As rat populations spike across North America, scientists search for new ways to curb the critters.

It’s a pressing task, as scientists warn climate change is contributing to a perfect storm of rat-friendly conditions. And there’s a lot at stake. One rat expert calls them klepto parasites because they steal from us. Our health, our safety and our peace of mind.

It’s why in an alleyway in Chicago, an experiment led by a Canadian scientist is looking at an innovative way to reduce rat numbers using birth control.