From the transcript

Caribou were delayed an average of about a month in years when more than 5% of the herd migrated through that area. It took sometimes up to 2 months for caribou to get across the road. And some caribou crossed the road relatively easily, as if, you know, the road hadn't been there. But the average over all those years was that more than 50% of the caribou were delayed by the road. When they migrated by Red Dog.