Does anything live at the top of Mount Everest?

TERRESTRIAL HABITATS DON'T GET ANY higher than the summits of Himalayan peaks. And Himalayan peaks don't get any taller than Everest.

- Stuart Blackman

At 8,849m above sea level, the summit is exposed to extremes of wind, cold and oxygen-deprivation. Life is sparse at such heights.

Humans are almost certainly the only mammals to have set foot up there and, even then, only with technological assistance, and we don't tend to hang around for long. The only other mammal that gets close is the large-eared pika, a relative of rabbits, which reaches 6,400m in the Himalayas (though yellow-rumped leaf-eared mice have been recorded on the 6,739m-high summit of Llullaillaco in the South American Andes).

It might be that no life-forms bigger than a single cell can eke out a living on the roof of the world. Mosses aren't found higher than about 6,500m, for example. Among invertebrates, a single species of jumping spider ventures up to 6,000m, where it probably feeds on hapless insects blown in from elsewhere. Birds are mobile enough to drop by occasionally, though. Yellow-billed choughs have been spotted at 7,900m, and mountaineers have reported bar-headed geese flying over the summits of Everest and nearby Makalu.

Why does New Zealand have so few mammals?

EVOLUTION HAS GREAT FUN ON ISLANDS. Their isolation means it has the luxury of working its magic for long periods away from mainland gene pools. The Galápagos, Hawaii, Madagascar, Mauritius all teem with species that are found nowhere else. And sitting all on its own in the south-west Pacific, 2,000km from the nearest landmass, New Zealand is no exception. More than half of its native species are endemic, including ancient and unique lineages of reptiles and plants and a spectacular variety of strange flightless birds. And yet something is missing.