POPULATION: 3.5-4 million worldwide, but some herds and subspecies at very low numbers Although the American herd of woodland caribou is at great risk of extinction, the ESA lists only one subspecies (R. t. caribou) as Endangered.The woodland caribou's drastic decline in the Selkirk Mountains shows clearly how ecosystems are thrown out of balance by human activities. Logging roads, for example, are often death traps for caribou -- particularly in the winter when snow piles high on either side of the narrow roads. Drawn by the salt used to melt ice on the roads, caribou get caught between the snow banks and can't avoid the big logging trucks. Both male and female caribou have antlers, and the smaller females are often mistaken for elk and shot by hunters. The death of a reproducing female is critical to such a small population because it means the death of potential future generations as well.