# Shrew — Facts, Threats & Conservation

*Soricidae*

> A shrew is a small insect-eating mammal of the family Soricidae, with a long pointed snout, tiny eyes and velvety fur. Though mouse-like, shrews are not rodents but relatives of moles and hedgehogs, and are known for their extremely high metabolism and near-constant feeding.

**IUCN status:** Varies by species; most Least Concern (IUCN)  ·  **WARN range:** Europe, Asia, Africa, North America, Northern South America

## Quick facts
| Fact | Value |
| --- | --- |
| Common name | Shrew |
| Family | Soricidae |
| Order | Eulipotyphla (not Rodentia) |
| Number of species | Around 385 |
| Diet | Mainly insects and other invertebrates |
| Size | From ~3.5 cm (Etruscan shrew) to ~15 cm |
| Weight | From ~1.8 g; varies widely by species |
| Lifespan | Typically 12-30 months |
| Distribution | Almost worldwide; absent from Australia and most of South America |
| Notable trait | Some species have venomous saliva |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Mammalia
- **Order:** Eulipotyphla
- **Family:** Soricidae
- **Species:** ~385 known species

## Conservation status
- **Status:** Conservation status varies by species. As one of the largest mammal families (~385 species), shrews span the full range of risk: the great majority are assessed by the IUCN as Least Concern and remain widespread and common, but a number of range-restricted island and montane species are threatened, and a few are listed in higher-risk categories. There is no single status for the family as a whole.
- **Population:** Not estimated for the family; most widespread species are common and abundant within their ranges.
- **Trend:** Stable for most species; declining for some habitat-restricted species.
- **Assessed:** Assessed per species on the IUCN Red List; dates vary.
- **CITES:** Not generally listed on CITES (no family-wide listing).
- Local declines are linked to habitat loss, pesticide use that reduces insect prey, and predation pressure, including from domestic cats.

## Key facts: Shrew
- Shrews are not rodents; they belong to the order Eulipotyphla alongside moles and hedgehogs.
- With around 385 species, Soricidae is one of the most diverse of all mammal families.
- Their metabolism is so high that they must eat almost constantly and can starve within hours.
- The Etruscan shrew, at about 1.8 grams, is the smallest known land mammal on Earth.
- A handful of shrew species have venomous saliva, a rare trait among mammals.
- Cats and other predators often kill shrews but rarely eat them, deterred by scent glands.

## Are shrews rodents?
No. Although shrews are roughly mouse-sized and superficially resemble mice, they are not rodents and are only distantly related to them. Shrews belong to the order Eulipotyphla, a group of small insect-eating mammals that also includes moles, hedgehogs and the moles' close cousins. Rodents, by contrast, belong to the order Rodentia and include mice, rats, voles and squirrels. The easiest way to tell a shrew from a mouse is the head: shrews have a long, mobile, pointed snout that extends well beyond the mouth, very small eyes and small ears often hidden in fur. Their teeth are another giveaway. Rodents have a single pair of large, ever-growing, chisel-like incisors used for gnawing, whereas shrews have many small, sharp, spike-like teeth suited to seizing insects and other invertebrates. Many shrew species also have teeth tipped with iron-rich reddish pigment. Behaviourally, shrews are hunters rather than gnawers, spending their lives searching leaf litter and soil for prey rather than chewing seeds and nuts. So while the resemblance is real, the relationship is not.

## Why do shrews eat so much?
Shrews have one of the highest metabolic rates of any mammal, a consequence of their tiny bodies. Small animals lose heat rapidly because they have a large surface area relative to their volume, so a shrew must burn fuel at a furious pace simply to stay warm. To keep that internal furnace stoked, shrews eat almost continuously, day and night, in short bursts of activity separated by brief rests. In captivity some shrews consume between half and twice their own body weight in food every day. Their diet is dominated by invertebrates such as insects, larvae, earthworms, spiders, woodlice and snails, though some take small amounts of seeds or carrion. This relentless appetite has a stark consequence: many shrews can starve to death within a matter of hours if they cannot find food, and they rarely survive long without eating. Their hearts beat extraordinarily fast and they remain active through much of winter rather than hibernating, because stopping to sleep deeply would risk running out of energy entirely. Constant feeding, in short, is not greed but survival.

## Are shrews venomous, and can they hurt people?
A small number of shrew species are genuinely venomous, which is remarkable because venom is rare among mammals. The venom is delivered through grooves in the teeth via the saliva, and is used to subdue prey rather than for defence. In the American short-tailed shrew, the venom is potent enough that, in laboratory studies, the quantity from a single animal has been measured as sufficient to kill many small rodents by injection. The venom helps shrews tackle prey larger than themselves and, in some species, may even allow them to paralyse and store live invertebrates for later. For humans, shrews pose very little danger. They are tiny, secretive and not aggressive towards people, and a bite from a venomous species would at most cause local pain and swelling rather than serious harm. Far from being a threat, shrews are valuable allies in gardens and farmland, where their voracious appetite for insects, slugs and other invertebrates helps keep populations of garden pests in check throughout the year.

