A pregnant tiger which was part of an international breeding programme has drowned at a British zoo.
Malyshka, a five-year-old Siberian Amur tiger, was carrying three cubs when she died at Banham Zoo, near Norwich, Norfolk.
The species is on the brink of extinction with just 450 adults left in the wild and Malyshka was ranked in the top five most important breeding females in Europe.
Her keepers are baffled by her death because she was in good health and drowned in just a few feet of water.
Zoo director Martin Goymour said: ”Malyshka was such a strong and healthy tigress and showed no signs of external and internal injuries. The pool in the enclosure is not deep or considered hazardous.
”All the zoo staff, particularly her keepers, are very much saddened by her loss.”
Malyshka was central to a worldwide breeding programme aimed at boosting numbers of the endangered species.
Her keepers did not know she was pregnant until the post mortem was carried out following her death.
Experts at the International Studbook Keepers for the Amur tigers are now investigating.
Malyshka was born in Chelyabinsk Zoo in Russia and arrived as part of a breeding programme in 2006.
She could have lived for about 20 years and was mother to two 17-month-old cubs Vasya and Kuzma.
Her mate – 15-year-old male tiger Mischa – has been ruled-out of playing any part in the death.
Mischa’s previous mate Zaliv died of cancer in 2003 and despite efforts to hand rear their two young cubs they also sadly died.