Not. Grizzlies aren't invasive here. A species is invasive basically if: 1) has been introduced directly or indirectly by man actions (a mosquito carried on a

Not. Grizzlies aren't invasive here. A species is invasive basically if: 1) has been introduced directly or indirectly by man actions (a mosquito carried on a plane, a lost exotic pet). If arrived by its own means is not invasive. 2) is not a previous part of that ecosystem so it didn't evolved here; There are exceptions to this rule [1][2] 3) is reproducing in the new area (often explosively by lack of predators and diseases), also with some exceptions [3]; and 4) Will modify the ecosystem substantially (displacing or wiping other species in the process). Wolves on Yellowstone fulfill all points except 2. They aren't invasive. Apples on America don't fulfill points 2 and 4 so they are more healers than destroyers, and reproduce but not exponentially. ------------ [1] Can be ignored when the new species fill a niche from an extinct one, "Healing" the ecosystem. Gray wolves proven to be solid healers for example. Turkeys on Mauritius island could be the only birds able to spread the seeds of some trees unable to reproduce since Dodo went extinct. In this case we can do an exception to save dozens of native species from going extinct. [2] Creating deliberately a sanctuary of a non native species to reduce the risk of being extinct in their own place, is also allowed. [3] neutered domestic cats, gone feral, are invasive, because there is still a constant supply from other areas.