Pagurus filholi is a hermit crab species that lives on rocky shores all over Japan. Unlike land hermit crabs, they spend their entire life in the water. A male hermit crab grabs the shell of a female and carries it around for a few
days before mating (see photo). The guarding male will flee or fight against other males who challenge him for the female. They also show bun-bun behavior, in which the male grabs the female and shakes her vigorously. The reason why the male shows
this behavior is still unclear. The video shows how to identify hermit crab species in Hakodate Bay, guarding behavior, and bun-bun behavior.