They say the way to a man's heart is through his stomach. For Gentoo penguins, a pebble or two might just do the trick.
Buster and 99 are a couple of penguins that have shared pebbles for 24 nesting seasons – that's a decade in human years - raising 19 chicks along the way.
Their romance can be put down to compatibility and hard work says Penguin Keeper Kristen Buckley.
"Biologically speaking, it is crucial that penguins make sure they are with a good partner," Buckley says. "They can't afford to have a partner that isn't very good at catching food or finding nesting material because this means that their chicks are very unlikely to make it to adulthood."