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.
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 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 there's less time for good personal hygiene. Parasites not only make life uncomfortable but can
|Contact: Chris Bunting|
University of Leeds