Terrestrial mammals

Devon’s terrestrial mammals are some of our most iconic species.  

However, they’re under pressure from things like loss of habitat, litter, pesticides, lighting and climate change. 

Nationally, hedgehogs have declined by as much as 73% in some rural areas. 

What we need to do and where
Hedgehog in autumn leaves

Hedgehog – Ben.Andrew (rspb-images.com)

Brown pine marten on a branch, with a fern below it. Looking intensely into the camera

Pine marten – Ben.Andrew (rspb-images.com)

1. About

Devon supports all native terrestrial mammals other than the Irish (mountain) hare, yellow-necked mouse, red squirrel and wildcat. Devon also has both UK breeds of feral horse (Dartmoor and Exmoor ponies) and a herd of feral goats.  Terrestrial mammals living on watercourses are discussed on the freshwater mammals page.

Terrestrial mammals live in all habitats across Devon, including urban areas. Unlike other species many terrestrial mammals such as badgers, hedgehog and foxes are easy to identify and well known. Other common species include mice, voles, shrews, deer, stoats, weasels, polecats, and (following their re-introduction in 2024) pine martens. Non- native mammals include rabbits as well as deer and grey squirrels which are both discussed on the Invasives page.

Most small mammals are under-recorded, so not much is known about their population size and distribution.  Stoats and weasels are also under-recorded. Polecats are known to be breeding in the wild in Devon following unofficial releases. Species under threat and identified as Devon Special Species are listed below.

Devon Wildlife Trust and partners are currently working on the South West Wildcat Project which is investigating whether it is possible and appropriate to re-introduce wild cats to Devon and other parts of the region. See links in Find out more.

Key pressures and opportunities

camera

Loss, deterioration and fragmentation of habitats

The loss, deterioration, and fragmentation of habitats is a major pressure on terrestrial mammal populations.  New developments and roads reduce the amount of habitat available, and cut populations off from each other, reducing genetic diversity.  In urban areas, car parking, decking, over-tidy gardens, and impermeable fences reduces the area available for foraging, and destroys hedgehog hibernation habitats.

The change from pastoral farming to arable crops, the removal of hedgerows to increase field sizes, and the loss of field margins, has reduced the habitat available for hedgehogs in rural areas.  Changes to hedgerow management (flailing instead of hedge-laying) leads to gaps at the base, making them less suitable for foraging and nesting, and also means that they can become patchy and can no longer function as a link between woodlands.  Dormice use the hedge network to move between woodlands, so loss of hedgerows isolates woodlands.  Once dormice have been lost from an isolated woodland, they are unlikely to return. 

The decline in traditional management techniques such as coppicing has meant that the woodland canopy becomes dense, shading out the understorey.  The loss of the shrub layer reduces food availability for dormice.  High deer numbers can also affect woodland regeneration by browsing the shrub layer, including preventing the regrowth of coppice stools.

Overgrazing can be a problem for harvest mice, as it can prevent grass tussocks from developing or remove the vegetation cover between tussocks. 

camera

Pesticides and insect decline

The use of slug pellets and pesticides in gardens and the widespread use of chemicals during intensive farming are known to poison hedgehogs and reduce the amount of invertebrate food available.  Harvest mice are also known to be very sensitive to pesticides.  Rodenticides and microplastics have been found in hedgehogs during autopsies and are known to be harmful to other small mammals. 

A decline in invertebrate populations means that animals must travel further to find food; this can affect breeding success and can make it harder for dormice and hedgehogs to gain enough weight before hibernation.  Invertebrate numbers are affected by habitat loss and climate change, as well as by the use of pesticides.

camera

Litter

A Keep Britain Tidy (KBT) study estimates that 3 million small animals are killed by roadside litter every year, against a backdrop of 2 million pieces of litter dropped every day in the UK. This represents an unnecessary, additional ongoing challenge for the health of our wildlife, habitats, and biodiversity.   

