A sudden outbreak of avian malaria has killed almost all of a British zoo's penguin colony, leaving staff "heartbroken".
About 50 Humboldt penguins succumbed to the illness at Dudley Zoo in the West Midlands - 70 per cent of the attraction's total number.
The disease is caused by infected mosquitoes and changes in the weather.
Zoo director Derek Grove said staff had "never experienced anything like it before".
"Unfortunately, penguins are particularly susceptible to the disease as they do not have natural resistance against it and it’s also not easily identifiable through medical tests," he said.
"We do not know if last year’s unusual weather pattern has played a part, with wet and muggy weather not only impacting the penguin’s moulting season, but also increasing the risk of mosquitoes.
"But what we do know is we now need to focus on continuing to treat the remaining birds and putting in place additional preventative measures to avoid this tragedy happening again."
The zoo said it had enjoyed "great success" breeding Humboldt penguins over the last 30 years.
It started out with just five hand-reared chicks in 1991 and went on to have one of the largest self-sustained colonies in the UK.
The zoo had 69 Humboldts when the avian malaria outbreak happened.
Derek said the population was also used to help boost new groups at collections around the country.
He said: “We are all heartbroken with the huge loss in Penguin Bay and it’s been an especially distressing time for our bird team who have devoted years to their care.
“Their dedication and tireless efforts to care for our penguins over recent weeks has been exemplary.
"They’ve provided round-the-clock care to individually treat the birds in their fight to save as many as possible and we thank them for their determination.
“Having consulted with avian experts and animal collections around the world, we know we’ve done all we can.”
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