---
title: "Hazel dormouse winter deaths in Britain fell to 31%, among the lowest rates since the early 1990s"
url: https://badiyaa.com/hazel-dormouse-britain-winter-survival/
published: 2026-11-12T13:32:00+00:00
modified: 2026-11-12T13:32:00+00:00
section: Pets & Animals
publisher: Badiyaa
---

# Hazel dormouse winter deaths in Britain fell to 31%, among the lowest rates since the early 1990s

Only 31% of Britain's monitored hazel dormice died over the 2024-25 winter, one of the best survival rates since the early 1990s, PTES says.

Only 31% of Britain’s monitored hazel dormice died during the winter of 2024 to 2025, one of the best survival rates recorded since the early 1990s. For a species that usually loses between 40% and 70% of its numbers while hibernating, that is a rare piece of good news.

The figure comes from the People’s Trust for Endangered Species (PTES), the conservation charity that runs the National Dormouse Monitoring Programme, in which volunteers check thousands of wooden nest boxes in woods across the country. The charity’s verdict on 2025, published in April, was short: “It appears that it was” a good year.

## Why a mild winter and a hot summer helped

The hazel dormouse spends a startling share of its life asleep. It hibernates from around October until late April or May, and on cold, wet summer days it drops into torpor to save energy, according to its [Wikipedia entry](https://en.wikipedia.org/wiki/Hazel_dormouse). Every hibernation is a gamble: the animal must fatten up from about 17 to 20 grams to as much as 30 to 40 grams to last until spring.

The PTES analysis links 2025’s success to weather. The winter of 2024 to 2025 was milder than average, if patchy. Spring 2025 was provisionally the warmest and sunniest on record for the UK, and summer 2025 was the warmest UK summer on record. Those dry, warm months may have produced a bumper crop of fruit and nuts on native trees and shrubs, the charity suggests.

Survival matters because of timing. Females that give birth in May or June can raise a second litter the same year, and their early young can breed before winter. PTES found a link between good winter survival and more spring litters, which can mean more adult dormice counted in autumn.

## A March surprise in the nest boxes

The early months of 2026 brought another hopeful sign. Since 1990, monitors have found just 252 dormice in 45,730 nest boxes checked in March, about one animal per 180 boxes. This year one site reported 11 dormice in 75 boxes in March, and six were found in a Nottinghamshire wood.

Run the numbers and that one site turned up a dormouse in roughly every seventh box, about 26 times the long-term March rate. PTES itself asks whether dormice may be adapting to a changing climate, but a single site is not a national trend, and the charity notes that a wet early 2026 could still have set the population back.

## The bigger picture

The good year sits against a long decline. PTES says the species’ national numbers have fallen by more than 70% since 2000, driven by habitat loss, poorer hedgerows and climate change. Wikipedia cites an estimated 72% fall between 1993 and 2014, and the hazel dormouse is rated Vulnerable in Great Britain even though it is listed as Least Concern across its wider European range.

Reintroductions are part of the fightback. Here is how the recovery work looks in numbers:

- **1993:** the PTES reintroduction programme begins.

- **More than 1,100:** dormice released into British woods since then.

- **21:** dormice released at Bradgate Park in Leicestershire in 2025.

- **46:** dormouse nests recorded there by volunteers in autumn 2025, along with several litters.

- **More than 40:** further dormice released at Bradgate Park in 2026, strengthening Leicestershire’s only known population.

“We’re thrilled that more dormice will be joining our existing population this year,” said James Dymond, director of the Bradgate Park Trust, in the charity’s announcement.

## How to tell a dormouse has been nearby

Dormice are nocturnal and rarely seen, but they leave a calling card. A hazelnut opened by a dormouse has a neat round hole with tooth marks running around the cut edge and angled marks on the outer shell. Squirrels and jays split nuts or leave jagged holes instead.

Britain’s wildlife has had other small wins this year, from the [young swan netted to safety on England’s A1](https://badiyaa.com/young-swan-a1-rescue-waterfowl-sanctuary-viral/) to the [cygnet freed from a fishing hook at St Ives](https://badiyaa.com/st-ives-swan-fishing-hook-rescue-video/). More stories live in Badiyaa’s [Pets & Animals section](https://badiyaa.com/category/pets-animals/).

The next test comes in spring 2027, when monitors open the boxes again to count how many dormice made it through this winter.

## Further reading

- [Wikipedia: Hazel dormouse](https://en.wikipedia.org/wiki/Hazel_dormouse)

*Image: Frank Vassen, CC BY 2.0 via Wikimedia Commons*

*This article was produced with AI assistance and reviewed by our Editorial Desk. [How we work](https://badiyaa.com/editorial-policy/).*