For more than a decade, a team led by Professor John Altringham from the Faculty's School of Biology has studied a population of several hundred bats along a 50-km stretch of the River Wharfe. They monitored roosts in Ilkley and Addingham, upstream in the market town of Grassington and higher still in the villages of Kettlewell and Buckden.
The researchers found that all Daubentons bats in nursery roosts in lowland areas of Wharfedale during the spring and summer were females and their offspring.
Male bats were mostly restricted to a windier, Heathcliff-like existence in roosts at the top of the Dales.
But the researchers were surprised to find a small oasis of cohabitation in Grassington, sandwiched between the bustle of the women-only childrearing in the lowlands and the more relaxed lives of the bachelors in the highlands.
Professor Altringham said: Low down the dale, the females appear not to tolerate males and we assume they wont let them in the roost. They dont want anything to do with them. High in the dales, all the roosts are bachelor pads. But in the middle, at Grassington, males and females live togetherthe social structure changes with the environment
One possible reason for not finding males low down the valley could be that the mothers just want to avoid competing with males for food. It takes a lot of insects to make the milk needed to feed their young, Professor Altringham said.
But it is also possible that the males choose not to roost with the females. When you look at the nursery colony in Ilkley, mothers and pups often have a lot of ectoparasites like ticks and mites. In a warm, crowded nursery, parasites can thrive, especially if theres less time for good personal hygiene. Parasites not only make life uncomfortable but can affect a bats health. The males that live by themselves are usually very clean in their bachelor pads, so you can understand why they might not want to move in, he added.
At Grassington, which is deep in the Yorkshire Dales National Park but not as high as Buckden and Kettlewell, the bats have a completely different social structure. Both male and female bats live with the young throughout the spring and summer in roosts in the stonework of the old Dales bridges and in holes in ash trees.
Females may roost as high up the dale as Grassington because they have these warm, cuddly males to bunk up with. This way, females use less energy keeping warm and babies grow faster, Professor Altringham said.
In these marginal conditions, they may just tolerate a few males to keep them warm. Otherwise they kick them out. Why do the males co-habit if they are going to get parasites all over them? Well, that may be down to the usual answer: sex.
Although male and female Daubentons bats usually live apart throughout the spring and summer, they meet when they begin flying to caves in late summer.
Professor Altringham said: In and around these caves the bats gather in huge numbers to mate, in a behaviour known as swarming. This is clubbing for bats, with males displaying to females in lengthy acrobatic chases. As winter closes in, these caves will ultimately be their hibernation sites.
"There are nearly 2,000 cave entrances and hundreds of kilometres of cave passages in the Dales and these attract bats from all over Yorkshire, Lancashire, Cumbria and beyond for mating and hibernation. The males in Grassington may be giving themselves the opportunity to mate with the females late in the summer before they even get to the caves.
The researchers have built up a detailed picture of social and sexual behaviour by genotyping hundreds of individuals. The evidence gathered from this supports the theory that the Grassington males enjoy an advantage in mating.
At Grassington, most of the fathers of bats born there spent the summer with the females. If we look at pups in Addingham and Ilkley, their dads were males caught when swarming at caves. So, as well as two different mating systems, you have distinct social groupings. A bachelor from Buckden is always a bachelor from Buckden. He doesnt pop down to Grassington to visit the females in the summer. His only option seems to be to go clubbing in the autumn, Professor Altringham said.
The Daubentons bat, named after the 18th Century French naturalist Louis-Jean-Marie Daubenton, is widespread across the United Kingdom and specialises in hunting insects over water. Full-grown adults weigh only 7 to 12 grams, but they can live for 20 years or more.
These bats are the size of a shrew but have a very different lifecycle. A shrew typically spends its entire life in a few metres of hedgerow, eats and breeds with a ferocious intensity, for a year if it is lucky, and then dies. In contrast, these bats lead a complex life over a huge area and females produce only one pup a year, Professor Altringham said. This makes bats particularly vulnerable to the problems of habitat fragmentation and climate change.
The paper, which is published in PLOS ONE, was co-authored by Dr Ruth Angell and Professor John Altringham at The University of Leeds and by Professor Roger Butlin at Sheffield University. It was funded by a Natural Environment Research Council (NERC) PhD studentship to Ruth Angell, with additional support from the NERC Biomolecular Analysis Facility at Sheffield.
