North American Black Bear - continued The black bears senses are keen with its sense of smell leading the way. No animal has more acuteness of smell. With its nose the bear finds mates, avoids humans and other bears, identifies cubs and finds food. One black bear was known to have detected human scent that was 14 hours old, while another traveled upwind 3 miles in a straight line to a dead deer carcass. There is an old American Indian saying, A pine needle fell in the forest. The eagle saw it, the deer heard it, and the bear smelled it. Bears eyesight has long been considered poor, but now new studies are revealing that it might be reasonably good. They approach objects cautiously due to nearsightedness and often stand erect to increase their sight distance, yet they are able to distinguish color and slight motion at all levels of light in day or night. Some biologists believe that bears behave like they have poor eyesight because they don't trust their vision as much as they do hearing or smell. The black bears hearing is moderately good, and it is believed that they hear in the ultrasonic range of 16-20 megahertz or even higher. One bear has detected normal human conversation at more than 325 yards and another reacted to the click of a camera shutter nearly 50 yards away. Bears possess enormous strength as evidenced by them moving rocks, moving large logs, digging huge holes and dragging or carrying large animal carcasses for miles. No animal of equal size is as powerful. A black bear can kill a moose, elk or deer with a single blow to the neck with one foreleg and then carry the carcass for great distances, however this bear is primarily an herbivore with its main source of animal protein coming from its primary prey: insects. A yearling black bear, later captured and weighed at 120 pounds, was seen turning over a flat-shaped rock, weighing over 310 pounds, with a single foreleg backhanded. The size of black bears in the wild has long been misjudged. A bear's size is usually expressed in weight, which is difficult to estimate at best, due to variations in height, thickness of fur, physical stature, as well as the nearness and stress level of the observer. During a close encounter and with an untrained eye, all bears are big, and most often much greater than the true weight. During a study in Great Smokey Mountains National Park, responses to the estimated weights of black bears were from 400 to 4000 pounds, while the actual weights ranged from 95 to 115 pounds.