There's a delightful thrill to the call of a band of coyotes when you're alone in the dark woods. Do they present a danger? That is, have healthy coyotes (that is, not rabid) been known to attack or show aggressiveness to a lone human?
A few points to add here:
Coyotes are not know to be aggressive towards humans. But always remember that coyote is a wild animal. It is not domesticated and hence it's very difficult say with certainty about the behavior.
Coyotes are know to attack dogs, sheep and other livestock. So yes, they can bite. If not you, your dog maybe?
Any animal, when it loses the fear of humans, can act aggressively. This is aggravated by humans feeding the wild animals. One quick example would be the feeding of monkeys that is done in many south asian countries and in south africa. Coyotes are similar w.r.t the fact that they almost coexist with humans in urban areas now-a-days.
Hence, my advice would be, know where the boundaries are and stay well within them. It helps not only you(and possibly your dog) but also the wild life out there. And calling out to evoke a response? Well, I wouldn't really do that :P
Coyotes now live in our area in significant numbers. There was a den on our property this winter, and a few months ago there were four pups romping around in our back yard. We hear them howling pretty much every night.
I've been in the woods and in open fields with coyotes around and never felt threatened or considered it a problem at all. In fact, I think they are cool to watch, particularly the pups. Coyotes are very aware of their surroundings, and they will not let you get closer than about 50 feet. In all cases when I was closer, the coyote ran off when it saw me.
In general they are not considered dangerous because they rarely attack humans. You should not run away from coyotes as they will consider you a prey if you do. Under extreme circumstances they may circle an individual or a group. Making noise generally keeps them at bay or at a distance.
In 2009, there was, unfortunately, a fatality in Cape-Breton Nova-Scotia. This was the second recorded fatality in North America.
From Nova-Scotia website:
also according to Nova-Scotia website:
Coyotes in Eastern Canada are known to be bigger and are sometimes called coyote wolves (locally) in opposition to their smaller counterparts.