Neil Ranson, Mark Harris, Ade Whitehouse, Peter Stockley, Sheena Radford, Alan Berry, Wellcome Trust (Mar 2016), £1,000,000
Katie Field, BBSRC (Jan 2016), £830,381
Alan Berry, Alex Breeze, Adam Nelson, BBSRC (Jan 2016), £479,490
Alan Berry, Wellcome Trust (Oct 2015), £752,365
Julie Aspden, MRC (Oct 2015), £633,020
Steve Sait, NERC (Oct 2015), £386,061
Urwin, Howard Atkinson, BBSRC (Oct 2015), £200,293
Eric Hewitt, Andrew Macdonald, Yorkshire Kidney Research Fund (Oct 2015), £46,621
Ade Whitehouse, Alison Ashcroft, Ian Carr, BBSRC (Sep 2015), £438,975
Dave Westhead, Leukaemia & Lymphoma Research
Leukaemia & Lymphoma Research (Sep 2015), £430,567
Shaunna Burke, Andrea Utley, Sarah Astill, Arts Council of England (Sep 2015), £80,594
Samit Chakrabarty, Ronaldo Ichiyama, Intl Foundn for Research in Paraplegia (Aug 2015), £93,000
Eileen Ingham, John Fisher, EPSRC (Jul 2015), £1,458,439
Anastasia Zhuravleva, BBSRC (Jul 2015), £483,019
Alex O'Neill, MRC (Jul 2015), £249,822
Ade Whitehouse, Richard Foster, Cancer Research UK (Jul 2015), £201,034
Ronaldo Ichiyama, Jim Deuchars, Sue Deuchars, Wings For Life Spinal Cord Research (Jul 2015), £123,895
Helen Miller, ABNA Ltd (Jul 2015), £22,968
Martin Stacey and colleagues in FMH, MRC (Jun 2015), £426,475
Adrian Goldman, Sarah Harris, Roman Tuma, BBSRC (Jun 2015), £420,693
Elwyn Isaac, EU (Jun 2015), £238,915
Christine Foyer, BBSRC (Jun 2015), £160,401
Adrian Goldman, EU (Jun 2015), £116,331
David Brockwell, Sheena Radford, Innovate UK (Jun 2015), £113,378
Yoselin Benitez-Alfonso, EPSRC (Jun 2015), £93,672
Michelle Peckham, Peter Knight, Thomas Edwards, BBSRC (May 2015), £404,987
Michelle Peckham, Ed White, Peter Knight, BHF (May 2015), £208,184
Dave Westhead, Sheena Radford, Alex Breeze, BBSRC (May 2015), £51,021
Steve Clapcote, Vitaflo International Ltd (May 2015), £33,703
Les Firbank, Joe Holden, Pippa Chapman, NERC (Apr 2015), £388,726
Samit Chakrabarty, David Steenson, BBSRC (Apr 2015), £120,103
Paul Millner, Gin Jose, Sarah Aickin, DSTL Porton Down (Apr 2015), £63,407
Chris Hassell, David Lewis, The Physiological Society (Apr 2015), £6,900
Andrew Tuplin, Royal Society (Mar 2015), £15,000
Yoselin Benitez-Alfonso, Royal Society (Mar 2015), £14,770
Patricija Van Oosten-Hawle, Royal Society (Mar 2015), £13,960
Stuart Egginton, BHF (Mar 2015), £272,979
Keith Hamer, Department of Energy & Climate Change (Mar 2015), £58,066
Andrew Macdonald, Yorkshire Kidney Research Fund (Mar 2015), £41,171
Les Firbank, DEFRA Dept for Env. Food & Rural Affairs (Feb 2015), £20,000
Ian Hope, Marie-Anne Shaw, BBSRC (Jan 2015), £381,998
Paul Knox, BBSRC (Jan 2015), £5,000
Andrew Peel, BBSRC (Jan 2015), £359,077
Christine Foyer, BBSRC (Jan 2015), £408,334
Dave Westhead and colleagues in Experimental Haematology, Cancer Research UK (Jan 2015), £700,521
Mike McPherson, Christoph Walti, DSTL Porton Down (Jan 2015), £625,125
Sheena Radford, Mark Harris, Peter Stockley, Alan Berry, Alex O'Neill, Thomas Edwards, Adrian Goldman, Anastasia Zhuravleva, Wellcome Trust (Jan 2015), £443,015
Alison Ashcroft, Peter Stockley, Sheena Radford, Nicola Stonehouse, David Brockwell, Darren Tomlinson, BBSRC (Jan 2015), £340,937
Bill Kunin, EU (Jan 2015), £157,490
John Colyer, Leeds Teaching Hospitals Charitable Fund (Jan 2015), £40,000
Chris Hassall, Royal Society (Dec 2014), £14,500
Ryan Seipke, Royal Society (Nov 2014), £13,700