Hard to believe, but all of the following thoughts can pass through the human brain faster than you can say, "Oh, s---!" What is that bear doing in the middle of the trail? ... Is this friggin' grizzly deaf or just stupid? ... Get your butt back over the rear tire and get on the brakes ... Let's hope this doesn't turn into a Petra mess.

Petra, for those who don't know, would be then-15-year-old, Anchorage mountain biker Petra Davis. She was nearly killed by a grizzly in June 2008, but fortunately is now all recovered and back on the bike. No one knows exactly what preceded her night-time mauling during a 24-hour mountain-bike race at Hillside Park, but there are some who believe it quite possible Davis smacked into the bear on a trail near salmon-filled Campbell Creek.

Having nearly hit bears on a couple of occasions -- the latest being several days ago -- this is easy enough for me to believe.

The most surprising thing is that mountain bikers and bears in Alaska don't collide more often. Alaska has a lot of riders, a lot of bears, and a lot of places they could meet, which is almost anywhere. All of Anchorage is bear habitat. Don't be fooled by the idea that because the Rover's Run Trail in Far North Bicentennial Park is supposedly closed to protect you from bears that you won't meet one elsewhere. Likely you won't, but you could.

In most cases, the lack of biker-bear encounters is no doubt due to the bears being alert to the bikers, who generally tend to be pretty noisy. You could, however, run into an inattentive bear, or one that just doesn't care that much about people. Bears don't text while driving, but they can sometimes be inattentive to the world around them anyway.

In my own most recent case, noise didn't serve to warn the bear for some reason. As usual, when I started a fast descent down an old road through the alders above Paradise Valley on the Anchorage Hillside, I was singing "Dancing in the Rain'' at the top of my lungs. Anyone who has heard me sing knows how awful this sounds. Tone-deaf does not begin to adequately describe the horror of this singing. Normally, it can be counted on make the bears run for the hills. On one occasion, I actually saw a bear break out of the grass and tear off down a trail when I started signing.

Why the bear the other day didn't didn't flee is hard to say. The wind was blowing pretty good, and that might have covered some of the sound; although, I was singing even louder than normal because of the breeze. Maybe this was just the case of a bear, which appeared to be young, being relatively inexperienced with life among the people of Anchorage.

Alaska Department of Fish and Game studies have, in recent years, documented a significant number of grizzlies using Anchorage as part of their home range. Given how seldom people see these bears, which radio-collars tracked through every green area in the city with some regularity, it is clear the animals have become adept at avoiding people.

The bears of Anchorage truly do not seem to want trouble with the people of Anchorage unless, of course, maybe you collide with one. Colliding with a black bear might not be such a bad thing. That happens with some regularity all across North America now because the continent has a large number of black bears. The black bears hit by cyclists almost always run off. But I wouldn't want to count on this with a grizzly -- the black bear's bigger, more aggressive cousin.

Grizzlies aren't genetically programmed to flee the same as black bears. They judge the flee-or-fight choice differently, and just might be more inclined to rough you up a little. It is a good idea to have top-flight brakes on your mountain bike in Alaska.

Mine are good enough that the main worry is going over the front of the bike when in a panic stop on a steep downhill. Thus the thought about getting back behind the saddles, which is what I was doing as the bike was skidding to a stop and the bear was getting that "whatinthehell'' look on its face.