If you find a good sarco to tame in the swamp, you can build a cage on a raft and lure it in. After you've cought it just drive the raft out of the area and go tranq it somewhere safe.

It takes a while for the torpor to drop so, I'd say tranq it and then go get some prime fish meat from some sabertooth salmon.

The amount would will depend on your server settings. After you got the meat the sarcos hunger should be down by alot so you might end up instant taming it.

Normal fish meat will work too but the taming affectiveness will take a hit.

If your having trouble getting enought prime, you can also put in all the prime you have and then fish meat just to get a few more levels.