This 2016-17 Norfolk-based study sampled 2,174 bottles and from predominantly roadside locations and identified that 8% of littered glass bottles, and 5% of cans contained the remains of small animals (including shrews, voles, mice (including harvest mice) and insects(including beetles, woodlice, millipedes, slugs and snails).  

Despite the proposed introduction of a ‘Deposit Return Scheme’ for single use drinks containers in 2027, the English scheme will exclude glass bottles. Overall, the study identified that there may be local effects on small animal populations from litter related deaths, particularly in areas with low species populations. 

Glass bottles in East Devon have been found to contain the remains of hazel dormice. Hedgehogs can get caught up in litter such as yoghurt pots, tins and other plastics.  

Promoting litter picking to protect wildlife should be a relatively quick win and links directly to our wellbeing by enabling us to connect with nature and feel empowered by taking critical direct action.  Over 80% of people say that seeing litter on the streets makes then angry. There are also opportunities to highlight sensitive, designated sites and irreplaceable habitats for targeted litter control measures as part of routine operations. Devon County Council’s recent ‘Litter kills wildlife’ campaign in support of the Great British Spring Clean proved very popular with the public.  

camera

Road traffic and other dangers

Road traffic is the main threat to pine martens in Devon and is also a threat to other mammals such as deer, badgers, foxes and hedgehogs. It has been estimated that 167,000–335,000 hedgehogs (10-20% of the population) are killed on Great Britain’s roads each year. Roads can also act as barriers to movement and disrupt dispersal routes.

Garden machinery, ponds, and bonfires can kill or injure animals, and site clearances for development and building works can also cause problems. Hedgehogs will hibernate under bonfire heaps, so these should always be turned over before being burnt.  Robotic lawnmowers do not always detect hedgehogs, so they should not be used at night, and areas of rank vegetation should be checked before strimming. Steep-sided ponds should have a ramp to allow hedgehogs to escape.  Inappropriate food, such as bread and milk, can be lethal. Feeding can also have unintended negative consequences such as the spread of infectious and non-infectious disease, aggression between hedgehogs, and increased predation.

Pine martens can potentially be caught in traps set for grey squirrels, rats, and other mustelids.

camera

Climate change

Climate change affects mammals in many different ways. For example, extreme weather such as drought and heavy rain can reduce the amount of plants and invertebrates available as food. With less food, mammals may fail to breed and are less likely to survive in winter, particularly small mammals such as harvest mice. Wet weather and warmer springs and winters can also disrupt hibernation and breeding patterns and lead to higher mortality.  

camera

Knowledge

Little is known about hedgehogs’ distribution in rural areas as the majority of records come from gardens, while harvest mice are also under-recorded.  Devon is a stronghold for dormice, but it is hard to confirm their presence in habitats such as scrub, where there is no hazel.  It is also important to know how pine martens are dispersing across Devon.  New survey methods, such as footprint tunnels and trail cameras, will be very important, especially as these can be used by citizen science projects.

camera

Community action

Hedgehog Street (https://www.hedgehogstreet.org/) helps people create hedgehog highways by making holes in fences to connect hedgehog-friendly gardens.

Make a mammal friendly garden – gardens are important habitats for many mammals and there are plenty of things that can be done to make them mammal friendly https://mammal.org.uk/blog/wildlife-friendly-gardening

Mammal Web (https://www.mammalweb.org/en/) is a citizen science project where people can help to identify mammals on camera trap footage

2. What we need to do and where

Priority

Increase the abundance and distribution of terrestrial mammals across Devon, particularly those identified as Devon Special Species. 

See Find out more for links to more detailed information on this group including management advice and records. 

Devon Special Species

A hedgehog is pictured side on, standing on short green grass. The hedgehog is facing to the left with its furry head, neck and underbelly visible, as well as the spines along its back which are a darker brown than that of its fur. The snout and nose are also dark brown.

Hedgehog

Erinaceus europaeus
Read more

Habitat  

Hedgehogs are unmistakeable as they’re the UK’s only spiny mammal. They’re found in a wide range of densely-vegetated habitats such as the edges of broadleaved woodland, hedgerows, gardens and urban greenspaces.  

