The largest part of the Sierran black bears diet is vegetation. Meadow plants, grasses and tender herbs are the most important food source before the berries and nuts ripen in late summer. Seeds, nuts and berries are the second most heavily consumed bear foods. Manzanita berries and acorns are major components in a bears diet. Autumn’s acorns are critical to the bears’ desperate effort to gain weight needed to survive the coming winter. Sometimes in the fall, bears are acorn crop plentiful, some bears may remain active, spotted shaking down acorns from the oak trees. If the winter is warm and the descending from the conifer forest to the oaks below. Insects are the most important kind of animal food and bears in the Sierra regularly tear apart logs for carpenter ants and dig up yellow jacket nests. Black bears eat relatively little meat, occasionally killing deer or eating the carrion left over by other predators such as cougars.