Did you know that the last pack of grey wolves was eradicated from Yellowstone National Park in the 1920s. And it was at this time that the park’s entire ecosystem changed. In 1974 the gray wolf was listed as endangered and recovery of this species was mandated under the Endangered Species Act. It wasn’t until 1991 that Congress appropriated money for wolf recovery. After 160,000 public comments were received (the largest ever on any federal proposal at that time), 41 wolves from western Canada and northwestern Montana were relocated to Yellowstone. Not only are wolves now “delisted” as an endangered species throughout the northern US Rocky Mountains, including Wyoming (there are about 450-500 in Yellowstone alone), but their recovery triggered one of the most remarkable trophic cascades ever.
Trophic cascades occur when predators in a food web suppress the abundance and/or alter traits (e.g., behavior) of their prey, thereby releasing the next lower trophic level from predation. In this case, the extinction of wolves caused the elk to graze freely on the aspen trees, which halted their regeneration, which subsequently impacted the entire ecosystem.
Now with the wolves back in numbers, elk behavior and vegetation distribution aren’t the only factors impacted by their return. The ripples of their recovery are reverberating throughout the entire ecosystem, in birds, fish, insects, as well as in other plants and animal species. Check out this fascinating video that explains this remarkable evolution.
Quick facts about wolves:
- 26–36 inches high at the shoulder; 4–6 feet long from nose to tail tip
- Males weigh 100–130 pounds; females weigh 80–110 pounds
- Average lifespan is about 5 years in wild; can live up to 12 years in wild
- Three color phases: gray, black, and white; gray is the most common; white is usually in the high Arctic; and black is common only in the Rockies
- Prey primarily on hoofed animals. In Yellowstone, 90% of their winter diet is elk; more deer in summer; also eat a variety of smaller mammals like beavers
- Mate in February; give birth to average of five pups in April after a gestation period of 63 days; young emerge from den at 10–14 days; pack remains at the den for 3–10 weeks unless disturbed.
CREDITS: Original video.
