Here's a good one from News of the Weird:

According to a January Los Angeles Times profile, biologist Gerry Kuzyk recently came upon, in a remote area of the Yukon, an 8-foot-high, half-mile swath of what he learned was caribou droppings; since no caribou had been sighted in the area for over 100 years, Kuzyk concluded that it was a massive, centuries-old accumulation that had been frozen but recently melted.