This is scientific Americans 60 Second Science.

I'm Jason Goldman.

The little brown bat was once abundant in the eastern US,

but within the last 15 years, fungus called Pseudo-Gimnoaskis, Destructans,

infiltrated a cave in upstate New York. This fungus causes what's called white nose syndrome in bats.

The illness has now spread throughout North America causing widespread bat dieoffs.

But recently, little brown bats in New York have stopped declining. In fact, their numbers are actually going back up.

That was exciting, but we had no idea how these bats were persisting with the disease.

Harvard University epidemiologist Kate Langwig.

Little Brown bats during the fall swarm around hibernaculate entrances and during that time period

they're active and they're feeding and fattening for winter

they also mate during that time period.

Then they go into hibernation

and that's really when infection peaks.

Winter is sort of the time period in which Whiteness Syndrome is happening to bats.

To understand how the New York bats were surviving,

Languig and her team compared them to bats from Illinois and Virginia

in colonies that are still experiencing the initial

mass dieoffs.

They wanted to see whether the New York bats had simply found a way to tolerate the

presence of the pathogen or whether they'd actually developed resistance to the infection.

So we found that when bats first return to hibernacular, they still become infected.

...