A bear that demonstrates defensive behaviour is a bear that is feeling stressed or threatened. A stressed bear commonly displays a change in:
body posture;
vocalization, such as teeth popping, blowing and huffing; and
body movements, including subtle ones such as ears going back, swatting at the ground or swaying the head, or even a charge.
In most cases, other clues will also be present, for instance, the presence of cubs or a carcass.
It is not uncommon for a bear to bluff charge in an attempt to remove a threat. A bear may bluff charge to within a few metres or run past the person with no intention of attacking. Any close encounter with a bear can be frightening, but it is important that people not panic and do not react in a manner that might escalate the situation.