How does Captain Hook know when the crocodile is near in Peter Pan?

Captain Hook knows that the crocodile is near because he can hear it ticking. The crocodile has a clock in its stomach, so when it approaches him, Hook can hear a loud ticking sound, which tells him that it's time to head off quickly in the opposite direction.
Once upon a time, Peter Pan cut off Captain Hook's arm and fed it to the crocodile. Now the crocodile wants to finish what was started, so he vigorously pursues the bad Captain in search of a snack. As long as the crocodile still has a clock ticking away inside his belly, however, Captain Hook should be able to avoid him. But if, for whatever reason, the clock falls silent, then Hook will be in very serious trouble indeed.