I had seen them around and always been careful around them before (pretty hard to miss and easy to avoid), but my first actual fight with one actually happened inside the base of a tribe I just joined. It spawned INSIDE THE BASE.
I let it chase me into a room and locked the door behind me, only to realise that it was the same room as the tribe fabricator.
It set a bad first impression on the tribe leader and I got kicked out later on for other reasons, but yeah. Don't build your base too big or these guys could spawn in while you're at the smithy and wreck everything inside.
how to tame annoying ahh carnos that kill most dino’s and you:
1. get bow (level 10) and tranq arrows (level 21)
2. make a trap for it (u can easily find on yt)
3. find carno and shoot tranq arrows while u run to ur trap and trap it
4. shoot tranq arrows until it is unconscious.
5. feed it meat (raw meat, raw mutton, prime meat,etc)
6. boom, u got a carno.
tranq arrows are unlocked at level 21 but need narcotics (level 6) which are craftable at a Mortar and Pestle with Nacroberries (black ones) and Spoiled meat (keep any meat in ur inventory for along time to make it spoil).