They are normally found in small packs of three, and higher level is alpha, the alpha gains a gnash attack, which is useful for taking down larger creatures over time and weaker creatures quickly, on mobile ( not sure about others) you can lower the pack down to two and it will still have the alpha in it, normally the only way to escape is getting Agro on something other than u (new tribe mate) and run u little ass cheeks off. Or taking a flying creature,
When three or more allos meet up, the highest level becomes an alpha. He will be the one with orange glowing cloud on his back. Reducing the pack to only 2 dinos will remove alpha status from the highest level allo. This means it is usually easier to kill the weakest in the pack first and then the fight will be much easier. Multiple alphas can be created if a large group of allos form. However that are not invincible. Personally saw a group of 15 Wild allos with 5 of them being alphas get wrecked by a Lvl 80 giga. So even if you could somehow tame all 15, you would be far from invincible. A good step up from a carno, but they stand no chance against similarly leveled Rex or giga.