Keep in mind I have only read this, not experienced this: Several sources have indicated that playing dead is a BAD idea with black bears, and that fighting back is the thing to do if a black bear grabs you. A black bear is much more likely than a grizzly to consider a dead human to be a food source, so playing dead is playing food. Of course, a black bear is much less likely to attack a human in the first place.
As someone already indicated, a person on a bike resembles a much larger creature, in an animal's eyes; it sees the bike and rider as one entity.
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Have Colt, will travel...