Twenty-two species of bats make their own homes by strategically gnawing on large tree leaves in such a way that the leaf folds over to shelter a small group of bats. These are the tent-making bats, and their "tents" offer cover from predators, protection from weather and roosting sites close to foraging habitat.
But, The Economist magazine of London notes, some leaves make much better tents than others, and the difference can have a big impact on bat behavior. Some tents last up to a year or more, while others fall apart in a few weeks. Meanwhile, some groups of tent-making bats stick together for long periods, while other groups disperse rather quickly.
Researchers Maria Sagot and Richard Stevens of Louisiana State University in Baton Rouge, Louisiana, suspected there "there might be a link between how socially integrated a bat colony is and the nature of its tents," the magazine said. "Indeed, there is. But the details of the link surprised them."
To explore that possibility, the researchers searched the scientific literature for information on bats' social systems and tent lifespans. They found relevant data on 15 of the 22 species, The Economist reports, and performed a series of statistical correlations.
In a report in the journal Biotropica, Sagot and Stevens said 10 of the 15 species build their tents from palm leaves and other sturdy plant materials that can last more than a year. The other five species are stuck with less-sturdy herbaceous plants that typically provide less than two months of shelter, said The Economist article. Only four species are formed groups that lasted at least a year.
"These, it might be expected, would be among the favored builders-from-palm," the magazine said.
But it did not turn out that way. In what they described as a surprise, the scientists determined that "four of the most sociable species are among those forced to use herbaceous plants, and thus to build ramshackle homes," according to The Economist. "The need to build a new place to live every few weeks trumps familiar domestic comfort as a promoter of social cohesion."
The researches said that a nomadic lifestyle that's required by short-lived building materials might be possible only for species that are able to collaborate, according to the magazine.
But they said another alternative might be more likely. The four "collaborative species" are not closely related. "That there are no highly social bats which build long-lasting tents, suggests it is the instability of the dwelling that is driving the evolution of the behavior," The Economist reports. "As in people, so in bats: adversity promotes solidarity."