## Why do cats kill shrews but not eat them?
Cat owners often find a dead shrew left as an uneaten 'gift' on the doorstep, and the reason lies in the shrew's chemistry. Shrews possess scent glands, particularly on their flanks, that produce a strong, musky, distasteful odour. Cats are highly motivated to hunt small moving animals by instinct, so they readily catch and kill shrews, but the unpleasant smell and taste usually stop them from actually eating the catch. The result is a steady supply of intact shrew bodies delivered by domestic cats but left untouched. This behaviour is so consistent that cat predation is a recognised pressure on local shrew populations in some areas. Beyond cats, shrews fall prey to owls and other birds of prey, which have a poorer sense of smell and are far less deterred by the scent, making them among the shrew's most important natural predators. The same defensive odour that frustrates a cat does little to protect a shrew from a hunting owl swooping silently overhead at night.

## Shrew vs mouse: how to tell them apart
| Feature | Shrew | Mouse |
| --- | --- | --- |
| Group | Eulipotyphla (insectivore) | Rodentia (rodent) |
| Snout | Long, pointed, mobile | Shorter, blunter |
| Eyes | Very small | Larger, prominent |
| Teeth | Many small spike-like teeth, often red-tipped | Large gnawing front incisors |
| Diet | Mainly insects and invertebrates | Mainly seeds, grains and plants |
| Smell | Strong musky odour from scent glands | Mild musky odour |

## What WARN does
World Animal Rescue Network does not run field projects dedicated specifically to shrews, which are widespread and mostly secure, and most live well outside WARN's five partner countries. This guide is part of WARN's free educational work, which aims to make accurate, well-sourced wildlife information freely available to everyone. The threats that touch shrews most, chiefly habitat loss, pesticide use and the decline of insect prey, are the same pressures bearing down on many of the animals WARN does directly protect.

If our free wildlife guides help you see small creatures like the shrew a little more clearly, a small gift helps us keep this knowledge open to all and support the animals in our care.

## Frequently asked questions: Shrew
### Is a shrew a mouse or a rodent?
Neither. A shrew is not a rodent and is not closely related to mice, despite looking similar. Shrews belong to the order Eulipotyphla and are relatives of moles and hedgehogs, while mice are rodents. You can tell them apart by the shrew's long pointed snout, tiny eyes and many small spike-like teeth, rather than a rodent's large gnawing front incisors.

### What is the smallest shrew, and the smallest mammal?
The Etruscan shrew is the smallest shrew and the smallest known land mammal by mass, weighing only about 1.8 grams and measuring around 3.5 centimetres in head-and-body length. It is so small it can rest in a human palm. Only certain bats rival it for the title of smallest mammal, and the Etruscan shrew remains the lightest terrestrial mammal known to science.

### Do shrews eat all the time?
Almost. Because of their tiny size and very high metabolism, shrews burn energy extremely fast and must feed in short bursts throughout the day and night. In captivity some eat between half and twice their own body weight in food daily. They feed mainly on insects, worms and other invertebrates, and can starve within a few hours if they cannot find enough to eat.

### Are shrews dangerous or venomous?
A few shrew species are venomous, delivering venom through their saliva to subdue prey, which is unusual among mammals. The American short-tailed shrew is a well-known example. However, shrews are not dangerous to people. They are tiny, shy and non-aggressive, and at worst a bite from a venomous species would cause minor local pain and swelling rather than any serious injury.

### Why does my cat bring me dead shrews but not eat them?
Shrews have scent glands that produce a strong, musky, unpleasant smell and taste. Cats hunt and kill them on instinct, drawn by the small moving animal, but are then put off eating them by the odour. This is why cats so often leave intact shrew bodies as uneaten 'gifts'. Owls, which have a weaker sense of smell, are far less deterred and readily eat shrews.

### How long do shrews live?
Shrews are short-lived animals. Most live only around 12 to 30 months, and few survive much more than a year in the wild. Their frantic metabolism, constant need to feed and heavy predation pressure all keep lifespans brief. Many shrews born in one year breed the following spring or summer and die soon after, so generations turn over very quickly compared with longer-lived small mammals.

## Sources
- [Shrew - Wikipedia](https://en.wikipedia.org/wiki/Shrew)
- [Etruscan shrew - Wikipedia](https://en.wikipedia.org/wiki/Etruscan_shrew)
- [Shrew - Encyclopaedia Britannica](https://www.britannica.com/animal/shrew)
- [Soricidae search - IUCN Red List](https://www.iucnredlist.org/)
- [Eulipotyphla - Wikipedia](https://en.wikipedia.org/wiki/Eulipotyphla)

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Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/shrew