Sir David Attenborough's wildlife documentaries do not show enough gay animals, a study has shown.
Research carried out at the University of East Anglia in England found BBC wildlife documentaries hosted by the famous nature documentary-maker portray animals as heterosexual families too often, even though animals can also be gay.
Dr Brett Mills who carried out the study said: 'The central role in documentary stories of pairing, mating and raising offspring commonly rests on assumptions of heterosexuality within the animal kingdom.'
This is despite much evidence which shows many animals have 'complex and changeable forms of sexual activity, with heterosexuality only one of many possible options,' according to Mills.
The study was based on the three UK BBC wildlife documentaries The Life of Birds, The Life of Mammals and Life in the Freezer, and Dr Mills says the way animals are described by the presenter make a big impact on how they are portrayed as straight.
But all the shows researched date from 1993 to 2002 and newer programs haven't been included in the analysis.
'Voiceovers tell the audience how to make sense of what is being seen. The environment, via the voiceover, is interpreted and understood via decidedly human cultural norms and assumptions', he said.
Dr Mills also said the shows rely on the idea that 'surival of the species depends on "traditional" family units with the requisite number of parents and offspring with biological ties.
'The descriptions of animal behaviour, because of their association with the "natural", play a telling role in the policing of human behaviour', he added.
The study was published today in the European Journal of Cultural Studies. The BBC today could not be reached for comment.