Four tiny "vampire" deer are being hand-reared by zookeepers to protect them from predators.
The Chinese water deer measured just 12cm (5ins) at birth two weeks ago and weighed the same as a can of soft drink.
Zookeepers at Whipsnade Zoo in Bedfordshire have been looking after them to stop them being picked off by birds of prey.
Keeper Gracie Gee said: "Even at their present weight of 800g large birds could still easily scoop them up, so we are hand-rearing the fawns in a sheltered, protected space at the zoo."
Ms Gee said the small spotted fawns - which have giant ears to help them better hear approaching threats in the wild - will soon move to their new home at London Zoo.
She said: “We’ve been giving the little ones, who are all female, at least three feeds a day and they’ve already doubled in size since their births in early June.”
Chinese water deer are sometimes known as vampire deer because they have a set of sharp fangs.
They are listed as vulnerable on the International Union for Conservation of Nature Red List of threatened species, as populations in the wild continue to decline in the face of threats including habitat loss and hunting.
Some of their original populations are now extinct in mainland China, making their conservation in the UK more important.
The Zoological Society of London, which runs Whipsnade and London Zoo, said its Chinese water deer could be used to help repopulate the species in China.
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