About bats
About bats
What is a bat?
Bats are amazing. They are the only truly flying mammals. British bats eat nothing but insects, which they usually catch in flight, using echo-location, although some bats can pluck insects off foliage and grasses. In one night a tiny pipistrelle can eat up to 3000 insects.
Bats give birth to live young; in the UK this is usually a single baby, which is suckled on mother's milk like other mammals. Babies are mostly born in June (or sometimes in July) and for this major event in a bat's year, the females gather in maternity roosts (also sometimes known as nursery roosts).
When the babies are old enough to fly, at about three weeks old, they start to catch insects for themselves. At this time, they are a bit like human toddlers, not too sure of their wings, and may become grounded through dehydration or starvation. They may also lose their way and end up in inappropriate places, such as inside buildings, having mistaken an open window for their roost entrance.
Photo used with kind permission of Robert Stebbings/BCT
In August/September the females go to look for a new mate. Then they, and the young ones, spend the short autumn before the cold weather sets in, feeding to put on good stores of body fat to see them through the long period of hibernation. Lack of their insect food means they must hibernate from around October through until the end of March.
Photo used with kind permission of Robert Stebbings/BCT
When the weather warms up in spring, the females, who have stored their mates' sperm in their bodies all winter, become pregnant and once again seek out their traditional maternity roosts.
Where do bats live?
Bats need a variety of roosts and feeding habitats to sustain what can be a precarious life cycle.
When the female bats gather to give birth, they seek out traditional summer roosts that may be used over many years. These roosts need to be warm enough that the females can save energy and the babies do not become chilled when the mothers go out to feed. Most British bats use buildings, and some, like long-eared bats, serotines and the greater and lesser horseshoe bats, are extremely dependent on buildings. Modern and older houses, churches, larger buildings and occasionally barns, stables and bridges may be used. Holes, hollows, crevices and loose bark in trees also provide roost sites, especially for species like Daubenton's, noctule and the rare Barbastelle bats.
Photo used with kind permission of Robert Stebbings/BCT
Some bats feel safest roosting in spaces and crevices (photo of pipistrelles with caption).
Others prefer to use the roof void, so that they can roost in different parts of the roof, depending on weather conditions. For instance, when it is very hot, they may need to move to the more shady, north side of the loft.
Photo used with kind permission of Maggie Frankum
Threats to bats
All British bats have declined dramatically over the last 50 years. Even our most common bats, the pipistrelles, appear to have suffered a serious decline, and 12 of the UK's 17 species are considered rare or vulnerable. For instance, in Leicestershire and Rutland, we have noticed that over the last 25 years, sightings of noctule bats have become less frequent.
Threats include:
- Loss of feeding habitat e.g. hedgerows, old trees and species-rich grassland, drainage of wetland, increased use of pesticides;
- Loss of roost sites in buildings and trees, e.g. from loft and barn conversion, re-roofing, soffit replacement, timber treatment and other renovations;
- Loss of hibernation sites, e.g. buildings, tunnels and trees from development or vandalism.
What if I've got bats in my roof?
Bats can take up residence in the eaves, soffits, cavity walls or loft space of your home. They are not pests and do not damage the fabric of your home. Bats do not build nests, and their droppings are dry, crumbly and non-corrosive. They eat only insects, many of which we consider to be pests. All in all, they should be welcome guests.
However, some of our activities can harm them, so if you have bats in your home you must contact English Nature (or other statutory nature conservation organisation) for advice before doing anything that may disturb them or their roost. This could include repairs or improvements to the roof, soffits or loft, and this advice aims to provide a way to achieve the required work without harming the bats.