Gay penguins Stan and Olli moved to male-only enclosure

Penguins aren't the only animals known to form same-sex relationships – but they are perhaps the most well-known (and adorable).

King penguin couple Stan and Olli are moving to an all-male enclosure in Hamburg while also becoming a symbol for marriage equality campaign in Germany.

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Stan and Olli were brought to Berlin Zoo as part of its breeding programme, but they chose each other as mates.

The penguins will be joining Humboldt penguin couple Juan and Carlos in Hamburg.

It turns out that gay penguin couples are quite common and some become parents too.

Silo and Roy of Central Park Zoo New York inspired a children's book when they successfully incubated a donated egg.

The pair's six year relationship ended when Silo left Roy for a female called Scrappy, suggesting that there are also bi-sexual penguins.

Long-term couples like Stan and Olli are especially symbolic in Germany where human same-sex couples still cannot marry and face strict barriers when it comes to adoption.