"I know there aren't any bats..."

In my work I meet many bat roost owners, varying in attitude towards "their" bats from delighted to appalled and all points in between. I also encounter many people who are commissioning a bat survey because they have been obliged to do so. Often in the UK this occurs when someone applies to their local authority for planning consent to carry out work on a building. The law requires the local authority to consider protected species, so if there is any possibility for a bat roost to be present a bat survey must be carried out. "I know there aren't any bats there, but we have to have a survey" is often the client's opening gambit. It's not an unreasonable attitude: what little most people know about bats leads them to expect them to be highly visible, extremely rare and likely to roost in caves or gothic castles. Against that background it seems insane for a local authority to request a bat survey of a three bedroom suburban house, a 1970's primary school or a city centre council flat. Yet I and my colleagues frequently come across bat roosts in buildings like these.

This modern primary school is home to 280 Soprano Pipistrelles. They roost alongside the main entrance and most people think the noise is made by nesting birds.

Part of the problem is one of perception - bats are rare, that's why they're protected. Yet some bat species are very common. Here in central Scotland Soprano and Common Pipistrelles and Daubenton's Bats are all common, but have the same level of protection as rarities such as Whiskered Bats or Nathusius' Pipistrelles. Rarity isn't the sole reason for protection - vulnerability is a key issue. Our commonest species (in central Scotland), the Soprano Pipistrelle gather in their hundreds and even thousands to breed. The destruction of one of these roosts could harm the species over a large area. Bats reproduce very slowly - a single female will often only have one offspring in a good year and the need to gain weight swiftly in order to survive hibernation means that many do not survive. Thus bats are usually slow to recover from set-backs. Reducing prey availability caused by pesticides, illegal roost destruction through prejudice and stupidity and a host of other factors all combine to make legal protection essential.

Another factor in the misconception is the expectation that bats are visible in their roosts. We have Hollywood to thank for that. People expect to glance inside an attic and see a host of bats hanging from the ceiling, with their wings wrapped around their bodies. In the case of Horseshoe Bats that genuinely is the case, though bats tend to be a great deal smaller than they appear to be when in flight. Most other bat species in the UK roost in holes or crevices of one type or another, meaning that when they roost in buildings they are less likely to be visible to the uninitiated. Not long ago I surveyed a farm, the owner of which insisted there were no bats around his farm. Not only were there three species of bats roosting in his farm, there was a colony of about 80 Common Pipistrelles roosting alongside his bedroom window.

This colony of Brown Long-eared Bats are tucked into a crevice between two roof beams. If disturbed they tend to move deeper into the crevice, out of sight.

I'm not sure where the popular conception that bats only roost in old buildings comes from. It's certainly true that large country mansions and castles usually do contain bat roosts, but this often has as much to do with the presence of undisturbed spaces and the maturity of surrounding habitat as anything else. Modern house builders are surprisingly good at including loose-fitting fascia boards, poorly attached flashing and many other features which bats find to their liking and it is usually in modern buildings that people are particularly surprised to find bats.

Not a building which fits with the popular vision of a building used by roosting bats, but 800 Soprano Pipistrelles roost under the slates of this house every summer.

I have no doubt that there are many buildings around the country containing bat roosts that the owners are unaware of. Either they don't notice the signs or don't recognise them for what they are. Two years ago I spent a couple of weeks flying (when I'm not working with bats I fly gliders) from an airfield in Leicestershire. The club house there is a single-storey, L-shaped building about five years old. In the shelter of the L-shape are comfy tables and chairs, accessible from the bar. It's a nice place to sit on a summer evening and is well-used by club members. I had only been there a couple of days when I realised that a colony of Common Pipistrelles were roosting  at the wall-head alongside these tables. Each evening as the sun started to go down around ten bats would emerge and fly through the group of people who were sitting drinking and chatting. Nobody ever noticed them! I suspect people occasionally glimpsed a bat and assumed it was a songbird. The club management were entirely unaware of the presence of a bat roost in their recently-build clubhouse. If they applied for planning permission to change it and were asked for a bat survey I expect they would be astonished and annoyed at being asked to commission a bat survey...

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What's in a city?

