DRAPER, Utah (ABC4 News) –If you want to impress a loved one, you might try flowers, candy, or a nice card. Penguins show their affection by searching for the perfect stone to give their mate.

Each year on Valentine’s Day the Living Planet Aquarium loads smooth stones into the penguin’s habitat to begin mating season.

The Gentoo penguins spend weeks searching for just the right rock. The male presents the stone to his mate, and if she accepts it, they add it to their nest.

Many Gentoo penguins at the aquarium have mated with the same partner year after year.

Last year the aquarium conducted the first-ever Gentoo penguin paternity study in partnership with Utah Valley University.

The study showed that if two penguins were raising a chick together that didn’t mean the pair were the chick’s parents.

According to the study, a penguin named Roto was the biological father of five out of eight chicks tested at the time. Roto’s partner is Copper, with whom he raised three chicks, but he also mated with Coco. Coco raised two chicks with Gossamer, her partner.