The Natural History of Selborne.

This is the Rev Gilbert White who was a parson down in Hampshire throughout much of the 1700s and he used to wander around the lands of his parish looking at all the wildlife, and he was a tremendous observer and that’s what was so special about him. He wrote down everything he saw in a series of letters to Thomas Pennant, one of the famed natural historians of his time, a Welshman, and it’s a tremendous insight into the natural world of that time. For instance, he was noticing that swallows and martins and swifts disappeared every autumn. Nobody knew too much about migration. There was still a belief that swallows hid in the mud at the bottom of ponds during winter. They had no idea. But he did begin to believe in migration. He had some knowledge of what migration had been observed in Europe through his correspondence, and you can tell from his writing that he was trying to push Pennant into believing that migration occurred. Bat-wise, he only knew of two species of bat, one which we now call the pipistrelle and the other was the long-eared bat. There was also a bigger bat that he saw flying over and knew it was different. He eventually managed to ‘procure’ two of them (he shot them!) and they were a species that we now call noctule. This is the first record of this high-flying bat and it was him that identified them, so he was picking up new species at a time when there were no field guides, very little published information about wildlife. It’s really tremendous – he was also looking at plants and fossils. This was pre-Darwin so evolution wasn’t really known about, but he found fossils of long-dead sea creatures and it started him thinking. He was such a good observer and questioned everything he saw. It’s what we should all be doing nowadays – not accepting too easily what we read.

How many species of bats are there? He’d logged three.

There are 17 in the UK, possibly 18, but they all look very similar so it’s not surprising that he only knew of two of them at the time. The most recent discoveries of new species are only done using genetics.

What makes something a separate species?

It’s a group that won’t successfully breed outside of that species. Because bats look very similar to each other it’s hard to tell by looking at them and that’s often how these things get confused.

Mammals of the British Isles Handbook.

This is a wonderful tome. It’s a big book. It’s not the sort of thing you’d read on the beach or put in your handbag. It’s a monster book. It’s massive. It’s in its fourth edition now and has been coming out for 30 years and it’s a collection of all the mammals we know in the UK. It’s written not just by professionals but also by amateur naturalists that have been looking at a particular species for many years, sometimes all their lives, so it’s a tremendous insight into the mammals we have here. It’s really based around the work of the Mammal Society which assembles the knowledge of all these mammalogists together. Bat-wise it’s tremendous because a quarter of all the mammals in the UK are, in fact, bats.

A quarter of UK mammals are bats?

Yes. And it’s got all of them outlined in lovely detail and with such great insight because some people who study bats don’t just study bats, they study one species of bat and their whole life is spent looking at that one species. Every aspect of their life is covered.

Which species of bat have you spent your life looking at?

I’ve been looking at Daubenton’s bat. It’s known as the water bat, as it’s a specialist feeder of aquatic insects and it skims across the surface of still water, lakes, reservoirs and so on, snapping up the insects off the surface with its very large back feet. I’ve found out where these bats fly to, how far they can travel, what a group of these bats does, and how each individual is related to another.

Where do they live?

They usually live in hollows of trees overhanging or near to water. We’ve been tracking them now in my home area for 20 or 30 years or so and we put little rings on them so we can see individuals and see how far they travel.

How far do they travel?

They can go ten kilometres or more from the roost to a foraging area and they are travelling for a reason. Gilbert White was trying to get his head round this too. Why do they go so far when there’s apparently better feeding round where they live?

Why do you think they go?

I think they’ve got a very complex social structure, so they don’t live just in one little community. There are a number of communities that they go to over the period of a year or so, so they’re constantly moving between these communities, checking up on each other. It’s not just males/females meeting up, it’s also males and other males, females and other females, so there are roosts that are constantly changing depending on who’s present, like a series of hotels across the landscape. The individuals in the hotels change every night.

How many bats are there per roost?

That’s a very difficult question because the roost changes nightly, so one night a roost might have five bats in it and another night it might have 50. Just like a hotel – weekends it’s very busy. Having put a marker on the bat we have found that sometimes we might not see it again for 12 years until it comes back to that particular roost.

How long do they live?

Twenty or 30 years. The longest-lived record is of a Brandt’s bat, a small insectivore bat, that was found in Russia when 41 years old.

Tell me about Walker’s Bats of the World.

This really is an offshoot from Walker’s Mammals of the World by an American publisher who had got every single mammal in the world photographed and the bats bit was so popular that it was published separately. It’s got a good, clear summary of every species of bat that we knew then in the world. A few have been discovered since it came out, but it lists all 18 families, broken down into their species – a very good insight into all of the world’s bats. It tells us what they look like, numerous photographs and drawings and a general text on their ways of life with a simple thumbnail sketch. One trouble with bats is the lack of depth of knowledge we yet have of most species. As we speak some taxonomist is splitting one bat species into two species, and other bat species, of course, is becoming extinct, so species numbers are always changing. Some of the species mentioned in Walker’s are now extinct. They do have a pretty rough time and are more prone to extinction than many other mammal groups. You get things like typhoons that sweep across an island and wipe out all the fruit that the fruit bats feed on. That’s just one environmental disaster that can cause a bat extinction.

Bats are very mobile so they have, over millions of years, spread to all parts of the world apart from the two poles and some very high points like Everest. Most of the species are in the tropics because you have most of the food types, most of the fruit and the insects. The smaller the land mass the fewer species you get. Mainland Europe has 30 or 40 bat species, the UK has 17, Ireland has eight or nine, so it gets fewer as it gets smaller. There are about 5,000 mammal species in the world and 1,100 of those are bats. The fruit bats, or flying foxes, that we know about from the old world tropics, Australia, Africa, South East Asia, are a big group with around 180 species. All the others are insect-eating bats (although some also eat fruit).