What eats hermit crabs?

Answer 1

bigger ocean animals like dolphins and sharks and whales all  kinds of whales

Answer 2

Sometimes larger crabs

Answer 3

Seagulls and other shore birds, turtles, and large rodents. Other hermit crabs of the same species or different ones may even eat each other. Im not sure if they do this for nutrition or to get a larger shell, but either way they attack each-other. Also large fish.