Use gillie armor!

Tamed 2 ( lvl 125 and lvl 90 ) did some upgrading mostly to health and melee. Turned my back to cook some meat. Hear scary music, see lvl 130 Rex's corps just flying over my head.

No gille armor all you need to do is crouch behind it and shove berries up its butt...I'm not kidding

They don't have this listed on here I don't know why, but they collect 2 x more of plant x seeds than than any anamal I have found.

Do not try to knock out these guys there a passive tame so in other words put berrys in your last slot I your hot bar and keep your distance and leave about 2-3 minutia beer seen each visit to it