The team in Denali uses GPS collars to track the wolves’ locations, which update every four hours to maintain battery life. Among many other things like tracking hunting patterns, the data from the collars can tell the biologists when its safe to go retrieve footage from their cameras inside the wolf dens. Housed inside tough weatherproof casings, the cameras have motion and heat sensors so they know when to take pictures of the wolves in their natural habitat.
The Greater Yellowstone Ecosystem learned the hard way just how key wolves are when they were eradicated in the 1920s. The entire ecosystem was thrown off balance, and not in a good way, and is only now beginning to recover since wolves were reintroduced in the 1990s. The efforts of the NPS in Denali and other places are important to preventing this from happening again.