Most guarders will be presented as behaving aggressively to family members rather than strangers. Although many resources guarders will guard from just about anybody who is around. family members are more likely to be around enough to come across the behavior. Sometimes the owner will identify that the issue is the dog's control of or proximity to a certain resource, but other times will not know why the dog is being aggressive. It may even appear to a bewildered owner to be completely unpredictable. This is especially likely when there is a hidden combo, or when the resource or body part has simply not been recognized as being "hot".