To knockout or kill the Doedicurus shoot him in the head and walk Backwaren White reloading and continue to shoot it in the head. If you do so it wont be able to Hit you. If it flees slowly follow it and am for it legt or tall.
There’s a big open area near green obelisk, redwoods and swamp. If you are lucky you’ll find one. Beware though, spinos, rexes, raptors, carnos, barys, and theris are all relatively common around here. I’d recommend a good flyer or bruiser of your own if venturing here. Flak also helps.
You can find them in the redwoods, by obsidian mountain, and north of the beaver spawn near hunter cave. I highly advise using an Argentavis so you can just pick it up and knock it out in a safer spot.