A pen does help taming Equus and can keep them from running into unsafe areas while you do, but you need to give them time in the game to calm down from being either dropped by a flyer or pulled by a lasso into the pen.
Once the Equus is in the pen leave it alone for an in-game day. Keep your tames and yourself away from the pen. Once it calms down, go in and tame like you normally tame an Equus.
I am having a very hard time taming a Raptor right now because when I bolla it as soon as I hit or shoot it it escapes the bola and attacks me normally killing me even when it has ten bolas around it’s legs so The only way I am able to tame it is by standing on rocks and shooting at it from there . I am playing on an island by myself at the easy level if that helps.
I dare you to raise one!! They are savage if you got two high lvl parents (about lvl 140ish) and you get imprinting on it. The thing will become an adult with about 230% melee and basically one chomp any bronto!!! But on the down side you loose your job and your girlfriend
I found a level 16 for my pursuit to tame one. 2 Galli kibble and 10 (probably overkill) did the trick, took 2-3 minutes. 2-3 tranq darts will knock it out easily, just wait a second or two inbetween shots. Best wood gatherer, do not listen to anyone else. Also I've heard it can be a mobile smithy.