Most of us will be aware of that moment just before dark when something flits across our line of vision and a moment later we think “Oh, a bat!” If you work, rest or play in the Lune Valley you are probably more aware than most, because it is a real hotspot for all the species of bats found in Lancashire.

All UK bats enjoy a very strict level of protection in law and it is an offence to harm, kill or disturb bats, or to destroy or obstruct the places that they use for shelter – their roosts. And because bats change roosts but return to places they have used before, this means that roost sites are protected even if the bats are absent at the time. So advice from Natural England should be sought if you are planning to do anything that might affect bats and this is an important service designed to keep people on the right side of the law.

You might be surprised to know that at least eight species of bats are regularly found in the Lune Valley. Since they all depend to a greater or lesser extent on the built environment for their roosting requirements, every one of us has the potential to help or hinder their conservation. Bats can be very inconspicuous, entering buildings and other structures only through existing gaps and crevices which need be as little as 15mm in size. They do not usually cause any damage to the structures they use; bats spend a lot of time grooming, don’t build nests or take materials into their roosts and don’t chew or gnaw wood or wires.

Bats are unusual small mammals because they are long lived and breed slowly. Bats mate in autumn but females do not give birth until summer; if the baby is lost it is a full year before she gets another chance. So populations cannot just bounce back if they start to decline.

Bats are at their most conspicuous and vulnerable to disturbance in the summer when nursery colonies form consisting of many adult females bats which give birth, usually in June, to a single pup. The baby bat suckles for six weeks and starts to fly at three weeks old. If mum has to move roosts in a hurry before this point, a baby bat may cling on underneath her when she flies or it may be left behind, helpless.

All our bats are insectivorous and to survive the winter months when insects are in short supply, they hibernate to save energy. This is also a risky time for bats; if they are disturbed from hibernation, they may die because their reserves of fat are used up too early.

The most common species that occur in the Lune Valley are the Pipistrelles – Common (Pipistrellus pipistrellus) and Soprano (Pipistrellus pygmaeus). These are Britain’s smallest bats weighing only five grams and being about 3cm long. The two species have different echolocations calls when heard on a bat detector but are very similar to look at.

Common pipistrelles are widespread and mobile, colonies often move around between similar modern houses in response to the time of year, weather or some other requirement that we can only speculate about. They usually roost under slates, fascia boards or hanging tiles and there is rarely any evidence of them inside the building. They are also found in older stone buildings and even in newly converted barns where they may roost between the external stone and internal block walls, sometimes moving in almost as soon as the people!

Large nursery colonies of Soprano pipistrelles are known in the Lune Valley and the river itself is an important foraging place for this species, as well as for the Daubenton’s or Water bat (Myotis daubentonii). Crevices in the stonework of bridges or tunnels and rot holes in large trees are the favoured roosting places for Daubenton’s bats and so the Lune Valley provides ideal conditions for them.

The Brown long-eared bat (Plecotus auritus) is very dependant on woodland for foraging and is found in the more rural areas along the valley. This is a slow flying bat and often hovers to glean moths and other large insects from the foliage of trees. Usually found in older houses where the roof void is uncluttered, once they have found a roost that suits them, they tend to stay put.

Unlike Pipistrelles, which are crevice dwelling bats, they can be easy to spot as they tend to roost in a big clump on a beam or rafter. But consider the number of lofts and barns that have been converted in recent years and it is obvious that populations of our long eared bats must be facing a great deal of displacement and disturbance.

Our most enigmatic bats are probably the closely related Whiskered (Myotis mystacinus) and Brandt’s (Myotis brandtii), small bats that turn up regularly in this area – there is a nursery colony near the Crook’o’Lune – but about which we know next to nothing. Another relative – the Alcathoe’s bat (Myotis alcathoe) – is probably also present but not yet identified.

Noctule bats (Nyctalus noctula) are our largest species, weighing about 30 grams and can often be seen flying high and fast at sunset with swallows and swifts. This is the species least reliant on buildings, usually being found in trees where they roost in old woodpecker holes or rotten branches. They can be difficult to find as they move roosts frequently so special care is needed when felling veteran trees with features such as cracks, splits, loose bark or hollow branches. Another species under stress, any area with large mature trees along the valley may be important for them.

In winter, cool and stable conditions allow bats to save energy by hibernating; they do not need to use up their bodily reserves to keep warm. High humidity is important as well, meaning that bats do not lose moisture through their extensive skin membranes so don’t need to wake up very often for a drink.

Some bats hibernate in the cooler parts of buildings such as slightly rotten wooden fascia boards so take care when carrying out repair works even in the depths of winter.

Some species will move to upland areas in autumn using the river and it’s tributaries as their motorways to migrate along. They use caves for hibernation but before that they “swarm” for several weeks. Research continues to try to find out more about this behaviour but it is best thought of as the bat equivalent of a nightclub; where bats go to meet new bats. The swarm can consist of many hundreds of bats which may have travelled a long way to be there. This must mean that these upland areas near caves and the commuting routes to and from them are absolutely vital and the loss or severance of a single one may make a huge difference to their continued survival.