Do you have a wyvern if so land in the mid desert and walk around you will see them move to you and bring them to where you have your dinos or use a good wyvern to take them out
Same when i was on SE, would take a rex and zig-zag though the desert from green to blue until one popped, you could do it with wyvs but I always used mine to look for alphas at night or If i just got lucky lol
Careful trapping or penning them to tame, mine always got ticked off at my gate frames on the last bite. By the time it calmed down tame had reset, a few times I just had to kill it