Greater white-toothed shrew

The greater white-toothed shrew is a large shrew with a greyish-reddish brown upper/dorsal surface and a yellowish-grey underside. This shrew is a non-native species that was only discovered in the British Isles in 2021, by a cat named Jeff!  

Taxonomy chart

Animalia - Chordata - Mammalia - Eulipotyphla - Soricidae - Crocidura - C. russula

Conservation status: UK Red List

GB: N/A 

England: N/A  

Scotland: N/A 

Wales: N/A  

Global Least Concern 

Summary

Diet: Insectivorous. Woodlice, snails, slugs, spiders, earthworms, caterpillars, occasionally small rodents, lizards, and amphibians.  

Habitat: Hedgerows, grassland, woodland, cultivated areas, and human settlements in the colder months. 

Size: Weight: 5-16g Size: 44-86mm with a tail of 24-47mm.   

Lifecycle: Live up to 18 months, 30 in captivity. Individuals live through one breeding season between March and September and have up to 4 litters of 2-10 young. 

Conservation concerns: The greater white-toothed shrew is a non-native species and thus is not of conservation concern in the UK, though it potentially causes conservation concerns to other species, such as our native pygmy shrew, which it has displaced in Ireland, where it is also a non-native invasive species. 

Terminology   

Female-biased dispersal: When females leave their birth/home site in order to find mates to breed, which is thought to prevent inbreeding. 

Diurnal: Animals which are mostly active during the day. 

Echolocation: A process by which animals detect the location of objects around them (especially in the dark) by projecting sound waves and using the echoes to navigate or find prey. 

Insectivorous: Animals that feed on insects, worms and other invertebrates. 

Geography   

The greater-white toothed shew is native to Europe and islands such Guernsey, Alderney and Herm. It was discovered in Ireland in 2008, and in Sunderland, North-East England, in 2021. The Mammal Society is currently tracking its spread, and it has now been confirmed to be in Nottinghamshire as well as Sunderland. 

Greater white-toothed shrews inhabit hedgerows, grassland, woodland, cultivated areas and woodland with a preference for human settlements and farm buildings during the colder months.  

Biology  

Greater white-toothed shrews can grow to a length of 44-86mm, with a tail of 24-47mm. They weigh approximately 5-16g. 

Covered in a grey-red-brown upper half and a yellowish-grey underside, greater white-toothed shrew have prominent ears, bright white teeth, and a tail with long, white hairs, which inspired their genus name ‘crocidura’, the Greek word for ‘woolly tail’. 

Greater white-toothed shrews can live up to 18 months in the wild and 30 in captivity. They are monogamous and show female-biased dispersal, meaning that females leave the site where they were born in order to breed, which is thought to help prevent inbreeding. Female-biased dispersal is usually uncommon in mammals. Greater white-toothed shrews typically live through one breeding season, which occurs from March to September, and females have up to 4 litters of 2-10 young, which are cared for by both parents. Shrewlets remain in their parental territory until the following breeding season and reach sexual maturity at around 50-78 days old. 

Ecology   

Greater white-toothed shrews are an insectivorous species, feeding on a wide range of invertebrates including woodlice, snails, slugs and spiders. They also munch on caterpillars and earthworms, especially in the winter, and have been occasionally known to consume larger animals, such as small rodents, lizards, and amphibians. 

As a semi-social species of shrew, greater white-toothed shrews live in close proximity to each other and have even been found to nest together in groups. They construct open, saucer-shaped nests from dry grass, usually under stones, logs or inside abandoned burrows. Mated pairs will often guard their territory together. Greater white-toothed shrews are mostly diurnal – active during the day – and even use a primitive form of echolocation to communicate and interpret their environment. They are very vocal and will make high-pitched squeaks when threatened or alarmed, as well as twitters and snuffles when foraging. Their main predators are barn owls, stoats, and domestic cats, though their dark colouring allows them to camouflage under leaf litter to hide from predators. 

Conservation   

Greater white-toothed shrews are considered a non-native species in the British Isles and thus the UK Red List does not apply to them. 

In Ireland, greater white-toothed shrews were discovered in 2008 and have since displaced Ireland’s native pygmy shrews, which are three times smaller than themselves. Greater white-toothed shrews start off by eating larger insects but progress to eating small insects, which is what pygmy shrews directly rely on – thus outcompeting and displacing them.  

Mammalogists are concerned that greater white-toothed shrews could displace our native small mammal species and impact habitats and biodiversity in Britain, as they have done in Ireland. Currently, research is underway to assess the impact of the greater white-toothed shrew in Britain, including through the ‘Searching for Shrews’ survey, where owl pellet dissection is being undertaken to identify their spread.  

History   

Greater white-toothed shrews were only discovered in Ireland in 2008 and in Great Britain in 2021, but are native to Europe and North Africa.  

After appearing in Ireland in 2008, greater white-toothed shrews spread rapidly, leading to the displacement of pygmy shrews. The first greater white-toothed shrew in England was originally found by a cat named Jeff, belonging to a Sunderland-based Mammal Society supporter, in 2021. Jeff’s owner posted a picture of the unknown shrew on a Facebook group, which was promptly identified as a greater white-toothed shrew by ecologist Ian Bond. Concerned that the greater white-toothed shrew could displace our native small mammal species and impact habitats and biodiversity, such as they did in Ireland with the pygmy shrew, mammalogists immediately set up the ‘Searching for Shrews’ project to start a nationwide search for these shrews. Since shrews are difficult to survey for, the 'Searching for Shrews' project encourages volunteer citizen scientists to analyse barn owl pellets collected from sites all around the UK. As a result of this project, the greater white-toothed shrew has recently been found to have spread throughout Country Durham as well as to Nottinghamshire. 

Identification and surveying 

Unpigmented teeth: Greater white-toothed shrews have bright white teeth due to a lack of iron deposits, whilst other shrew species have red-brown-orange tips (except lesser white-toothed shrews, which are only found on the Isles of Scilly, Jersey, and Sark). 

Prominent ears: Greater white-toothed shrews have more prominent ears than other shrew species. 

Surveying period: The main surveying method for shrews, which involves dissecting owl pellets, can be done year-round. Trapping shrews is only allowed under licence and requires special measures to be in place due to the fact that they need to feed every few hours. Small mammal traps such as Longworth traps can be supplied with ‘shrew holes’ that are small enough to allow shrews to escape if they get trapped. 

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