Moose are the biggest deer in the world, and their incredible bulk can be startling if appreciated up close. But such up-close appreciation is not at all advisable.

A couple of recent videos out of the U.S. show some harrowingly close encounters with these towering ungulates, though thankfully both human and moose ended up unscathed in the two incidents.

In one, a 12-year-old mountain biker filming his ride in the Government Peak Recreation Area in southern Alaska’s Talkeetna Mountains nearly collided with a cow moose that suddenly dashed across the trail:

And in the other, thousands of miles away in the Southern Rocky Mountains of Colorado, a person had a bit of an edgier interaction with a bull moose. Colorado Parks and Wildlife posted the footage to social media last month as a warning:

“The individual just by chance came upon the bull walking along a willow bottom heading towards a lake,” the state wildlife agency noted. The resulting footage shows the person filming in risky proximity to the moose, which was sporting a hefty pair of antlers still in summer velvet. The bull sways, tips, and lowers its huge head before abruptly charging the person at close quarters. Fortunately, a tree in between the two parties shielded the person from what could have been a big-time clobbering.

Moose evolved in Eurasia (where they're more widely called “elk”) and colonised North America with the retreat of Pleistocene continental glaciers. They are ungainly-looking beasts: humped, swollen-nosed, and perched on magnificently stilt-like legs. If the oversized deer are observed knee-deep in a beaver pond or wading through a lake scarfing aquatic greens, they may give off a sluggish, mild-mannered vibe.

Nothing could be further from the truth, really. Moose are notoriously volatile browsers that can turn into terrifying defensive assailants on a dime. More people are injured by them in Alaska every year than by bears.

This aggression is a survival strategy. Moose often use those stalk legs of theirs to outpace their primary North American predator, the grey wolf; they can canter right through brush, deadfall, and snowdrifts that slow down pursuing wolves. But sometimes flight isn’t as ready an option. In deep snowpack, or in the spring and early summer when a cow tends to a single calf that's vulnerable not only to wolves but also black and grizzly bears, moose may instead need to stand their ground and meet a potential predator face-to-face.

Head lowered, ears flattened, mane bristling, and both front and hind hooves kicking out, a moose defending itself or its young is something to behold. The late Valerius Geist, a noted authority on ungulates, wrote in his Deer of the World: “Because in winter moose must stand and fight predators, their threat [to humans] is carnivorelike. The harsh roar of a confronted moose is bone chilling; an attacking moose is a thoroughly frightening sight.”

While a cow defending her calf is the most nightmarish version of Moose-in-Beast-Mode, any moose whose personal space is violated may attack. Given the animals aren’t at all opposed to wandering through towns and suburbs (ala those classic Northern Exposure title credits), that personal space may include sidewalks and backyards.

Read more: Watch this moose take his frustrations out on a car (and a mailbox)

And this time of year we’re beginning to slide into the season of the rut, when bull moose keen on cows – and on besting rivals – become especially unpredictable and cantankerous. (Two bull moose going at it in the fall – which, among well-matched contestants, can get plenty violent – is another sobering demonstration of the animal’s power and pugnaciousness.)

Dogs can also, unsurprisingly, set off a moose, to which they surely appear as less-classy, more-boneheaded wolves. Hiking with unleashed dogs in moose country is a risky proposition, not least because you may find your pooch fleeing to your protection with something giant and angry close in pursuit. (Moose riled up by dogteams are notorious challenges on the famous Iditarod sled-dog race.)

Given moose aren’t inherently bloodthirsty – they’d just as soon go their way and let you go yours – avoiding unpleasant run-ins is (outside of nighttime mushing through the Alaskan bush) usually pretty straightforward. So let’s wrap up with a little Moose Safety 101, distilled from the highly moose-aware Alaska Department of Fish & Game.

Enjoy and photograph moose from afar. If you encounter one on or near a trail, back away slowly to a safe distance. Watch closely for signs of moose annoyance or apprehension, including raised hackles, lowered ears, and snout-licking.

As with grizzly bears, most moose charges are bluffs. But do you really want to play the odds? Unlike with bears, the best course of action if charged by a moose is simple and instinctive: run the heck away! Moose rarely chase people very far, and though they’re impressively fast you’ve got a good chance of out-manoeuvring one. Get something big and solid in between you and the moose as quickly as possible.

In the event a moose does get to you before you're able to flee, get on the ground (you may not have a choice) and curl into a ball, protecting your head. Try not to move. After a few kicks or stomps, the animal’s likely to break things off; stay motionless until it moves out of the vicinity. Getting up prematurely may invite another defensive attack.

For more information on keeping the peace with the heavyweight champ of the deer clan, check out this Colorado Parks & Wildlife video:

Top header image: Nate Hughes Flickr