Devon Mammal Group

Lesser Horseshoe Bat

Lesser Horseshoe bat (image: Jessicajil www.flickr.com)

Common Names
Lesser Horseshoe Bat

Scientific name and classification
Family: Rhinolophidae
Genus: Rhinolophus
Species: R.hipposideros

The generic name Rhinolophus derives from the Greek for 'nose crest', and the specific name hipposideros derives from the Greek for 'horse-iron' or horseshoe. This name refers to the complex nose-leaf, which is thought to act as an 'acoustic lens', focusing echolocation pulses that are emitted from the nose

Conservation/Protected Status
The lesser horseshoe bat is protected or listed under:

  • Annex II of The Bonn Convention
  • Annex II of the Bern Convention
  • Annexes II and IV of the EC Habitats and Species Directive

In the UK...

  • Schedule 5 of the Wildlife and Countryside Act 1981
  • Schedule 2 0f the Conservation of Habitats and Species Regulations 2010 (known as "European Protected Species")

The lesser horseshoe has a Species Action Plan in both the Dartmoor and Teignbridge Biodiversity Action Plans (BAPs).

  • The worldwide IUCN status (2001) for lesser horseshoe bats is Vulnerable.
  • The British pre-breeding population was estimated at 14,000 in 1995 (7000 in England, 7000 in Wales ) (Harris et al., 1995).  More recent data indicate that the lesser horseshoe population may be increasing; colony counts indicate that the UK population may now be 24,000 (Battersby, 2005).
  • Twelve lesser horseshoe sites are designated Sites of Special Scientific Interest (SSSIs). 70 further sites supporting this species occur within existing SSSIs.

Current and local status
The population is rare and localised populations, restricted to Wales, the West Midlands and south west England.  South Devon has some of the highest population densities in the UK.

Current factors affecting loss or decline
Decline has been attributed to a number of factors including:

  • Loss or disturbance and destruction of roosts
  • Remedial timber treatment
  • Increased use of insecticides and a reduction in prey availability.
  • Loss of suitable foraging habitat
  • Lesser Horseshoes  used to benefit from abandoned mine workings, but sealing of old mines is likely to have reduced the population and range.
  • Lesser horseshoe bats are particularly sensitive to disturbance.

General Description
The lesser horseshoe is easily identified by a horseshoe-shaped flap of skin surrounding the nostrils.  They are so-named from the horseshoe shaped nose 'leaf', used as part of the bat's echolocation system. The ears are leaf-shaped and have a sharply pointed tip.

The fur is long and fluffy. Dorsal fur is pale greyish-brown; ventral fur is pale grey whilst juveniles fur is darker grey.

It can be distinguished from the greater horseshoe bat by size.  Average body dimensions are;

Head and body length 35mm - 45mm
Forearm length 35mm - 42mm
Wingspan 200mm - 250mm
Weight 5g - 9g

Surveying the Lesser Horseshoe Bat
Only people who are trained and hold licences are allowed to handle bats or conduct survey work which may lead to roost disturbance.

Horseshoe bats have a specialised echolocation that helps them fly through cluttered environments; lesser horseshoe bats have an almost constant frequency call, about 110kHz.  This is higher frequency than the other British and Irish bats, and the sound on a heterodyne bat detector is quite distinctive. 

Unlike many other bat species, field signs of the lesser horseshoe are very characteristic, making it simpler to identify the presence of a roost.  This includes droppings which are frequently composed of double/triple ovoid shapes, which build up into significant accumulations at maternity roosts  (Vincent Wildlife Trust, 2008).

Habitat
Lesser horseshoe bats feed amongst vegetation in sheltered lowland valleys. They rarely fly more than five metres above the ground, frequently circling over favoured areas and often 'gleaning' their prey from stones and branches. Large prey is often taken back to a temporary night roost or sometimes dealt with whilst the bat is hanging in trees. Feeding remains are found in such places, particularly in porches and the entrance to tunnels feed in sheltered valleys, and foothills, amongst mixed woodland, and along hedgerows and tree lines.

