 Conversely, Yellowstone x rainbow crosses are common; the "cutbows" of Yellowstone Park in the Lamar River drainage are natural hybrids.In addition to their natural aversion to cross-breeding with other trout, fine-spotted cutthroats are unusual in their pursuit of a vertebrate diet, mainly other fish, but occasionally including small mammals.They are the only river cutthroat with a vertebrate diet, and as a result their territorial waters are almost devoid of whitefish.