Hedgehogs are generally solitary and are more active at night or in the early morning. They can travel 1-2 kms to feed on invertebrates such as beetles, worms, caterpillars, millipedes, leatherjackets and slugs. They also eat eggs and chicks, baby rodents, frogs, dead animals and fallen fruit. 

Hedgehogs have one litter of hoglets a year, in June or July. They hibernate from November to March or April (depending on the weather) in a nest made of leaves that’s hidden away under a bush, pile of dead wood (including bonfire sites) or in an abandoned burrow.  Their main predators are badgers, and sometimes foxes. 

Population 

Since 1995, the population of hedgehogs in rural areas is thought to have declined by  73%. Hedgehogs in gardens and greenspaces are thought to be doing better, although they’re still in decline.  They are listed as threatened and are a UK priority species. 

Hedgehogs are particularly affected by loss and fragmentation of habitat. Flailing causes hedges to develop gappy bases that provide less cover. Many hedgehogs are also killed crossing roads that separate their habitat. Fewer invertebrates also means they have less food.   

Hedgehogs are found across Devon, other than the high ground of Dartmoor and Exmoor. They could be present in any suitable habitat.    

As they’re largely active at night hedgehogs are not always seen. A good way to know if they’re present is to identify their tracks or droppings. Check the NBN atlas for records or contact DBRC (see links in Find out more below). 

Actions

Manage and create a network of connected woodlands, bushy hedges, scrub and trees in rural and urban areas with abundant invertebrates (slugs, worms, beetles, caterpillars) and fruit.   

Ensure that all fences have a gap big enough for hedgehogs and other small mammals to pass through. 

See other actions below relating to litter, pesticides, road crossings etc  

Where to focus action

High Opportunity Areas: All woody habitats. See Mapping.

However actions are also needed across Devon in parks, gardens and hedge corridors.

Two hazel dormice are curled up within a nest of dry leaves that someone is holding up. The two dormice are side by side with their heads towards the top of the photo and their bums at the bottom, both facing to the right. They are golden yellow-brown on the back, head and sides and white on the belly, with furry darker grey brown tails that wrap around the bodies that are curled in on themselves. The dormice have pink hairless noses and four feet that are scrunched in on themselves as they sleep/hibernate with their eyes closed.

Hazel dormouse

Read more

Habitat  

Hazel dormice live in the branches of trees and shrubs and, except for when they hibernate, rarely touch the ground. They can be found in a wide range of habitats that have good woody connectivity and lots of food. These include broadleaved woodland, hedges, heathland mosaics and scrubby grassland such as the culm, rhos pastures and coastal grasslands. They’ve also been seen in conifer woodlands, bramble patches and using bird feeders in gardens.     

Hedges provide critical connectivity, allowing dormice to disperse into new habitats.  

Hazel dormice are nocturnal. They feed on flowers, fruits, seeds, nuts (especially hazelnuts) and insects such as caterpillars and aphids. Important foodplants include hazel, oak, honeysuckle, bramble, willow, rowan and birch.  

Dormice have one or two litters a year, usually between May and September. In summer they use plants such as honeysuckle and grasses to weave nests which they hide in holes in trees, old bird nests, dense scrub and hedges. They generally don’t travel more than 70m from their nest. 

Dormice build their hibernation nests at ground level, tucked among tree roots or under dead leaves, logs or moss.    

Population 

There has been a long-term decline in both the numbers and range of dormice.  The main reason for this is thought to be habitat loss and deterioration. As a result, their UK conservation status assessment is unfavourable.  Dormice are classed as nationally threatened, are a UK priority species and are legally protected.  

Devon is a national stronghold for dormice and they can be found in suitable habitat throughout the county. There are few records in parts of rural north, west and south Devon but this may be due to lack of survey (as most records come from surveys for developments) rather than lack of dormice.   

