Wildlife documentary makers are infringing animals' rights to privacy by filming their most private and intimate moments, according to a new study.

Footage of animals giving birth in their burrows or mating crosses an ethical line that film-makers should respect, according to Brett Mills, a lecturer in film studies at the University of East Anglia.

Mills compiled a report on animals' rights to privacy after reviewing scenes from the BBC's 2009 wildlife series "Nature's Great Events". Among the offending footage was film of a narwhal whale that appeared to have retreated from view beneath the Arctic ice sheet.

"Instead of thinking we'll leave it alone, film-makers decide the only solution is to develop new technology so they can film it," Mills said.

"We have an assumption that humans have some right to privacy, so why do we not assume that for other species, particularly when they are engaging in behaviour that suggests they don't want to be seen?"

In 2008 the BBC was inundated with complaints after Springwatch presenter Bill Oddie described an encounter between two beetles: "He crash-lands on top of a likely looking lady. There's a bit of luck! One thing's for sure: this boy is horny!"

Mills said filming such encounters with miniature cameras was a level of surveillance humans would most likely object to. "The key thing in most wildlife documentaries is filming those very private moments of mating or giving birth. Many of these activities, in the human realm, are considered deeply private, but with other species we don't recognise that," he said. Mills' report appears in the Journal of Media and Cultural Studies.

Mills said that while it might seem odd to claim animals have a right to privacy, the idea should not be dismissed. "We can never really know if animals are giving consent, but they do often engage in forms of behaviour which suggest they'd rather not encounter humans," he said.

The BBC's Natural History unit in Bristol said: "Constantly developing filming technology gives wildlife film-makers the ability to film animal behaviour with minimal disruption to the animal. Film-makers work very closely with scientists whose work studying the complexity of animal lives is vital for wildlife conservation.

"Natural history films play a major role in spreading knowledge of their work. And understanding the world around is vital in the continuing endeavour to preserve our ecosystem."