Kelenken was a beastly carnivore, eating small to medium sized mammals that it came across. Because its beak is so large, we think that it hunted by pinning down its prey, and bashing its beak against the victim until they die. Another way it may have killed things is by picking up the helpless rodent and shaking its head so vigorously and fast that the rodent's spine breaks from the motion. They ate rodents, ground sloths, deer, horses, cows, and even armadillos! Anything that Kelenken saw would likely die.