As dormice are nocturnal they’re not easy to spot. One way is to look for hazelnuts that have  a neat, smooth hole, caused by the dormice’s precise nibbling.  Check the NBN atlas for records or contact DBRC (see links in Find out more below). 

Actions

Manage and create a network of connected woodlands, bushy hedges, dense scrub and trees in rural and urban areas with abundant hazel, honeysuckle, flowers and insects.  See habitat pages for more details.

Also see actions below relating to pesticides, litter, road crossings etc.

Survey and research 

  • Develop a more strategic approach to monitoring dormice populations across Devon. Use new survey methods such as e-DNA, radio tracking, thermal cameras and footprint tunnels.
  • Extend the National Dormouse Monitoring Programme in Devon.
  • Share monitoring of habitat created as mitigation for new development with Devon Biodiversity Records Centre and People’s Trust for Endangered Species to ensure better understanding of how to compensate for loss of dormouse habitat. 

Where to focus action

High Opportunity Areas: All woody habitats. See Mapping.

However actions are also needed across Devon in parks, gardens, scrubby habitats and hedge corridors.

Brown pine marten on a branch, with a fern below it. Looking intensely into the camera

Pine marten

Read more

Habitat

Pine martens are members of the weasel family and are about the size of a small cat. They live in woodlands where they are good tree climbers. They need areas with safe (they are predated by foxes), sheltered places for resting and breeding known as dens. These are usually above ground level and can include tree cavities and hollow trees, abandoned squirrel dreys (nests) and old birds’ nests.

Pine marten’s are largely carnivores eating voles as well as mice, grey squirrels, birds and insects. Fruits are an important part of their diet in the autumn. It isn’t yet known whether pine martens can suppress populations of grey squirrels which are a non-native invasive species.

They are mainly nocturnal, but sometimes come out during the day in the summer.  They don’t hibernate but are less active during the winter.

Pine martens are solitary (other than females with young) and have territories of between 1km2 and 10km2. They are generally disperse up to 50kms but have been known to travel up to 100kms.

Population

Pine martens were very common and widespread in Britain after the last Ice Age (around 10,000 years ago). The population declined drastically from the late 1800s due to loss of woodlands and hunting/persecution and they became extinct in most of England and Wales.  Now, they are one of Britain’s rarest mammals and are mainly found in the Scottish Highlands, North Wales, and northern England. They are being reintroduced to several areas.

Pine martens are thought to have become extinct in Devon, Somerset, and Cornwall between 1870-1880. They are now being reintroduced to Dartmoor and Exmoor by the Two Moors Pine Marten Project (https://twomoorspinemartens.org/). Animals were released on Dartmoor in autumn 2024. Pine martens have also been recorded in north Devon and Exmoor but the origin of these isn’t known.

Actions

Manage, expand and connect broadleaved woodlands with healthy populations of small mammals and insects, lots of fruit in the autumn and veteran trees providing habitat for dens. See Broadleaved woodlands.

Continue the Two Moors Pine Marten project, including monitoring and liaison with local communities.

Report sightings of pine martens to Devon Wildlife Trust.

See actions below relating to road crossings, litter, pesticides etc.

Where to focus action

High Opportunity Areas: Ancient and broadleaved woodlands (existing) and woody expansion areas. The intitial focus of the re-introductions is Dartmoor and Exmoor but if successful pine martens are likely to spread across Devon.

A harvest mouse looking upwards, as if to climb a small branch

Harvest mice

Micromys minutus
Read more

Habitat  

Harvest mice are Europe’s smallest rodent, weighing only 6-9g. They’re found anywhere that has abundant food and tall, tussocky grasses or reeds such as hedgerow corridors, tussocky grasslands, road verges, reedbeds, ditches and saltmarshes. They’re good climbers and live mostly in the stalk zone where they feed on seeds, berries and insects. They are now rarely found in cereal crops as the gaps between stems are usually too wide for the mice to build their nests.    

