In 1995 the Grey Wolf was re-introduced into the Greater Yellowstone Ecosystem with 14 pair being released. Since that time its numbers have been growing steadily. It is a predatory animal that provides carrion for other animals within the ecosystem. Human hunters also provide this service within this ecosystem.

Recent research by scientists from Berkeley and Yellowstone has been analysing the differing nature of carrion provided from these two sources. Human hunters provide carrion predominately for bald eagles and ravens. Wolves on the other hand provided carrion for a far more diverse group of scavengers.

The wolves are making a positive contribution to the biodiversity of this ecosystem but they are not out of the woods yet. (excuse pun) Elements of the relationship between the ungulate population of the park and the wolves are currently dysfunctional arising from the absence of wolves and bears from the park for over 75 years. The Wildlife Conservation Society reports that Moose are failing to acknowledge the presence of large predators in their environment.

It has taken 10-15 generations for moose to loose their wariness of large predators but it may only take one generation for them to regain it. The WCS reports that

Wyoming moose that have lost even one of their offspring to predators may become as savvy as their Alaskan cousins within a single generation, which indicates that mechanisms for predator avoidance are already in place