It is said that when lemmings breed to a state of overpopulation they commit collective suicide by pouring over cliffs into the ocean, while dolphins and whales have been known to end their lives by deliberately stranding themselves in the shallows.
據說，鼴鼠在繁殖過剩時，會集體跳海自殺；海豚、鯨魚則成群遊到岸邊「擱淺」自殺。