Yellowstone National Park, already grappling with an invasion of nonnative lake trout, could soon see another aquatic invader, as smallmouth bass have been detected in waters not too far downstream of the park.

Despite more than two decades to get the task accomplished, and almost two years after a federal judge ordered the Federal Aviation Administration and National Park Service to get the job done by this summer, air tour management plans for eight national parks will not be completed on schedule, according to court documents filed by the two agencies.

Tegu lizards, a large invasive reptile that has turned up in Everglades National Park in Florida, can adapt to temperatures cooler than the species tolerated in its native Argentina, according to U.S. Geological Survey studies.

Grizzly bears are starting to stir in Yellowstone National Park, where one of the bruins was spotted in a meadow in the west-central part of the park.