1. You might get a more comprehensive answer at /r/heraldry .

2. Looking at this version of the arms of British Columbia, it seems that two out of three beasts are langued, or lampassé (have their tongues visible). In the province's own page on their arms, it seems that for most iterations through the past, only the lion at the crest (the top bit) has its tongue sticking out... in other words, not "all animals" are sticking out their tongues even on this coat of arms. Here's the thing...

3. Usually, with beasts of prey, a herald will want them to be kind of fearsome. They're described in a blazon as being "armed" - that is, with a certain color of claws and teeth - and will generally be snarling or roaring, depending on what it is they're supposed to be doing. The lion of British Columbia is "statant, gardant" - meaning it's standing still but facing the viewer. It's like a big watchdog, guarding the notional person wearing those arms.

According to Parker's Glossary of Heraldry, lions (especially the U.K. lion, which the British Columbia arms is meant to represent) are more usually depicted as rampant, which is to say, rearing up, as if it's pouncing on prey.

What I can't quite figure out is why that wapiti elk on British Columbia is langued at all. It's not described as such in that "Heraldry of the World" blazon (which I believe is the official one), and deer or stags are usually not depicted that way at all - see all the examples in Parker's here.

Deer are usually blazoned as "rearing" rather than "rampant" because they're considered "beasts of chase" - they don't leap onto prey, they defend themselves from leaping predators. So even up on two legs, they generally don't have their mouths open.

I'd assume it's because that elk is done in imitation of the Scottish unicorn supporting the sinister (left-hand... of the bearer, right of the viewer) side of the United Kingdom's coat of arms - except the bighorn sheep is in the unicorn's position on British Columbia's arms, and has the unicorn's tinctures (argent, armed and unguled or - meaning it's white/silver with horns and hooves of gold) ... yet the bighorn isn't langued anything. Tongue inside mouth in every depiction I could find.

Looking at some other comparable coats of arms - the old South African antelope supporters, the caribou crest of Newfoundland and Labrador, the wildebeest supporter of KwaZulu-Natal province, the red deer supporting Queensland, Australia's arms, even all those Australian kangaroos... they're all not depicted with their tongues out, even when opposite a lion.

Why British Columbia breaks with that in this most recent iteration, I'm a little stumped. Predatory elk?

There might be more wisdom to be gained from Fox-Davies' The Art of Heraldry - I can dig that off whatever shelf it's on later, if you'd like.