Moose in northern Canada are dying off at an alarming rate. The huge lanky animals are being assaulted by the tiniest of enemies: ticks. It's a natural cycle that happens every year, but it's much worse than usual this year.

"We've seen a major die-off," says Dan Strickland, Chief Park Naturalist. "We don't know how big; we just know it's really considerable."

Strickland spent the spring trying to count the losses. Now he's warning tourists about what they may see -- and smell-- along the trail: dead moose, in unusually high numbers.

The ticks cling to plants in the fall and then latch on to passing moose in the spring to feast on the blood and grow. Tens of thousands of ticks swarm the moose and ultimately kill them.

In just one week in April, a dozen moose were found curled up on the side of a highway. They were exhausted, drained and so itchy, they'd scratched off their hides. Most died from infection or hypothermia.

How is it that a huge moose cannot protect itself against a tiny tick? Some naturalists say it's a problem of evolution. The ticks were here first, and the moose arrived in this part of the world only 10,000 years ago. Even after that length of time, the moose still haven't developed a good tick defence.

Also working in the ticks' favour is a series of warm springs that has allowed the tick population to explode. Some are predicting that next year, the moose die-off could be even worse.

While the moose carcasses pile up, park naturalists say there is nothing they can do to help the moose in their fight against the parasites. They can only wait and let nature take its course.