Grizzlies and Elk - Hayden Valley, 8/15/17

Hayden Valley in Yellowstone National Park is one of the best places to have the opportunity to view grizzly bears. The experience is enhanced even further when visitors have the opportunity to view a bear feeding on a carcass.

Grizzlies are classified as omnivore generalists, meaning anything that may have some sort of nutritional value may be part of their diet (Robbins et al. 2004). Grizzly diet in Yellowstone consists of more than 260 plant and animal species, with plants making up nearly 70% of that number. Typically, contemporary adult females and sub-adult’s diets consist 60% of plants and 40% of meat, whereas contemporary male diets consist 80% of meat and 20% of plants (C.T. Robbins, 2006).

Elk, trout and other meats that are consumed by grizzlies are approximately 90% digestible. To the contrary, plants and forbs such as dandelions and clover may only be approximately 40% digestible (Pritchard & Robbins, 1990).
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Being omnivore generalists, grizzlies seek to find and consume the most nutritious foods. Because of this, their diets do change, and shift overtime based on the abundance and availability of given food sources. Elk are an important food source to grizzly bears during in spring, early summer, and fall, even with numbers decreasing in certain areas of the park. In the Yellowstone Lake area, male grizzly bears feed on an adult elk carcass about every 4 days; females every 14 days. However, feeding on ungulates is very opportunistic, meaning grizzlies must feed on other food sources (Gunther and Renkin 1990, Barber-Meyer et al. 2008, Fortin
et al. 2013)