The director of the zoo says the problem is that the female Humboldt penguins have proven too shy in their advances, adding that ”the Swedes will not make the first move.”
The females were flown in last year in a bid to bring the males to mate and help save the Humboldt species from extinction.
The initiative to ”turn” the penguins and make them mate had prompted a furious response from gay rights groups.
The zoo says it accepts ”the male couples that have formed” and that they are “not trying to enforce heterosexuality”
It did however add that they would ”be delighted if the penguins form even one heterosexual couple” and manage to produce an egg,