• The GWT shrew is a new non-native species in Britain and might become invasive, affecting native shrews
  • DNA sampling is being planned to be able to answer where it originated from
  • Mammal Society and MammalWeb are calling for increased monitoring of small mammals, in particular shrews, in Britain
  • Since the first press release, another likely GWT shrew has been identified in Nottinghamshire from photographs taken of a dead specimen earlier this year. Indicating that monitoring of shrews should be at national extents.

In September 2022, the Greater White-toothed (GWT) shrew was discovered in Great Britain by Ian Bond, from a specimen caught by Melissa Young’s indoor cat. This new non-native mammal, found in the Sunderland area, was confirmed via a DNA test undertaken by Ecotype Genetics and Swift Ecology Ltd.

At present, the GWT shrew is not known to be invasive in Britain but, as a new non-native species, it has the ability to become invasive. The GWT shrew is known to outcompete the pygmy shrew in Ireland and there is a possibility that the GWT shrew will negatively affect, or completely displace our pygmy shrew.

“When the species was first found in Ireland in 2007, we thought that it could be a positive addition and maybe act as a new and plentiful prey source for birds of prey and other carnivores.” said Allan McDevitt of the Mammal Society. “However, we soon realised that the native pygmy shrew had completely disappeared whenever the GWT moved into an area. Obviously, we are concerned about similar problems occurring in Britain.”

The GWT shrew is native to Europe, North Africa and some of the Channel Islands. Although the origins of the shrews found in Sunderland are currently unknown, they could have been imported from Ireland or the European continent. DNA sampling is being planned to be able to answer this question.

With this in mind, the Mammal Society and MammalWeb are calling for increased monitoring of small mammals, in particular shrews, in Britain. There is a need to confirm the GWT shrews’ presence in the wild, find out how far it has spread, and determine whether it is affecting the abundance of pygmy shrews.

The Mammal Society and MammalWeb are currently promoting ways to record the presence of all small mammals, so we can monitor GWT shrew distribution and any changes to pygmy shrew abundance. We have suggested using camera traps, taking photos of sighted shrews, alive or dead, and checking owl and bird of prey pellets for shrew remains. Ad hoc sightings – ideally with photos – can be recorded using the Mammal Mapper app. Camera traps can be modified to record small mammals, and all resultant footage submitted to the MammalWeb platform.

“Camera traps placed in baited boxes and modified with close-focus lenses can yield amazing footage of small mammals,” said Philip Stephens, one of the founders of MammalWeb. “These sensors remain active 24-hours a day, yielding footage that enables experts to identify which species are where, and how they affect each other.”

Since the GWT shrew in Sunderland was first identified a number of shrew records have been reported. Recently, a photograph of a dead shrew in Nottinghamshire, submitted via the Mammal Mapper app, was reviewed by independent experts and confirmed to be a highly likely GWT shrew. This record is over 200km away from the initial GWT shrew sighting and highlights the importance of vigilance and widespread recording of small mammal species across national extents. 

Frazer Coomber Science Officer at the Mammal Society finishes “The recording of any mammal species is important as it helps us to understand their current distribution and population and how these change over time. Small mammals are under-recorded, and it is essential to collect baseline data on them. We need to know their current distribution, population and species assemblages so that we can understand the effect that GWT shrews could have on our native species. Recording mammals using the Mammal Society’s Mammal Mapper app is straightforward and anyone with a smartphone can submit a record. The ability to take photographs, alongside each record, helps to ensure species recorded can be verified accurately. So, even if you are unsure what species it is, please photograph it and report it as a small mammal.”