‘Like butter for bears’: the grizzlies who dine on 40,000 moths a day

The tiny army cutworm moth provides a surprisingly nutritious meal for the giant carnivores - but humans are getting in the way

The barren mountain slopes of north-west Wyoming might seem like inhospitable territory for a hungry grizzly bear. Big game animals are few and far between, and blueberries don't grow from these rocky hillsides, high above the treeline.

But for a couple of months each summer, this stark landscape becomes a high-calorie buffet for hundreds of grizzly bears in the Rocky Mountain west. And it's all thanks to a small, unassuming insect whose relationship with the grizzly is as essential as it is unexpected.