A group of researchers said it has found a number of same-sex pairs of penguins at aquariums and zoos around Japan.
The group, led by Keisuke Ueda, a professor of behavioral ecology at Rikkyo University in Tokyo, attributed the phenomenon to the difficulty of finding partners of the opposite sex because facilities only have an average of 20 birds, with uneven numbers of males and females.
It is not known if the frequency of homosexuality is higher than in the wild, where it it is difficult for researchers to tell the difference between genders, Ueda said.
He and other researchers, including Rikkyo University graduate student Kako Sakai, sent questionnaires to major aquariums and zoos about homosexual penguins. They found about 20 same-sex pairs at 16 facilities.
Of them, the group studied nine pairs of Adelie, Rockhopper and Humboldt penguins -- five female pairs and four male pairs -- by videotaping their behavior in breeding seasons.
Seven of the nine pairs were found to have shared their nests like heterosexual pairs, the group said.
