An endangered Sumatran tiger has been killed by another tiger at London Zoo. Male tiger Asim was brought to the zoo from a Danish safari park 10 days ago in the hope he would be the "perfect mate" for long-term resident Melati.
After spending time apart in the tiger enclosure to get used to the new arrangement, the two were then introduced to each other earlier.
But tensions "quickly escalated", things became "more aggressive" and Melati died in a fight, the zoo said.
A statement issued by the zoo said Asim was immediately moved to a separate paddock but despite the best efforts of the vets, 10-year-old Melati died.
It said: "Our focus right now is on caring for Asim, as we get through this difficult event."
Staff are "heartbroken by this turn of events", the zoo said.
Seven-year-old Asim was moved to London Zoo as part of the European-wide conservation breeding programme.
Heralding his arrival, the zoo described him as "a handsome, confident cat who is known for being very affectionate with the ladies in his life", adding that "we're hoping he'll be the perfect mate for our beautiful Melati".
The zoo's previous male, Jae Jae - which had fathered seven cubs previously with Melati - was moved to French zoo Le Parc des Félins, on 30 January.
In 2013, Melati gave birth to two cubs but one fell into a pool and drowned.
Melati then gave birth to three cubs in February 2014 and two more in June 2016.
The Sumatran tiger, which naturally lives in the forests and jungles of Sumatra, Indonesia, is now classified as critically endangered and is on the International Union for Conservation of Nature's red list of threatened animals.
According to London Zoo, the Sumatran tiger faces threats of poaching and habitat loss.
When in captivity, they can live for about 20 years.
In the 1970s, there were estimated to be 1,000 Sumatran tigers in the wild, while today's figures say there are just 300.