This can be obtained fairly early in the game. In the extreme Northwest area of the Siwa oasis there is a small bandit camp with about five or six enemies. Dispatch them and load one of the bodies onto the back of your mount. Nearby there is a watering hole where there are some leopards. Ride your mount with the body to this area and then dismount and carry the body near one of the predators. Don’t get too close or they’ll attack you! Drop the body off and then run to a nearby bush and hide until the predator gets interested in the corpse and takes a bite – then the achievement is yours!
EDIT: While a lot of people have had success with the method described above and shown in the video, others haven't been as lucky. That said, there's also been a good number of comments offering alternative approaches that also worked. So, I've gone through the comments that everyone's left and grabbed the helpful stuff for everyone to see in one place.
If you're struggling with this achievement, try some of these tips from commenters:- You can try dropping a corpse at the vulture lair in Siwa (fast forwarding time afterward may then be necessary).
- If you get spotted / attacked you can drop a smoke bomb and run away and the predator might come back and eat the corpse.
- In Memphis, there's a crocodile that may wander around and you can leave a corpse in its path.
- You can use a sleeping dart on a predator and then drop a body on / near the snoozing creature.
- You can put a corpse on a beach (or near water), provoke a predator to attack you, then swim away into the water and the predator may then eat the corpse.
- You can place a corpse near a predator and then skip / fast forward time, perhaps several times.
- You can try shooting the corpse you placed with a regular arrow to see if that triggers the predator's interest.
Thanks to everyone for sharing what worked for you!
If you downvote, please state why in a comment so the solution can be improved.