Toto and Poko, a toucan couple at the Maruyama zoo in the northern Japanese city of Sapporo, have been sharing a home since 2013. After reaching sexual maturity in 2016, the birds were expected to reproduce. Every year, zookeepers would discover two or three eggs in their cage, but none have hatched.
To encourage reproduction, the puzzled zookeepers played the part of the mood maker. They built them bigger nests and changed their diets, but still no chicks. In fact, the zoo staff never once saw the birds mount each other, although they assumed they could have done it while no one was watching.
It wasn’t until 2020 that the zookeepers decided to run a DNA test on the toucans. Earlier this month, the zoo announced that Toto, the bigger toucan and what was assumed to be the male, was a female like Poko.
“When we first bought them in 2013, we were told it was one male and one female,” Hideaki Yamamoto, the exhibition breeding manager of the zoo, told VICE World News.
“It’s difficult to determine their sex from their physical characteristics, so we didn’t know,” he said.
To confuse matters further, the toucans exhibited courtship behavior, which is usually seen between mating partners.
“Toto would give Poko food. And if Poko flew out of the nest, Toto would follow to be closer to her,” Yamamoto said. “We now know that same-sex birds can exhibit those acts too.”
Same-sex courtship behavior, which can include dances, gift-giving, or showing specific body parts, has been documented in over 130 bird species. It’s raised questions among scientists about the purpose of these acts: If it doesn’t help produce offspring, why bother with all the song and dance?
But research by scholars such as Geoff MacFarlane, a biologist at Australia’s University of Newcastle, shows that birds may engage in homosexual behavior, or even gay sex, simply because they can.
In a study of over 93 bird species, MacFarlane noticed that whichever sex had less parental responsibilities, they’d typically engage in more homosexual behavior. More time on their hands meant more freedom to be sexually explorative, which, in MacFarlane’s study, males in polygynous species indulged in.
Birds aren’t the only animals to engage in homosexual sex.
Female homosexual behavior among Japanese macaques, a genus of Old World monkeys, has been well-documented. Some scientists have even identified male macaques competing with females for female sexual partners.
At the Maruyama zoo, Yamamoto hopes to increase the number of toucans and is considering adding a male to the mix. When that day comes, the zoo will find out if Toto and Poko are as inseparable as they seem.