Their eyesight is fair, but they have great senses of smell and hearing. They can run up to 35 miles per hour, are great tree climbers and can also swim. Sometimes they will stand up on their hind legs or come closer to get a better look. This is not necessarily a sign of aggression.
If food is not available, bears do not have to eat, urinate or defecate all winter long and can simply sleep through the winter. Some scientists call this winter denning, others call it hibernation. Bears differ from groundhogs, squirrels and other hibernators in that they do not have to wake up to eat and excrete waste. When bears come out in the spring, they are very hungry and most of our bear encounters happen during the spring and summer. Typically, by fall, there is enough natural food available for bears, like nuts and acorns, decreasing their need to roam into towns and neighborhoods in search of food.