Grass tussocks need to be at least a year old before they’re strong enough to support nests. Species which form tussocks include cock’s foot, tufted hair-grass, reed canary-grass, reed sweet-grass and purple moor-grass. Harvest mice build their nests by splitting and weaving the leaves of grasses or reeds. The nests stay attached to the stem, generally over half way up. 

Harvest mice usually have two to three litters a year, between May and October although they can breed into December. They don’t hibernate.  

Population 

Due to a lack of national survey, little is known about the national population. The Mammal Society believes that numbers have declined nationally due to loss of habitat and they are a UK priority species.  

The Devon Harvest Mouse Project is working with volunteers to find out more about the county’s population. Results to date show that they seem to be widespread across Devon but in low numbers and potentially declining.   

Actions

Manage (through light grazing or rotational cutting) and create a network of connected habitats with tussocky grasses or reeds for harvest mice nests and with abundant insects, berries and seeds for food.    

Where to focus action

High Opportunity Areas include all mapped areas in the following groups: Wildlife-rich grasslands, Heath, mire and species-rich rush pasture mosaics, Coast (saltmarsh, reedbeds, coastal wildbelt).

However actions are needed across the county in all suitable habitats such as hedge corridors, road verges, railway corridors and other greenspaces.

Actions for all

Provide safe road crossings, especially for pine martens, dormice and hedgehogs, following latest national guidance. 

Reduce the use of, and target applications of, pesticides. 

Reduce litter: 

  • Further develop and promote Devon County Council’s ‘Litter kills wildlife’ campaign in support of the Great British Spring Clean.  
  • Everyone to reduce littering and to litter pick as a normal part of day to day life. 
  • Local Authorities to target routine litter operations to wildlife-rich sites, guided by the LNRS mapping. 

Check for wildlife before habitat management / removal. Check for dormice, hedgehogs, harvest mice (and any other mammals) before carrying out work such as strimming, tree works and lighting bonfires (it is a criminal offence to kill or disturb nesting dormice). Ideally carry out work in and around October, after breeding but before hibernation.  

Research, survey, collaboration and awareness  

  • Share sightings of dormice, hedgehogs, pine martens and harvest mice with Devon Biodiversity Records Centre.
  • Carry out further research into effective road crossings.
  • Raise awareness among all land managers, such as farmers, foresters, highways authorities gardeners and landscape contractors.   
  • Support the Devon Harvest Mouse Project to continue their work with land managers and volunteers. 

3. Inspiration

This section will be finalised following public consultation. Please share any case studies and places to visit.

Case studies

Devon Harvest Mouse Project was set up in 2016 by the Devon Mammals Group to research harvest mice in Devon. The project works with land management-based conservation projects such as Moor Meadows and the Avon Valley Project to raise awareness of harvest mice and run survey training.  

A harvest mouse looking upwards, as if to climb a small branch

Could include pine marten reintroduction / Connecting People and Landscapes / Litter campaign 

The Two Moors Pine Marten Pproject (https://twomoorspinemartens.org/) aims to reintroduce pine martens to Dartmoor and Exmoor helping to restore natural balance to Devon’s woodlands. The first pine martens were released on Dartmoor in autumn 2024, with releases on Exmoor planned for autumn 2025.

Where to visit

Always follow the Countryside Code and keep to footpaths and sites that are managed for public access.

Good places to see terrestrial mammals are:  

For information on visiting these and other sites that are open to the public please see the Explore Devon website.

4. Find out more

 This section will be tidied up and finalised following public consultation. Please share any links.

General and species records

Devon Mammal Group is open to anyone with an interest in mammals. They organise talks and events and lead the Devon Harvest Mouse Project.  

The Mammal Society website has information on all species, including how to identify them or their signs (such as tracks and droppings).  

IUCN approved Red List for Britain’s Mammals. 

The JNCC Conservation Designations for UK Taxa 2023 contains data from the 

JNCC, NE, NR, NatureScot and NIEA © Copyright and database right 2023.  

