Mammal Society marks start of ‘harvest mouse survey season’ with an urgent appeal for volunteers, and announcement of the UK’s first ever ‘National Harvest Mouse Day’ on 19th October
1st October 2025 – for immediate release
The fourth survey season of the National Harvest Mouse Survey runs from 1st October 2025 to 31st March 2026. Volunteers search for the now empty nests of harvest mice in long grass and reeds to confirm presence.
Volunteer participation in the survey dropped last year, and the charity is putting out an urgent appeal for surveyors to help – especially in areas of the country that currently have no survey data.
Surveying is fun and easy with no qualifications required. Families, schools and youth groups can get involved.
To build awareness of the importance of the harvest mouse and this survey, the Mammal Society has launched a National Harvest Mouse Day on 19th October, and hopes people will mark it by learning about this amazing animal and getting out into their local landscape to survey for nests.
October marks the start of the survey season for the National Harvest Mouse Survey, run by the Mammal Society – the only UK charity dedicated to the study and conservation of all native mammals.
Throughout the Autumn and Winter, volunteers will brave the cold to search fields, reed beds and hedgerows across England, Wales and Scotland for the distinctive spherical nests woven from grass that will now have been vacated by the mother and newly weaned pups.
The survey launched in 2021 in response to the findings of the Mammal Society’s review of the population and conservation status of British mammals (Mathews et al. 2018), which revealed that the conservation status of the smallest British rodent could not be determined due to a lack of robust data.
Monitoring small mammals such as mice, shrews and voles is difficult and time-intensive due to their diminutive size, fluctuating local populations, and elusiveness. However small mammals are essential to healthy ecosystems, due to their role in forming and maintaining healthy and well drained soil, seed dispersal, keeping insect populations in balance, and their vital importance as prey for raptors and larger mammals. Harvest mice are Britain’s smallest rodent, and the only native mammal to have a prehensile tail (meaning they can use it as a limb to hold on to branches when climbing). There is evidence that harvest mice are indicators of healthy ecosystems, meaning that data on their presence is important to guide conservation and land management decisions.
Surveying for nests in the winter, when they are no longer occupied and therefore the animals themselves will not be disturbed, is a citizen science action suitable for all ages, requiring no previous experience or naturalist qualifications. The Mammal Society provides free training and simple guide resources to support those organising a survey in their local area, or going out as an individual to conduct a survey.
The first survey season of the National Harvest Mouse Survey attracted participation from over 300 volunteer surveyors and resulted in over 500 site surveys and a wealth of data on harvest mouse presence and absence. Year 2 attracted even more volunteer effort and strengthened the data set further. However in the past two years the Mammal Society has seen a decline in volunteer effort, and is urgently seeking support from public to help build a clear picture of the current range of this important mammal.
In the last survey season (2024-5) the number of surveys decreased to a low of 298 (down from 435 on the previous year), which is attributed in part to challenging weather conditions during the peak survey season. Several areas of the country that contain potential harvest mouse habitat had limited or no survey activity – including Lincolnshire, Nottinghamshire, Cambridgeshire, west Somerset, North Devon, North Wales and central Scotland.
The first ever National Harvest Mouse Day will take place on 19th October 2025, with local volunteers encouraged to get out and conduct surveys, and to use the opportunity to raise awareness of harvest mice and their importance to healthy ecosystems.
Thanks to some areas with high volunteer effort in successive years, it has been possible for the Mammal Society to investigate the link between harvest mouse presence and habitat suitability, and a map has been produced that shows the results of a model to predict where in the country harvest mice are most likely to be found. However with data still lacking from many parts of the country, it is vital that volunteers survey sites across the country in order to test the model and allow it to be strengthened to the point when it can help land owners and ecologists anticipate the presence of harvest mice, or identify if their lack of presence is a cause for concern that requires investigation or intervention.
“Every record submitted by volunteers helps us build a clearer picture of harvest mouse distribution and the habitats they rely on, which is vital for their conservation. Personally, I think taking part is also a great way to meet like-minded people, and surveying is a fun and rewarding way to spend quality time outdoors with friends and family.”
Afrika Priestley, Data & Research Officer, The Mammal Society
“Work to protect and restore nature depends on good data that reveals what is happening in our ecosystems. Every volunteer who dons their wellies and gets out in a field to search for harvest mouse nests is a conservation hero. Just as with the important role of the smallest mammals in our ecosystems, lots of small actions add up to big impact.”
Matt Larsen-Daw, CEO, the Mammal Society
Photos: © Thomas Cubitt
© Derek Crawley
© Mike Brown
Notes to editors
For more quotes and details, or images of harvest mice and surveyors in action, please contact Afrika Priestley, Data & Research Officer: afrika@mammal.org.uk
More information about the survey can be found on the Mammal society website, including a field guide for surveying and recorded training webinar: mammal.org.uk/current-research/national-harvest-mouse-survey
Information about harvest mice: Harvest mouse — Mammal Society
The first ever National Harvest Mouse Day will be celebrated on October 19th 2025 - National Harvest Mouse Day | Awareness Days
The Mammal Society was founded in 1954 and has been leading on research into mammals, raising awareness of the issues they face, sharing scientific research and providing training and guidance for professional ecologists and conservation volunteers to ensure a bright future for native British mammals.
The public can get involved with the Mammal Society’s work by using the Mammal Mapper app and make their mammal spots valuable to scientists.
Harvest Mouse Habitat Suitability Map
Dark red: Ideal habitat conditions, very likely presence
Dark blue: Very unsuitable habitat, very low probability of presence