Lake and MIB: Don't discount the probability that they fall back on human resources and/or refuse for food as needed, especially in areas where the climate may result in hardship with regard to standard prey, etc. Also keep in mind that prey animals often live in fringe habitat such as tree lines and intermittent wooded areas in suburbs and industrial areas, usually for the same reasons - they are living off of habitat we create and things we leave out or throw away.
Branco: In Lemmon Valley, Nevada it is arid high desert with limited water sources. Even so, the valley was apparently a migration route from the area around Lake Tahoe, traveling North by Northeast, skirting the Northwestern edge of Pyramid Lake (a living salt lake with fish and other wildlife), and passing through the Pah-Rum Mountain Cluster, then on up to Southern Idaho.
Our community had a water tower tucked back between two fingers on the large Eastern ridge of the Valley. There was a large pool, much like that of a spring at the base of the water tower, along with some succulent vegetation. It was the only source of clean, fresh water within a couple of miles. As a result, at least one family group would stop in our area for a while each summer. The water brought them into contact with us.