What to do when you've crossed paths with a bear? To avoid running into any problems of the Goldilocks variety, here are three safety tips for three different bears: The American brown bear, the American Black bear, and the Polar bear.

Brown bears

Attacks by North American grizzly bears have been rising in the U.S., due partly to growing grizzly and human populations, and partly to food shortages that some scientists blame on global warming. But climate change may also expand grizzlies' range, possibly even into polar bear habitat.

If you encounter a brown bear, keep these tips in mind:

Don't run. If you do meet a grizzly, stand tall, stay calm and slowly reach for your bear spray. Don't worry if the bear stands up — that usually just means it's curious. Back away slowly if you can, still ready to spray. If the bear follows you, stop and stand your ground.

Play dead. Even if the bear starts to attack, it's likely trying to neutralize you as a threat. And since you'll never outrun or overpower it, faking death is your best bet at this point. Even if it walks away, don't get up. Grizzlies are known to linger and make sure you're dead, so stay down for at least 20 minutes.

Box its nose or eyes. This could feasibly thwart a grizzly attack, but only fight back as a last resort. Playing dead is the preferred strategy with grizzlies. If you can get free, though, back away slowly; still don't run.

Black bears

American black bears occasionally attack humans, but since they're smaller, faster and better climbers than grizzlies, they'd usually rather flee than fight. Asiatic black bears, on the other hand, are more prone to attack people, a problem scientists say could worsen with climate change.

If you encounter a black bear, keep these tips in mind:

Stand your ground. Black bears are less aggressive than grizzlies, so as long as you demonstrate yourself to be large and loud, they'll usually leave you alone. Shout, wave your arms and create a commotion. Use sticks or other objects to make yourself look even bigger. And just like with grizzlies, never run from a black bear. They often bluff charges, and the best strategy is to stay in place with bear spray ready to fire if the bear gets too close.

Stay on the ground. Never climb a tree to escape a black bear. They're excellent climbers, and they tend to chase anything they think is running away, so there's a good chance it would trap you in the tree.

Fight back. Unless you're physically unable, it's often better to defend yourself against a black bear than to curl up on the ground. Keep making noise and looking large throughout the encounter, but if you end up at close range, use any nearby object as a weapon to fend off the bear. If nothing useful is around, punch or kick the bear's nose. Do whatever is needed to scare it away, but focus on sensitive areas that are likely to get an immediate reaction. Try to create space between you and the bear, but never run away — make the bear do that.

Polar bears

Humans are no match for any bear one-on-one, but with polar bears the contest is especially lopsided. They're also less accustomed to seeing people, and are more likely to see us as prey.

If you encounter a polar bear, keep these tips in mind:

Good luck. Polar bears are the biggest bears on Earth, and they're much harder to scare than brown or black bears. The best strategy is to avoid meeting them in the first place.

Don't act like prey. This is good advice for any bear encounter, but especially so with polar bears. They're the most likely species to see you as a meal, and running away will only confirm their suspicions. Plus, they're faster than you, and much better at running on snow and ice.

Don't give up. Unfortunately, neither playing dead nor fighting back works as well against polar bears as against their smaller relatives. They're often more interested in eating you than in neutralizing you as a threat, so playing dead might just make their job easier. Fighting back is pretty useless, too, but if you find yourself rolling around the tundra with a one-ton polar bear, you don't have much to lose. As with other bears, try to injure its nose or eyes, and steer clear of those big, swinging paws. A single strike can kill a person.

So before you walk off into bear territory, make sure you're prepared enough to handle any surprises along the way. For more information on bear attacks, including what to do to defend yourself against other bear species, check out Mother Nature Network.