Darwin believed that animals only mated to reproduce, but scientific evidence suggests this is far from true.

Eastern Daily Press: A team of common dolphins patrol the coastal waters off South Africa's Cape in search of sardine shoals. Photographer: BBC NHU, for Africa.A team of common dolphins patrol the coastal waters off South Africa's Cape in search of sardine shoals. Photographer: BBC NHU, for Africa. (Image: WARNING: Use of this copyright image is subject to the terms of use of BBC Pictures' Digital Picture Service (BBC Pictures) a...)

A UEA academic has suggested wildlife programmes don't represent the full sexual spectrum of the animal kingdom. Stacia Briggs finds out if it's time for nature shows to come out of the closet.

Eastern Daily Press: Shows: Black Rhino silhouette at sunset, Hluhluwe-Imfolozi Reserve, South Africa. Photo: Jed Bird, for Natural World.Shows: Black Rhino silhouette at sunset, Hluhluwe-Imfolozi Reserve, South Africa. Photo: Jed Bird, for Natural World. (Image: WARNING: Use of this copyright image is subject to the terms of use of BBC Pictures' Digital Picture Service (BBC Pictures) a...)

It's the love that dare not squeak its name – new research from an academic at the University of East Anglia suggests that BBC wildlife programmes may be 'too heterosexual'.

A study by Dr Brett Mills published in the European Journal of Cultural Studies puts forward the theory that filmmakers fail to offer alternative views of animal behaviour and instead concentrate on reflecting human 'norms' of sexuality and family.

After examining BBC programmes including The Life of Mammals, The Life of Birds and Life in the Freezer, Dr Mills suggests that certain forms of animal behaviour are commonly missing in wildlife shows and that viewers are not being offered the full picture.

'I think that the issue of showing that homosexuality in the animal kingdom is present and is in fact completely normal is quite a threatening concept to some people,' he said.

'Presenting programmes that concentrate only on heterosexual animals perpetuates the belief some people have that being gay isn't 'normal' and that this is proven by the animal kingdom.

'In fact, there's a great deal of evidence to suggest that homosexuality in the animal kingdom is perfectly normal, yet documentaries offer a single interpretation which presents a mismatch between what we see on screen and what science tells us.'

There is well-documented evidence of homosexual and bisexual behaviour in the animal kingdom which includes sex, courtship, affection and parenting among same-sex animal partnerships.

Researcher Bruce Bagemihl put forward evidence which revealed that such behaviour has been observed in around 1,500 different species ranging from gut worms to primates.

'The animal kingdom does it with much greater sexual diversity than the scientific community and society at large have previously been willing to accept,' he said.

Roy and Silo, two chinstrap penguins at the Central Park Zoo in Manhattan, had a devoted same-sex relationship for six years which involved raising a chick together while studies show that 10 to 15pc of western gulls enjoy same-sex partnerships.

Other animal species that have been observed in non-heterosexual relationships include male and female bottle-nose dolphins, monkeys, sheep, reptiles, koalas, giraffes, butterflies, octopuses, molluscs and insects (male dung flies, for example, appear to mate with other males with the aim of exhausting them and reducing the competition for females).

It was, in fact, Roy and Silo's gay penguin romance that inspired Dr Mills, a senior lecturer and head of the School of Film, Television and Media Studies at UEA, to investigate the way wildlife documentaries approach the issue of homosexuality and same-sex parenting in programming.

'I read about the gay penguins and thought to myself 'I wonder if this is a common thing?'' he said.

'A book was written about Roy, Silo and the baby they raised, Tango, and it became the most banned book in America, which shows you how controversial a topic this can be.

'People look to the animal kingdom to provide them with answers about what it means to be human and it raises the question of whether homosexuality is a choice or a result of nature.'

Dr Mills believes that wildlife documentaries could be useful in a wider debate about sexuality and the way modern families are evolving.

'You only have to look back a few decades to a time when homosexuality was illegal.

'People were still outraged in the 1990s when Brookside showed its first gay kiss and only this week there has been a huge furore over the gay marriage issue,' he said.

'Wildlife documentaries have a story to tell and they tend to tell the easiest story.

'You wouldn't see a documentary about humans that assumed that everyone was heterosexual, but with animals it's easier to tell the stories of families: a father, a mother, offspring – even if it doesn't tell the whole story.

'It's very common for swans to raise cygnets in same-sex couples and if they do, the cygnets are statistically more likely to survive: two male swans can protect their offspring better than a male and a female.'

Channel 4 broadcast a documentary, The Truth About Gay Animals, in 2002 which was described by then-director of programmes Tim Gardam as 'amusing and quite sweet' and was presented by an American comedian, Scott Capuro.

But Dr Mills said that documentaries which showed the full spectrum of sexuality in the animal kingdom – without reducing the issue to a series of clips narrated by a stand-up comedian – would help people become more tolerant and accepting.

'The world wouldn't change overnight if wildlife programmes showed the homosexuality in the animal kingdom,' he said.

'But anything that helps to normalise all different kinds of sexuality would certainly help to make gay people's lives just that little bit easier.'

The Animals Went in Two by two: Heteronormality in Television Wildlife Documentaries by Dr Brett Mills is published in the European Journal of Cultural Studies, volume 16, issue one, February 2013.