Mates for life

Amazing fact, the male penguin when he is ready to have a mate, searches the whole beach over for a perfect pebble. When he finds what he thinks is the perfect pebble, he lays it down at the feet of a female penguin he wants as a mate for the rest of his life. If she picks up the pebble, that's it, they are literally mates for life as long as they live, they never seek another partner.