Although generally slow-moving and sedentary, moose can become aggressive and move surprisingly quickly if angered or startled.
Moose are not usually aggressive towards humans, but can be provoked or frightened to behave with aggression. In terms of raw numbers, they attack more people than bears and wolves combined, but usually with only minor consequences. In the Americas, moose injure more people than any other wild mammal and, worldwide, only hippopotamuses injure more.
Like any wild animal, moose are unpredictable and should be given a respectful amount of space. They are most likely to attack if annoyed or harassed, or if their "personal space" has been encroached upon. Moose that have been harassed may vent their anger on unwary victims, and often do not make distinctions between their tormentors and innocent passers-by.
However, moose often give warning signs prior to attacking, displaying their aggression by means of body language. The maintaining of eye contact is usually the first sign of aggression, while laid-back ears or a lowered head is a definite sign of agitation.