US bats’ highway bridge roosts

This video from the USA is called Texas A&M Researcher Explains Bat Love Songs.

From the BBC:

Concrete bridges could make better roosts for certain species of bat than natural caves, according to research.

Scientists in the US monitored the birth weight and growth of bat pups that were born under bridges over busy freeways, and pups born in caves.

They found that, rather than the relatively noisy man-made roosts being detrimental to the animals, pups born in bridges were larger and grew faster.

The findings are reported in the Journal of Zoology.

Lead researcher Louise Allen told BBC News that, because the Brazilian free-tailed bats she studied live in such large colonies, it is very difficult to repeatedly recapture and study them.

“You can’t really do whole-life reproductive studies on them,” she said. “So as a [measure] of reproductive success, I looked at birth size and how fast they grew.” …

“Not only were the bats in the bridges larger, they also grew faster,” she told BBC News.

“They reached the size where they could go and start foraging on their own up to five days earlier [than the bats born in the cave].”

This finding was contrary to what the scientists expected.

They initially thought the environment – with traffic noise and pollution – would be “stressful” for the animals.

“In a stressful environment, animals often put reproduction to the side and concentrate on survival.”

But when it comes to living above a busy road, it seems the benefits for these bats outweighed the disadvantages.

“The [bridges] are often closer to foraging sites and they are warmer,” explained Dr Allen.

“So they can spend less time on thermal regulation and put more of that time into fat stores and bone growth.”