae is among the most species-rich mammal families, with many genera adapted to specialized niches. Some shrews are widespread and common, while others are narrowly endemic and of conservation concern. Local diversity is highest in temperate and montane tropical regions where insect prey is abundant.

Conservation

Conservation status varies widely. Habitat loss, introduced predators, and environmental change threaten localized endemics. Because many species are small and cryptic, assessing their populations can be difficult. Conservation measures focus on habitat protection and reducing invasive species impacts in sensitive regions.

Further reading and resources

For general introductions and taxonomic notes consult family summaries and regional faunal guides. Useful starting points cover historical groupings (Insectivora overview), modern family treatments (Soricidae), suborder discussions (Soricomorpha/Eulipotyphla), and comparisons with look-alike groups such as treeshrews (Scandentia), elephant shrews (Macroscelidea) and rodents (Rodentia). For distribution notes see global checklists (world distribution) and regional accounts for New Guinea (New Guinea), Australia (Australia), New Zealand (New Zealand), and South America (South America). Historical arrival and diversification in the Neotropics is discussed in summaries of immigrant taxa (immigrant history) and specific montane records (northern Andes).

• Key traits: small size, pointed snout, spike-like teeth, high metabolism (historical context).
• Not true shrews: treeshrews (Scandentia), elephant shrews (Macroscelidea).
• Distribution notes: absent from New Guinea, Australia, New Zealand, limited in South America.

For specialist identification, regional species lists and conservation status consult the linked resources above (Soricidae overview, suborder discussions, diversity summaries).