In modern Britain we live in a man-made landscape. Whether you look at stone walls and sheep folds on a remote hillside in Sutherland, a leafy farmscape in Devon or a built-up part of south east England, man's handiwork is there to be seen, profoundly affecting the habitats available to our wildlife and of course, our bats.

I have always found it interesting to place wildlife within the landscape: where do they live? Where do they forage or hunt? How do they move through the landscape? Where are they present or absent? Where are they threatened by predators and where do they take refuge?

We are fortunate in the 21st century to have easy access to satellite photography free of charge, via websites such as Google Earth and Bing Maps, which allow us to explore this swiftly and with a nice glass of Merlot to hand!

I thought it might be interesting to look at a random square kilometre of a major city and see what habitats useful to bats would be apparent, using one of these websites.

Here is my square kilometre. Two things instantly spring out: this is very obviously a built up area, but there are clearly green places here. Are they just amenity grassland, or more structural habitats which might they offer hunting places for bats. And are they connected, allowing bats to move through the city?

Zooming in makes some of these habitats more apparent. Here, the classic suburban wildlife habitat displays it's strength. These gardens may be individually small, but together they form a block of habitat, with trees and shrubs providing potentially good foraging habitat for generalist species, such as Common Pipistrelle (Pipistrellus pipistrellus) and Soprano Pipistrelle (Pipistrellus pygmaeus). In the south Soprano's tend to have a riparian affinity, but here in Scotland they are more numerous than the Commons and tend to use a wide variety of edge and suburban habitats.

Also in my square kilometre is another classic urban wildlife habitat: a cemetary. I recently carried out some bat surveys close to a large cemetery in East Kilbride and was delighted by the number of Foxes which emerged from it each night, to keep my survey team company. On one memorable evening two of us watched a young Fox edge up to within a few feet, grab a plastic bottle and run to a safe distance with it. Apparently unimpressed it then urinated on the bottle and stalked off!

This cemetery appears to enclose a lot of mature trees. These are likely to harbour plenty of insect prey for bats, especially if some of them are native species. Non-natives tend to be home to generalist invertebrates, but native species are also likely to offer a home to many more native invert species, for whom the tree provides more specialist niches.

Also in the square kilometre is what appears to be a public park, probably offering similar foraging habitat for bats (though not necessarily undisturbed conditions to allow Foxes to successfully breed!) So with a cemetery, a public park and plenty of mature gardens our city bats seem to be quite well-provided with foraging habitat. There are also plenty of houses and industrial buildings which seem likely to provide the potential for roosting Pips and some of the more mature trees could include holes and crevices for roosting bats too. The next question is how do the bats move between all the features? What commuting corridors are available to them?

Often lined with trees and shrubs, urban railways offer excellent wildlife corridors and this square kilometre has several. Here two cross each other and elsewhere a disused railway line has been developed into a cycleway. I'm sorry to revert to a foxy, rather than batty theme, but I was travelling on a train in Ealing which stopped at signals. Right outside the carriage window a vixen relaxed in the sun, whilst her three cubs played, completely unperturbed by the proximity of a trainload of disgruntled commuters!

Even better, within this square kilometre is the mother load: a stretch of canal. With trees, shrubs and hedges providing security for commuting bats and foraging opportunities for Soprano Pips, this is an excellent wildlife corridor. Emergent and submerged vegetation provides homes for plenty of invertebrate prey for Daubenton's Bats (Myotis daubentonii) and the smooth water is perfect for them to hunt over. Smooth water helps echolocating Daubies to pick up emergent insects on or just above the surface.

Canals without vegetation are not necessarily poor foraging places. A few years ago I surveyed the Union Canal with a team of volunteers, attempting to map foraging sites. To my surprise, the most active foraging sites were the ones with little or no vegetation, rather than those with plenty of vegetation and diverse prey species. These concrete-lined canal sections had large numbers of Chironomid midges hatching. They are amongst the first species to occupy stagnant water and the bats demonstrated that, as far as they were concerned, quantity trumped diversity!

The next time you encounter a bat, try using this method to look at the surrounding habitat. You may be surprised how much you can conclude about likely hunting locations, commuting routes and possible roost sites which the bats may use.

My website: http://www.plecotus.co.uk/