Hoary Marmots are common in the subalpine regions in the park, where they eat vast amounts of meadow vegetation. The thick layers of fat they develop allows them to survive eight to nine months of hibernation each year. Hoary Marmots are named for the grizzled grey fur on their shoulders and upper back, which fades to brown on the lower back. The tail is dark brown; the head grey with a black band across the bridge of the nose, and white patches on the nose. Marmots are sometimes called 'Whistlers' for the shrill whistle call they can make to warn against the presence of potential predators.