Investors too might temper their enthusiasm for tracking stocks, by giving some thought to how they might perform in a sharply falling market.

ECONOMIST: Shares: Making tracks | The

The bird had surgery to remove sand from its stomach - which it is thought to have eaten thinking it was snow - before being released with a tracking device.

BBC: Lost Antarctic penguin dies in New Zealand zoo

He had surgery to remove 3kg (6.6lb) of sand from his stomach, which he is thought to have eaten thinking it was snow, before being released with a tracking device.

BBC: Lost Antarctic Royal penguin found in New Zealand

Tracking food-borne disease is also complicated by the number of illnesses thought to be caused by unknown pathogens.

ECONOMIST: Food poisoning