Summer roosts: Lesser horseshoe bats were originally cave dwellers, but summer colonies are now usually found in the roofs of larger rural houses and stable blocks offering a range of roof spaces and a nearby cellar, cave or tunnel where the bats can go torpid in inclement weather. They prefer access through an opening that allows uninterrupted flight to the roof apex, but they are capable of using more inconspicuous gaps. The colony may shift between attics, cellars and chimneys throughout the summer, depending on the weather. The whole colony may form a dense cluster, especially in cooler weather during lactation, but if the roost gets very hot individuals hang spaced slightly apart. They can find new sites very quickly e.g. a rural building with a broken window is likely to be colonised

Winter roosts: Lesser horseshoe bats hibernate from September or October until April and frequently into May, using caves, mines, tunnels and cellars. Lesser horseshoe bats are often active in the hibernaculum in autumn and spring, especially towards dusk in warm weather, when feeding is more likely to be successful. They appear to select places with similar temperatures to those sought by greater horseshoe bats, preferring temperatures of up to 11ºC and with a high humidity. Males tend to arrive earlier than females and are often more numerous. Many sites only have one or a few bats hibernating in them and it is rare to find large numbers in a site. Even when aggregated, lesser horseshoe bats do not cluster but hang a little apart from their neighbours, usually exposed, but sometimes in open crevices. They may be found at any height within an underground site, and they venture much further into underground sites than other bats.

Life History Traits
The diet of lesser horseshoe bats mainly consists of Diptera, particularly the suborder Nematocera. Nematocerans are generally crepuscular and the males often swarm (Vaughan, 1997).

Mating occurs during the autumn, usually in October. A single young is born between June and July in mixed sex maternity colonies (Ransome, 1991b).  Young become independent at six-seven weeks of age, and most young are sexually mature in their second autumn.

The maximum age recorded in Europe is 21 years but on average lesser horseshoe bats only live four years (Schober & Grimmberger, 1989).

Behaviour

Emerges late after sunset and returns to the roost close to sunrise (Ransome, 1991b). Median emergence time is 31 minutes after sunset (Jones & Rydell, 1994); they are sensitive to light levels and will 'light sample' at the entrance of the roost until it is dark enough to emerge.  Hunting flight is slower and initially follows a regular path before the bat moves into vegetation.

Current Research
The species is selected for proposed international collaboration on population monitoring under the European Bat Agreement.  Coordinated monitoring of summer roosts in Wales and England has been taking place for several years.  Monitoring of hibernation sites has been carried out over the past year in order to develop a long term monitoring programme.

Forest Design Plans, Countryside Stewardship Schemes, ESAs and other relevant agri-environment and forestry schemes to land in the vicinity of important roost sites, with the aim of enhancing and extending habitat used by bats.

Protected sites have been selected to include large populations of lesser horseshoe bats, covering the geographical range of the species. In order to maintain populations, both maternity and hibernation sites must be protected, and so sites have been selected, where possible, as composites of maternity and hibernation sites considered to belong to a single population or group of closely-associated populations.

Consideration is given to key maternity roost sites and the surrounding habitat when developing structure plans and assessing planning applications, particularly those for redundant buildings. Surveys and provision of alternative roost sites is required to mitigate any loss through development.

Lesser horseshoe bats have been the focus of recent research by Bristol University on the impacts of lighting on bats; a study published in 2009 demonstrated that the bats avoid hedgerows illuminated by streetlights  (Stone, E.L., Jones, G., & Harris, S. 2009).

Links

The Devon Bat Group: http://www.dbg.me.uk/

The Bat Conservation Trust: http://www.bats.org.uk/pages/uk_bats.html

Vincent Wildlife Trust: http://www.vwt.org.uk/species/horseshoe.php

Species Action Plan under UK Bioodiversity Action Plan: http://www.ukbap.org.uk/UKPlans.aspx?ID=551