Mammals


Image above by Max Anderson
Hazel dormouse Muscardinus avellanarius - Vulnerable

Dormice have been lost from about half their former range in England: Devon is now a national stronghold. The decline continues - an analysis of data derived from the UK’s National Dormouse Monitoring Programme (NDMP) strongly suggests that dormice have suffered a 72% population crash between 1993 and 2014, equivalent to a mean annual rate of decline of 5.8%. They are small mammals of early to mid-successional woody growth, whether this occurs as scrub, in hedges or in woodlands. The population fall is thought to be due to habitat loss, especially the loss of dense scrubby growth, and a reduction in habitat quality, for example more woodlands becoming high forest with a closed canopy and more hedges becoming gappy. Landscape fragmentation is considered a further reason for decline since it leads to the loss of safe dispersal corridors. Changing climatic conditions adversely affecting hibernation, and increasing deer numbers removing undergrowth, may also be factors. Across the country, there is no clear regional pattern to this decline. The trend in Devon is unknown, but there is no reason to suspect that it bucks the national picture.

Map to show the Devon distribution of this species


Image above by Gilles San Martin


Bechstein's bat Myotis bechsteinii - Least concern nationally rare

This bat is in Britain largely restricted to central southern England: Beer Caves and Quarries in East Devon is a nationally important site for the species. Despite being strongly associated with broadleaved woodland, particularly semi-natural ancient woodland with a dense understorey, the species also forages along large hedgerows and wooded riparian corridors and can roost in individual trees found in such places. Maternity roosts are usually located in trees, most commonly in woodpecker holes and rot holes, but sometimes in other crevices. Hibernation sites include tunnels, caves, and probably also tree holes. Home ranges are also very small compared with most other British bats; several projects report core areas of less than 5.3ha and frequently even smaller. Bechstein’s Bat appears particularly vulnerable to habitat fragmentation: a study of a German population near a motorway found that no individuals flew over the road, and those that crossed used underpasses. Nationally, the bat’s range is probably stable, but no information is available on population trends – the specie is elusive and difficult to monitor. In addition to habitat loss and fragmentation, light pollution is a concern.

Map to show the Devon distribution of this species


Image above by Alexandre Roux

Grey long-eared bat Plecotus austriacus - Endangered and nationally rare

In the British Isles this bat is restricted to a few colonies in Sussex, Hampshire, the Isle of Wight, Dorset, Devon and Somerset. The main centre of distribution is in Dorset and east Devon. Nationally, its population is believed to be declining. The Grey Long-eared Bat is a cryptic species, very similar in morphology and flight pattern to the Brown Long-eared Bat Plecotus auritus. It is a specialist moth feeder. Although associated with open woodlands, this bat forages mainly in grassland habitats, including in meadows and along woodland edges, whereas the brown long-eared bat forages primarily within woodland. All maternity roosts in Great Britain are in the loft spaces of residential buildings. Hibernation sites for the species in this country are unknown, but elsewhere in Europe they use cellars, attics, underground galleries, mines, quarries, caves and rock crevices. As part of the Back from the Brink project, the Bat Conservation Trust is working with landowners to learn how to retain and enhance the habitats that Grey Long-eared Bats need. The project aims to connect the foraging habitat patches that remain and keep these grasslands in good health. The main threat is habitat loss and fragmentation (species rich grassland for foraging, hedgerows for connectivity). Other risks include barn conversions, urban development, artificial night lighting and road casualties. Trends in range and abundance of this species in Devon are unclear.

Map to show the Devon distribution of this species


Image above by John Walters
Greater horseshoe bat Rhinolophus ferrumequinum - Least concern nationally rare

Devon is a national stronghold for this large bat. The South Hams holds the largest population in the British Isles with over 1,500 adult bats (31% of the UK population) and is the only one with more than 1,000 adults. The district also contains the largest known maternity roost in the UK and, in a building, possibly in Europe. The area has been designated a European Special Area of Conservation (SAC) for Greater Horseshoes. These bats mainly feed on dung beetles and noctuid moths, foraging in pasture and parkland, and along woodland edges and tall hedgerows: they prefer landscapes with numerous large trees. The species is highly dependent on pasture grazed by livestock, particularly cattle. Maternity roosts form during the summer in buildings, whilst winter hibernation roosts are often in underground caves. Nationally, the population has grown consistently since detailed monitoring began in 1997, including dramatic increases in south Devon. It is predicted that further population and range increases will occur. The bat continues, however, to be at risk from loss of hibernation, mating and maternity roost sites, and from urbanisation and loss of grazed pasture and of hedges. It is also highly sensitive to light pollution. Working across Devon, the Devon Greater Horseshoe Bat Project, a partnership project hosted by the Devon Wildlife Trust, is working to secure the future of this species in the county, in particular working with farmers, landowners and local communities to improve habitat quality.

Map to show the Devon distribution of this species

Further sources of information:

The Mammal Society

Devon Mammal Group

Devon Bat Group

Bat Conservation Trust