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.
Sheena Radford, Alison Ashcroft, BBSRC (Aug 2016), £457,215
Patricija Van Oosten-Hawle, Dave Westhead, An-Jung Chen, NC3Rs (Aug 2016), £354,456
Peter Henderson, EU - European Union
EU - European Union
(Jul 2016), £123,897
Adrian Goldman, EU - European Union
(Jul 2016), £116,290
Urwin, Howard Atkinson, NERC
(Jul 2016), £105,053
Eileen Ingham and colleagues in Engineering and M&H, EPSRC (Jul 2016), £3,867,449
Michael Colman, MRC (Jul 2016), £200,956
Tim Benton, Fresca Group Ltd
(Jul 2016), £52,082
Derek Steele, Sarah Calaghan, Chris Peers, BHF (Jul 2016), £819,241
Paul Millner and colleagues in Engineering and M&H, BBSRC (Jul 2016), £129,647
Vas Ponnambalam, Darren Tomlinson, Stephen Wheatcroft, BHF (Jul 2016), £107,359
John Colyer, Christian Teade and colleagues in M&H, Kidney Research Fund UK (Jul 2016), £39,964
Nicola Stonehouse, David Rowlands, World Health Organisation (Jul 2016), £656,545
Alexander Breeze, MRC
(Jul 2016), £403,513
Yoselin Benitez-Alfonso and colleagues in MaPS, Leverhulme Trust (Jul 2016), £353,301
Joan Boyes, Peter Stockley, Roman Tuma, David Westhead, Bloodwise (Jul 2016), £232,960
Edwin Chen, Leuka
(Jul 2016), £98,642
Helen Miller, Hamlet Protein A/S
(Jul 2016), £22,240
Alexander Breeze, Syngenta
(Jul 2016), £299,629
Alan Berry, Wellcome Trust
(Jul 2016), £599,375
Amanda Bretman, Elizabeth Duncan, Leverhulme Trust
(Jul 2016), £245,369
Andrew Macdonald, Neil Ranson, Richard Foster, Yorkshire Kidney Research Fund (Jul 2016), £51,368
Roman Tuma, Sheena Radford, BBSRC
(Jul 2016), £379,786
Adrian Whitehouse, Ian Carr, Worldwide Cancer Research (Jul 2016), £199,738
Paul Milner, Mike McPherson, Lars Jeuken, Darren Tomlinson and colleagues in Engineering & M&H, MRC (Jul 2016), £3,124,568
Helen Miller, Innovate UK (Jun 2016), £3,463,470
Adrian Goldman, Royal Society
(Jun 2016), £250,000
Jim Deuchars, Susan Deuchars, Shaunna Burke, Dunhill Medical Trust (Jun 2016), £86,570
Keith Hamer, Guy Ziv, DEFRA Dept for Env. Food & Rural Affairs
(Jun 2016), £300,122
Richard Bayliss, EU - European Union
(Jun 2016), £373,565
Sheena Radford, Eric Hewitt, Alison Ashcroft, Andrew Wilson, EPSRC (Jun 2016), £458,278
Jamel Mankouri, John Barr, British Lung Foundation
(Jun 2016), £24,000
Zahrah Timsah, Wellcome Trust (Jun 2016), £100,000
Andrew Macdonald, Kidney Research Fund UK
(Jun 2016), £63,653
Edwin Chen, Academy of Medical Sciences
(Jun 2016), £98,110
Adrian Goldman, Royal Society (May 2016), £250,000
Peter Stockley, Wellcome Trust (May 2016), £1,246,487
John Ladbury, Christopher Jones, Cancer Research UK
(May 2016), £6,905
Elton Zaqiraj, Wellcome Trust (May 2016), £1,093,823
Alison Baker, Miller Camargo-Valero, BBSRC
(May 2016), £553,691
Adrian Whitehouse, Julie Aspden, Ian Carr, BBSRC (May 2016), £466,043
Peter Urwin, BBSRC (May 2016), £432,379
John Trinick, Elwyn Issac, Leverhulme Trust
(May 2016), £171,742
, British Council, UK
(May 2016), £11,100
Mark Harris, Horserace Betting Levy Board
(Apr 2016), £10,000
Peter Stockley, Neil Ranson, Roman Tuma, David Rowlands, MRC (Apr 2016), £341,225
Jamel Mankouri, Royal Society (Apr 2016), £332,396
Andrew Tuplin, MRC (Apr 2016), £508,170
Simon Goodman, British Council, UK
(Mar 2016), £35,800
, British Council, UK
(Mar 2016), £12,802
Katie Field, NERC
(Mar 2016), £186,411
Isuru Jayasinghe, Royal Society
(Mar 2016), £14,919
William Hoppitt, EU (Feb 2016), £34,345
Helen Miller, ABNA Ltd (Feb 2016), £115,000
Sarah Calaghan, Isuru Jayasinghe, BHF (Jan 2016), £52,050
Edwin Chen, Wellcome Trust (Jan 2016), £98,341
Patricija Van Oosten-Hawle, Wellcome Trust (Jan 2016), £89,900
James Duce, Alzheimer's Society (Jan 2016), £84,834
Andrew Smith, Rosetrees Trust (Jan 2016), £20,000
Richard Bayliss, BBSRC (Jan 2016), £345,796
Richard Bayliss, Cancer Research UK (Jan 2016), £283,616
Richard Bayliss, MRC (Jan 2016), £200,088
Thomas Edwards and colleagues in the School of Chemistry, EPSRC (Jan 2016), £2,228,732
David Brockwell, Sheena Radford, BBSRC (Dec 2015), £358,570
Stephanie Wright, Kay Kendall Leukaemia Fund (Dec 2015), £207,286
Stefan Kepinski, Michelle Peckham, BBSRC (Nov 2015), £461,760
Ryan Seipke, BBSRC (Nov 2015), £340,536
Paul Knox, BBSRC (Nov 2015), £40,000
Helen Miller, Agriculture & Horticulture Develpmnt Brd (Oct 2015), £63,560
Jessica Kwok, Wings For Life Spinal Cord Research (Oct 2015), £134,981
Joe Cockburn, Royal Society (Oct 2015), £14,960
Alison Ashcroft, Peter Stockley, Sheena Radford, Nicola Stonehouse, David Brockwell, Darren Tomlinson, BBSRC (Oct 2015), £340,937
Alan Berry, Wellcome Trust (Oct 2015), £752,365