Bats Split On Family Living

Jan. 24, 2013 — For the tiny Daubenton’s bat, the attractions of family life seem to vary more with altitude than with the allure of the opposite sex.

Map showing the location of bat roosts in the Yorkshire Dales. (Credit: Image courtesy of University of Leeds)

For more than a decade, a team led by Professor John Altringham from the University of Leeds’ 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 Daubenton’s 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 won’t let them in the roost. They don’t 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 together — the 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 there’s less time for good personal hygiene. Parasites not only make life uncomfortable but can affect a bat’s 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 Daubenton’s 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 doesn’t 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 Daubenton’s 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.

 

Story Source:

The above story is reprinted from materials provided byUniversity of Leeds.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Journal Reference:

  1. Ruth L. Angell, Roger K. Butlin, John D. Altringham.Sexual Segregation and Flexible Mating Patterns in Temperate BatsPLoS ONE, 2013; 8 (1): e54194 DOI:10.1371/journal.pone.0054194
University of Leeds (2013, January 24). Bats split on family living. ScienceDaily. Retrieved January 30, 2013, from http://www.sciencedaily.com/releases/2013/01/130124183638.htm

Mother Bear Knows Best Place to Call Home

Jan. 21, 2013 — Mama bear appears to know what’s best when it comes to selecting a place to call home, according to a new University of Alberta study.


The research, which may ultimately help protect Alberta’s dwindling population of grizzly bears, is among the first of its kind to test the nature-versus-nurture debate on how large, free-ranging wildlife select habitat.

Lead author Scott Nielsen, assistant professor in the Department of Renewable Resources, and head researcher in the U of A’s Applied Conservation Ecology (ACE) Lab, teamed with one of the lab’s post-doctoral fellows, Aaron Shafer, and professor Mark Boyce of the Department of Biological Sciences for the four-year study.

Published in the latest issue ofPLOS ONE, their work explored whether the maternal rearing of cubs shaped which habitats grizzly bears eventually choose. The findings “suggest that habitat selection is learned by young grizzly bears from their mothers and would likely be a more adaptive strategy than using instinct,” Nielsen said.

“There are a number of strategies that appear to be handed down from generation to generation from mother to offspring. It’s the ‘nurture’ side of the equation that is shaping the life of the bear.”

The study is part of ongoing work by Nielsen and a team of master’s students and PhD candidates who study conservation issues related to species at risk, such as grizzlies, to help in their population recovery. Other current research includes work on lizards, otters, boreal forest biodiversity and restoration of degraded ecosystems.

Through the ACE lab, U of A scientists are identifying critical habitats and needs of threatened species such as grizzlies, and determining the most effective management actions for their recovery.

The grizzly study, conducted in the foothills of west-central Alberta, tracked 32 adult and young grizzly bears that had been fitted with GPS radio collars. The animals’ movements were monitored from 31,849 locations spanning 9,752 square kilometres.

Nielsen and his team observed that genetically related female bears shared habitat selection patterns regardless of their location, whereas male bears related to one another did not.

“This suggests that there are different habitat selection strategies used by grizzly bears and that these are learned early in life, because male bears don’t participate in parental care,” Nielsen said.

The grizzly is considered a threatened species in Alberta (there are fewer than 700 in the province), and if their habitat-use strategies are indeed learned from early experiences, “then the habitats chosen for relocation of ‘problem’ bears or to supplement threatened populations would be important,” Nielsen said.

Knowing that habitat selection is part of a learned behaviour, conservationists tasked with relocating bears far from the animals’ known environments should pay close attention to the habitats into which they are released, he added.

The research was funded by the Natural Sciences and Engineering Research Council of Canada, the Alberta Conservation Association and partners from the Foothills Research Institute Grizzly Bear Program.


Story Source:

The above story is reprinted from materials provided byUniversity of Alberta. The original article was written by Bev Betkowski.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Journal Reference:

  1. Scott E. Nielsen, Aaron B. A. Shafer, Mark S. Boyce, Gordon B. Stenhouse. Does Learning or Instinct Shape Habitat Selection? PLoS ONE, 2013; 8 (1): e53721 DOI:10.1371/journal.pone.0053721
University of Alberta (2013, January 21). Mother bear knows best place to call home.ScienceDaily. Retrieved January 27, 2013, from http://www.sciencedaily.com/releases/2013/01/130122111752.htm