Stephanie BrooksA rare tiger, which played an integral role in a breeding programme ensuring the survival of the endangered species, has drowned in her enclosure at Banham Zoo.Stephanie Brooks

A rare tiger, which played an integral role in a breeding programme ensuring the survival of the endangered species, has drowned in her enclosure at Banham Zoo.

Malyshka, a female Amur (Siberian) tiger, was found lifeless in her territory paddock by her keepers early Sunday morning.

Martin Goymour, zoo director, said an extensive post mortem examination has identified the cause of death to be drowning, but how this occurred to an apparently healthy tigress remains a mystery.

More tragically the post mortem also revealed that Malyshka, who was in the top five most important breeding females in Europe, was pregnant with three cubs which would have been of great importance to the international effort to bolster the Amur tigers' falling population. Currently there are believed to be no more than 450 Amur adult tigers left in the wild.

The five-year-old tigress, who could have lived for about 20 years, was mother to two 17-month-old cubs Vasya and Kuzma, whose names were chosen.

'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,' said Mr Goymour.

'All the zoo staff, particularly her keepers, are very much saddened by her loss.

'Further veterinary investigations continue and consultations with the International Studbook Keepers for the Amur tigers will commence immediately.'

Mr Goymour added that Malyshka's mate - 15-year-old male tiger Mischa - had been ruled-out of playing any part in the tragic incident.

Mischa's previous mate Zaliv died of cancer in 2003 and despite efforts to hand rear their two young cubs they also sadly died.

Malyshka was born in Chelyabinsk Zoo in Russia and her arrival in 2006 was heralded as a new beginning for Banham's tiger breeding programme.

Banham Zoo was the only zoo in the UK to receive an official recommendation from the studbook to breed Amur tigers in 2008 and Malyshka gave birth to Vasya and Kuzma in October that year.