Where: I've found quite a few in the red woods at the base of metal mountain. You just have to look they are easy to miss.

What: you'll need some mushrooms for taming food and some narcotics bring the quantity accordingly.

When: morning is easiest to spot them. Any closer to night and they can dissappear pretty quick if you don't get them down right away.

How: you can build a 1 by 1 structure around them to keep them in place, corner them in the rocks in the mountains or (like I did) use a scorpion to stop them in thier tracks (easiest way for fast dinos since I don't really build traps).

These guys seem to be delicious because every predator wants them so be sure to protect. (Usually keep a couple dinos to call in for sentry duty)

Enjoy your tame!