Tame them by getting their eggs. Use a whip while you're grappled to a flyer. They need five fireplaces to hatch. It doesn't take that long for them to grow, but to hatch them it's thirty minutes. They can be found easily on the white cliffs along with their eggs. I don't care if you like this or not I just wanna give tips.
I use anywhere from 15-20 standing torches to hatch their eggs. Works like a charm. As for stealing eggs, I usually use a pteranodon. I like to lure some of the adults away first, by flying close to the ground for a bit and then striaght up once they're far away, then I grab any eggs I see. Honestly easy enough and they're amazing tames.
Once an alpha has been appointed by having 2 or more Deinonychus together, the Roar ability will be usable.
Using the Roar ability will cause the alpha to do a screeching roar which is imitated by the other Deinonychus, giving them 50% increased damage as well as reducing the damage they take to around 60% instead of the full amount of damage delivered.