If a person walking in the woods sees a large, hairy bipedal creature, he or she is likely to assume it's Bigfoot. But Bigfoot is of course not the only large hairy animal that can stand on two legs; bears, for example, can stand and even briefly walk on two legs, as can chimpanzees, bonobos, baboons and other animals.
Other large animals such as moose or elk, when seen from behind and/or in near-darkness, can also appear to be standing on two legs and therefore Bigfoot-like.
In these cases the reason that an eyewitness rules out a known animal in favor of an unknown one is that he or she assumes that there are no wild animals in the area that could look like that. Clearly, that is not always the case.
As wild animals lose more and more of their native habitats they are drawn closer to cities and towns. Coyotes and bears, for example, have become an increasingly common sighting in many areas. And that's only the tip of the iceberg.
Exotic Animal Escapes
In 2010, two camels and a tiger were found in the woods in Canada. The animals were among several being moved from Nova Scotia to a private zoo outside of Toronto, and they escaped when the truck carrying them was stolen by thieves in Quebec.