May is the start of the bat activity season, so we wanted to look into one of the most frequently encountered species: brown long-eared bats Plecotus auritus. As the second most common bat in Britain with a population of 245,000, they have unique characteristics and has been affected by the changing land use over the years.
Let’s delve deeper into this magnificent flying mammal.
All About Brown Long-Eared Bats
The brown long-eared bat is a medium-sized bat with greyish-brown fur with a pale underside and characteristically big ears. Their ears are nearly as long as its body which can grow up to 8cm in length and their wingspan can grow between 20-30cm. When resting, brown long-eared bats actually curl their ears back or tuck them under their wings.
Generally, their flight is relatively slow and manoeuvrable, plus they have the ability to hover. Often call ‘whispering bats’, they produce quiet calls between 25 – 50kHz which can only be heard by bat detectors that are closer than 5m. Their overall weight falls into the bracket of 6-12kg, and their average lifespan is 4-5 years.
Habitat & Diet
Found across the UK, these bats roost in a variety of habitats but they are typically found in light woodland, more specifically holes in trees. However, they are also commonly found in old buildings which is why our bat surveys for buildings are popular this time of year.
Their diet consists of insects and invertebrates such as flies, caddis flies, moths, beetles, and earwigs. They catch these by gliding slowly and diving low to forage for them on the ground. Although they eat this prey during flight, they also hunt bigger prey which they then consume by perching upside-down.
Their characteristically large ears help immensely when it comes to hunting. With sensitive low frequency hearing and echolocation, they have a great sense of direction and are able to locate prey from their movements. Sometimes they use vision, but their ears are their greatest hunting asset.
Hibernation & Breeding
Brown long-eared bats, both male and female, usually hibernate between November and April because they prefer the cold temperatures. They commonly spend hibernation in tunnels, caves and mines where the temperature is just above freezing.
During the Autumn, between October and April, mating occurs yet pregnancies are delayed until the spring. This is so they can gather in maternity roosts with 10-30 other pregnant bats; unusually, male brown long-eared bats join these roosts with their partner. Then, around late June to mid-July, a single bat pup is born and will become independent within 6 weeks.
Conservation Status & Threats
Every species of bat in the UK, including brown long-eared bats, are protected by law so it is illegal to disturb, injure or kill them. They are protected under the Wildlife and Countryside Act 1981, the Conservation of Habitats and Species Regulations 2010, Countryside Rights of Way Act 2000, Natural Environment and Rural Communities Act 2006, and the Wild Mammals (Protection) Act 1996. Also, they are a European Protected Species under Annex IV of the European Habitats Directive.
The main threats to these bats are predators, habitat loss and pesticides. Because of their hunting habits of flying low to the ground, this makes them vulnerable to attack by predators such as domestic cats, kestrels and owls. Furthermore, the use of pesticides and insecticides on land has reduced their abundance of prey as well as their roosting habitats.
Pesticides are commonly used on exposed timbers in old barns where bats are known to roost. Loss of woodland habitats, due to modern intensive agricultural practices and property developments, is also a great threat to brown long-eared bats.
Bat Surveys by Greenlight Environmental
No matter what, we don’t want to see these beautiful creatures in decline which is why we reiterate the importance of bat surveys and ecological assessments. At Greenlight Environmental, we can provide all of the essential protection practices for future developments so protected bat species are not endangered.