IT was one of those wildlife-documentary scenes that are very hard to watch. In a drought-stricken part of Africa, a baby elephant is slowly dying of thirst. The mother's instinct is to stay with the weakened calf but at length the calf breathes its last in the dust.

It wasn't surprising that the scene, part of the BBC's Africa series, should upset many viewers, this one included. Sir David Attenborough, speaking about it afterwards, said that while of course he saw "really tough things" in the course of his work, added that there was "nothing you could do about them." Camera crews and wildlife presenters "would actually make things far worse by responding than not." What was important, he said, was to observe.

Other film-makers and camera-operators have made the same point. John Aitchison, asked about filming young black-footed albatross learning to fly in a Pacific location shared by tiger sharks, was once asked why he didn't intervene when one animal attacked another. "I can't intervene – it wouldn't make any difference anyway," he said. "I've mixed feelings because I don't want to see the albatrosses eaten, but that's what I'm here to film."

In Frozen Planet, Doug Allan filmed a pod of killer orcas besieging a Weddell seal on a splinter of ice and eventually dragging it into the sea. Our last glimpse of the exhausted seal before it became the orcas' meal imprinted itself on your brain, much like the scene involving the baby elephant. It was a remarkable, if upsetting, piece of footage, and one that reminded you that this is simply how nature works, whether there's a film crew present or not. Creatures must eat to survive. As Attenborough said, "Many animals suffer as a result of the struggle to find water in the dry season ... you can't intervene. It's the natural order of the world."

Good on Doug, then, for revealing that he sometimes lends a hand provided it doesn't upset the natural balance. He once picked up a little emperor penguin chick that had fallen through a melt-hole in the ice. "Of course," he added, "it will probably just go and fall in another one, but at least you've helped its chances to survive." On the other hand, if he saw some petrels attacking a chick, "you just have to leave it, because the giant petrel is as entitled to his meal as any other animal."

He's right, of course. You can only do so much to help poor little creatures. And I'd guess that even the most ardent animal-lover would have thought twice before taking on these killer orcas to save that poor seal.