With large swathes of mature woodland, well-established hedgerows and numerous secluded stream valleys, the Wrekin Forest has many features guaranteed to pique the interest of one of our most enigmatic groups of mammals. The UK is home to eighteen bat species and, while not all are present on our patch, or always easy to identify, there is plenty of scope to witness their aerial antics over land and water — which in itself can help put a name to many a winged silhouette…
Long-lived oak and beech trees found in ancient places like The Wrekin Forest are especially valuable to bats. They contain plenty of standing dead wood, which rots from the inside and creates hollows and holes suitable for them to roost in. In bat terms, a ‘roost’ is essentially somewhere that provides shelter and protection. However, bats are extremely sensitive to changes in temperature and humidity and utilise many different sites (which are often communal) throughout the year. Consequently, locations with lots of trees will cater more effectively for their needs.
Insects are something else bats require in plentiful numbers. It’s been estimated that the Common Pipistrelle, Britain’s most common bat, can take up to 3000 small flies, midges and mosquitoes a night, which, together with beetles and moths, are the typical prey of many species. Sadly, our bats do not appear to be finding enough insects to eat or suitable sites in which to roost. The UK population declined markedly over the course of the Twentieth Century and, even in seemingly ideal places like the Wrekin Forest, numbers appear to be well below what experts would expect to find.
To catch their prey, bats make a high-pitched shouting sound inaudible to the human ear. Using the returning echo, they are able to build up a forensically detailed picture of what’s in front of them. Conveniently for us, each bat species has its own sonic fingerprint, so to speak, and by using a specialised detector it is possible to establish the individual frequencies and calls of any given species. However, what can you do if you don’t happen to have this relatively expensive piece of equipment about your person? While far from failsafe, the bats you’re likely to see flying around The Wrekin all have their own peculiar traits — so, even if you can’t identify them, you can at least have fun trying!
Regularly seen ‘hawking’ for insects (which are eaten on the wing) well below the tree tops, the fast and jerky flight of Common Pipistrelle is probably The Wrekin’s most recognisable bat spectacle. Males of the species are at their most active around roost sites during the breeding season (between July and early September) when they attempt to attract females by making songflights and social calls, which can be audible to humans. The Brown Long-eared bat is another species with a hovering, butterfly-like flight that inhabits coniferous and deciduous woodland. However, as well as taking prey in mid air, it can glean insects from tree bark and windows, and land on the ground — taking away larger food parcels to eat later from the comfort of a perch.
A Wrekin species with a very different modus operandi is the Noctule. Powerful and direct in flight, it is one of the UK’s largest bats and reminiscent, in size and form, of a narrow-winged Starling. Flying in the open, and often well above tree level, Noctules can roam up to 10km in search of insects, which are often pursued in a ‘stoop-like’ dive. Daubenton’s bat is another highly distinctive species capable of ranging over relatively large areas but has a close association with water (where it is often the most numerous species). Scan the Ercall Reservoirs at dusk and you may just be lucky enough to see one skimming the water, catching midges and scooping up caddisflies and mayflies with its feet. For Daubenton’s, the presence of water is a prime consideration in choosing roosting sites, which are often found in humid, subterranean locations (although tree holes are also used).
Common Pipistrelle (Pipistrellus pipistrellus): typically emerges around twenty minutes after sunset. Flight pattern is twisting and erratic, often centred around street lamps, buildings, trees and hedges. Females form ‘maternity colonies’ in summer, giving birth to single young, who can fly after a month and forage independently by six weeks. Echolocates at 46 kHz (call is a mildly repetitive ‘smack’).
Soprano Pipistrelle (Pipistrellus pygmaeus): very similar to the Common Pipistrelle, and only recognised as a separate species in the 1990s. Evidence suggests they’re more selective in terms of habitat, displaying a preference for wetland habitat, but also hunting on woodland edges and along hedgerows. Echolocates at 55 kHz (call is a mildly repetitive ‘smack’).
Noctule (Nyctalus noctula): one of the UK’s largest species — starling-sized with distinctive narrow wings. High-flying, powerful, direct flight. Often the first bat to enter the skies of an evening. Predominantly a tree dwelling, woodland species, roosting in rot holes and old woodpecker nests. Echolocates at 20-25kHz (call is a very slow ‘chip-chop’). Noctules are also capable of loud, metallic chirping and colonies can sometimes be heard several hundred metres away.
Daubenton’s Bat (Myotis daubentonii): steady, hovercraft-like flight, typically witnessed skimming low over water in search of aquatic insects. Echolocates at 45 kHz (call is a fast ‘tik-ke’).
Brown Long-eared Bat (Plecotus auritis): often flies very close to trees, in a slow, hovering fashion that includes regular steep dives and short glides. Often roosts in old woodpecker holes in woodlands. Its ears, which are curled-up or tucked way under the wing at rest, are nearly as long as its body. Echolocates at 45-50 kHz (call is a quiet but very fast ‘chip’, which has earned it the nickname of the ‘whispering bat’).
Whiskered Bat (Myotis mystacinus): small bat with shaggy fur that was only separated from Brandt’s Bat as a species in 1970. Emerges around half an hour after sunset, and notable for fast, fluttering flight with the occasional ‘swoop’. Frequently navigates woodland edges and hedgerows. Regularly favours crevices in older buildings as roost sites. Echolocates between 32-89 kHz but loudest at 45kHz (call is a dry ‘click’, similar to Daubenton’s bat but not as regular and often slower)
British bats have evolved to live in trees, so mature woodlands — which are typically abundant in insects — can offer plentiful feeding and roosting opportunities for them. Limekiln Wood, Short Wood and Black Hayes are all areas of The Wrekin Forest where bats have been recorded, while The Wrekin hilltop, with its insect-rich heather heathland, is another place worth investigating. Given their sensitivity to temperature and humidity, roost sites need to fulfil varying expectations, with warmer and cooler conditions required at various times; It’s not unusual for a single bat to use up to twenty sites throughout the year, which these long-lived creatures will often return to time and again. Sheltered trees receiving plenty of sunshine will provide warmer conditions, while smaller tree holes in dense woodland give a higher degree of insulation in cold weather. In summer, trees with plenty of damp rot holes will also help guard against dehydration, which can be a particular problem for bats.
• Older trees, especially Oak and Beech, with holes and cavities (at least 10mm in diameter) in large broad-leaved woodlands with a good shrub understorey. Age, size and damage all increase the probability of selection for roosting.
• Trees covered in dense climbing plants (eg. Ivy) that help to control microclimate.
• The presence of water features that support large numbers of insects.
At landscape level, species that hunt over a wide area (such as Noctule and Daubenton’s bats) often utilise green corridors to guide their way. Wide woodland rides and edges, unbroken hedgerows with trees, and stream valleys are all typical linear features used for navigation.
For detailed species and habitat information, and the law relating to bats, visit the Bat Conservation Trust