Goss's Rule and the Canines of Yellowstone

By Dave Hanks

GOSS’S RULE states: “When two species share the same habitat, and also share the same niche, the dominant species will push its competition out.” This is classic between coyote, fox, and wolf. Yellowstone Park provides a situation where this rule is very noticeable. Before the introduction of wolves, there were many coyotes and fewer fox. Since their introduction, wolves have expanded greatly, coyote numbers have decreased, and the Red Fox population has increased.

It stands to reason that size plays a big role in the dominance of these three canines. Wolves, especially when hunting in family packs (usually 4 to 7), can bring down larger prey than coyotes - hunting alone or even cooperatively. Also, bigger groups contribute to a species ability to dominate, and larger canine will kill the smaller ones when they catch them. I have witnessed wolves chasing coyotes that were brazen enough to approach a carcass fed upon by wolves. I have seen coyotes escape, but also observed one that was unlucky. Because the Red Fox feeds mainly on smaller mammals and birds, it is not as competitive to the wolf as it is to the coyote - which has an expanded diet.

Gray wolves look like large German Shepard dogs. Coyotes are somewhat smaller, lighter in coloration, and have a more pointed face. The Red Fox is considerably smaller, with a slender body, reddish tinge to its fur, and with a white tail tip.

Vegetation eaters, when their populations increase, have the ability to destroy their own habitat. Thus, predators keep these populations in balance. Predators are also breeding selection factors for prey species. They weed out the weak, the diseased, and the old (who no longer reproduce but still eat). Nature’s ways sound cruel, but they are necessary to keep herbivore numbers at the maximum that the habitat can withstand.

(A Gray Wolf: Top dog in the predator hierarchy)