At the top of the food chain is the tertiary consumer. They are the carnivores that eat the carnivores. Often, they do not have predators. Humans fall into this category, but so do many other large animals such as lions, bears, and sharks. There are times of course, where a tertiary consumer does fall victim to another predator.
As you can see from our food chain, one consumer can be eaten by another. Food chains only tend to be short if the primary consumer is a very large animal with few predators. Large herbivores such as moose, elephants, bison, or giraffes have few predators because they are so large and powerful. Their food chains are short. But what happens to the energy stored in their large bodies when they die? Enter the scavengers and decomposers!