Searching for Shrews
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The purpose of this project is to increase monitoring of small mammals in Great Britain, especially shrews. The greater white-toothed Shrew (GWTS) has now been identified in Sunderland and is known to be an invasive species in Ireland, at the detriment of the pygmy shrew (a native species in the British Isles). We need to increase monitoring of small mammals to track the spread of the GWTS, and monitor the impact of GWTS introductions on native small mammals, especially pygmy shrews.
What is a shrew?
Shrews are the smallest mammals and are insectivorous, meaning they eat insects. They are voracious feeders and need to eat every two hours, or so. On the British mainland, we have three native species:
What is the greater white-toothed shrew (GWTS)?
The Ggreater white-toothed shrew (Crocidura russula) is native to Europe, North Africa and some Channel Islands. It is very similar in size to the common shrew but has prominent ears and long white hairs on the tail. Learn more about the species here.
Where in Britain have GWTS been found?
In October 2022, DNA analysis of a shrew carcass showed the GWTS to be present in the Sunderland area, North-East England. Further analysis of photographs suggested they may have been present in that area since at least 2015.
Where have they come from?
We don’t yet know the origin of these shrews in Sunderland. They could have been accidently imported from Ireland or the continent. Since shrews need to eat constantly, they would only survive such a journey if they travel with sufficient soil or other material that contains enough food to eat. We plan to investigate the possible origin with DNA sampling.
Why are we concerned?
The GWT shrew was first recorded in Ireland in 2007 (where only the pygmy shrew is present) and it appears to outcompete the pygmy shrew, which has disappeared from areas where the GWT shrew now occurs. It is therefore possible that the GWT shrew will negatively affect, or completely displace our smallest native mammal, the pygmy shrew.
What are we doing about it?
The GWT shrew is a new non-native species in Britain and might become invasive. We need to confirm its 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 promoting ways to record the presence of all shrews, so we can monitor GWT shrew distribution and any changes to pygmy shrew abundance.
How can I identify a shrew?
Shrews are hard to find and it can be difficult to distinguish between species without a close-up view! This is why we’ve created some easy identification sheets to help you. Click on the button below to see them.
How can I help?
Once you’ve identified a shrew, there are some easy ways to monitor them. We recommend that all sighting records are submitted either through:
Mammal Mapper with photographs, or;
MammalWeb for camera trap images and footage (a specific project has been set up for this purpose).
There are many ways to spot a shrew:
Camera trapping: Standard motion operated trail cameras can be easily adapted to photograph small mammals with the addition of a box. All images acquired during a camera deployment, regardless of species, should be submitted to MammalWeb.
Owl and bird of prey pellet analysis: Birds of prey regurgitate undigested fur and bones and these pellets can be examined for small mammal skulls. Learn more about disecting owl pellets here. Submit records through Mammal Mapper.
Live trapping for shrews: Setting traps can only be performed by experienced workers under a General License from Natural England. This requires the provision of suitable food and bedding. It is not recommended in cold conditions, and non-native species, i.e. GWT, cannot legally be released. We recommend this approach is only used by individuals who already have substantial small mammal trapping experience. Submit records through Mammal Mapper.
Ad hoc sightings: Pictures of shrews that have been brought home by cats, or sightings of dead shrews in the wild can be submitted through Mammal Mapper. Although live wild shrews can be seen and reported, it is very hard to tell the difference between them and, therefore, impossible to verify if the sighted individual was a GWT shrew.
Volunteer Owl Pellet Dissection
Owls and birds regurgitate the undigestible fur and bone of their prey into neat pellets, and through pellet dissections, we can tell exactly what has been eaten – which could include a GWT shrew! We need your help to analyse owl pellets to help us along in our search for the GWT shrew.
We’re grateful to be partnering with the Barn Owl Trust to collect and analyse pellets from across the UK.
How to get involved
Do you have owl pellets on hand? If you have a stock of owl pellets or access to them, we invite you to dissect your owl pellets and send us the analysis results. Your contribution can make a significant impact on our research efforts. Please find the ‘Owl Pellet Analysis Results Template’ in the volunteer pack below, and be sure to send any findings you make to science@themammalsociety.org.
Are you interested, but need owl pellets to dissect? Whether you’re interested as an individual, or would be keen to run a workshop and engage your local community, we can help you! The dissection of owl pellets can provide valuable learning experience for all, including students at all grade levels. Reach out to us and we’ll provide you with the necessary resources – pellets, guidelines and more – to organise an educational and hands-on workshop! For more information and to express your interest, please contact science@themammalsociety.org
Can you safely and responsibly gather owl pellets? You can contribute to our Searching for Shrews project by donating them to us at Freepost MAMMALSOC. This not only helps us expand our research, but also enables more individuals and communities to get involved with owl pellet dissections!
Please adhere to the guidelines for responsible owl pellet collection provided by our partners, Barn Owl Trust.
Download pdfNote: If you do find a GWT shrew (Look out for any tiny shrew skulls and jawbones which do not have red tipped teeth! The tiny teeth will be very jagged and pointed!), please photograph each skull part as closely and in focus as possible, send these photos to science@themammalsociety.org with the pellet ID code (or location of pellet collection if you did not receive the pellet form the Mammal Society) and then wrap the skull(s) in a tissue and post with those same details and your contact information to Freepost MAMMALSOC.
For more information and resources, including our Volunteer Owl Pellet Dissection Pack and Safety Guidelines for Schools and Youth Groups, please visit our Owl Pellet Dissection page.
What should I do if I think I have seen a GWT shrew?
We encourage anyone to report sightings of live or dead shrews with photographic evidence through either Mammal Mapper, or MammalWeb. Sightings without photos can be reported through Mammal Mapper, but the exact species cannot be verified.
Thank you for showing interest in this project. It is through community science that we are able to help protect the mammals of the British Isles for future generations.