Kupela eggs can move themselves with their small tails. To hatch, they are stored in wet barrels without sunlight aboard pirate ships. (No Kupela has hatched in any other conditions on the island of Ark.) You can hatch one in Ark Bay if you happen to have a barrel from a pirate ship though.
Kupelas first hatch in the wet barrel in which the egg was placed. Their first major challenge is to gnaw their way through the wood of the barrel to escape the tiny prison. Some Kupelas are weak or lose their teeth from so much gnawing before they make it all the way through and, as a result, die.
Kupelas who are lucky enough to escape their barrels find other places on the pirate ship to live. They snack off the crumbs of the sailors and food that's stored on the ship.
Sadly, Kupelas and sailors don't normally get along because Kupelas are very aggressive and often hassle sailors in their vicinity.