JNCC UK BAP List of UK Priority Species 2007  

The NBN Atlas has species records and a search function that pulls up records for a specific area. Health warning: The Atlas shows records submitted and not the actual distribution of species. Therefore absence on the map does not mean absence. Some of the records are also quite old and the species may no longer be present.   

Devon Biodiversity Records Centre (DBRC) collects, manages and makes available records of wildlife. Note: they may charge depending on the reason for the request. 

iNaturalistUK helps you identify wildlife and share records. 

The Wildlife Trusts have worked with National Highways to improve connectivity for wildlife – see Network for Nature | The Wildlife Trusts

Hedgehogs

The British Hedgehog Preservation Society (BHPS) funds research and raises awareness of hedgehogs and their needs. 

The People’s Trust for Endangered Species (PTES) works with the British Hedgehog Preservation Society to coordinate hedgehog conservation work across the UK, including national surveys. There’s lots of useful information on their website.  

Hedgehog Street, encourages people to make gardens more hedgehog-friendly. 

Devon Wildlife Trust led a hedgehog survey in 2011. The details are available from DBRC. 

Dormice

The People’s Trust for Endangered Species (PTES) coordinates dormouse conservation work across the UK, including national surveys. There’s lots of useful information on their website.    

The Devon Mammal Group funded a 2013 report on dormice in gardens.  

Managing woodlands and hedges for dormice 

PTES guidance on managing woodlands for dormice (includes links to the Dormouse Conservation Handbook and PTES leaflet). 

Devon Hedge Group has a leaflet on the importance of hedges as habitat for dormice. 

Dormouse surveys

PTES runs the National Dormouse Monitoring Programme (NDMP), which monitors the long-term dormouse population trend. Volunteers set up and monitor sites that have a minimum of 50 nest boxes. There are 103 NDMP sites in Devon. 82 have been monitored at some point between 2012 and 2022 and 53 of these were still active in 2022.    

PTES also report on The State of Britain’s Dormice. 

The National Dormouse Footprint Tunnel Survey is a pilot project run by PTES and Natural England to detect the presence of dormice in hedgerows. The project also assesses the condition of the hedgerow using the Great British Hedgerow Survey.  

Devon-based K9 commando is piloting the use of sniffer dogs to survey for dormice.  

PTES ran The Great Nut Hunt in 1993 and 2001. The first survey identified 81 sites in Devon with dormice. It’s a good way for members of the public to survey for dormice, as it does not require a licence. DBRC has the records from these surveys  

Nest tube surveys can be used in areas where nut hunts are unlikely to be effective. A licence is required to check nest tubes if dormice are likely to be present.  

The Woodland Trust and National Trust are carrying out conservation for dormice in Fingle Woods. 

Devon Wildlife Trust’s Avon Valley Project is helping increase the population of dormice in the area. 

The Blackdown Hills Natural Futures Project (2015-2017) led to 30+ new volunteers surveying 300 new dormice nest boxes in five new monitoring sites 

University of Exeter dormice research

Ellie Scopes: Are hazel dormice Muscardinus avellanarius Endangered?  
Charlotte Armitage: Conservation of the hazel dormouse on the edge of the species’ range. 
Cecily Goodwin: How woodland management can help save dormice.  
Leo Gubert: Hibernation ecology and population biology of the hazel dormouse. 
Cheryl Mills: Non-invasive methods for surveying dormice. 
All these projects were short-term, generally lasting two or three years. The National Dormouse Monitoring Programme is the only long-term project, running since the 1990s.  

Pine marten

Read more about Devon’s Two Moors Pine Marten Project

More information about pine martens can be found on the Vincent Wildlife Trust website.

Harvest mice

The Devon Mammal Group runs a harvest mouse project that aims to find out how the species is doing in Devon and where they can be found. 

The Mammal Society runs the National Harvest Mouse Survey. They’re looking for volunteers who can get outside and look for harvest mouse nests. 

Wild cats

South West Wildcat Project | Devon Wildlife Trust

Search this site:

clear