LONDON, England (CNN) -- A rare Komodo dragon has died after falling from a wall while trying to reach her mate at London Zoo.
The zoo had hoped that 10-year-old Nina and Raja, six, would eventually mate, and help save the species.
Scaling the wall in her new state-of the art enclosure was "both spontaneous and entirely out of character" behavior, the zoo said in a statement.
Nina, who was 6.5ft long and weighed 44lbs, died of internal bleeding on Wednesday, the zoo said.
She was injured after climbing a dividing wall, which ranges from 7.2ft to 8.2ft high, and falling into Raja's section.
London Zoo insisted the Komodo house, which took seven months to build, had been completed to the highest possible specifications.
"The design of the enclosure was thoroughly researched drawing on the knowledge of the world's leading reptile experts, but sadly this individual female dragon's agility far exceed our expectations and research," curator Dr David Field said.
"Immediate measures are being put in place to prevent a similar incident happening again and we are carrying out a thorough investigation into what occurred."
However, a spokesman for the Royal Society for the Prevention of Cruelty to Animals said the organization was "shocked" by the death.
"The full biological needs and abilities of any animals should be fully assessed before they are placed in a captive environment.
"From the information we have been provided with, it appears this was not done in the case of the Komodo dragons.
"We are frankly shocked that London Zoo was so ill-prepared -- especially given the rarity of the species.
"Komodo dragons are large, strong animals that can be aggressive towards each other.
"From what we have been given by, it appears these well-known biological facts were not taken into account in the design of the captive-facilities at London Zoo."
But Miranda Stevenson of the Zoo Federation, the professional association for zoos in Britain and Ireland, said: "Like everyone else we thought it was an ideal state-of-the-art enclosure.
"It is really unfortunate that the animal appears to have performed some acrobatics that no one could have anticipated."
The large lizards eat deer and water buffalo in the wild and have been known to devour humans.
They inhabit a small number of Indonesian islands and can live for 20 years. There are believed to be about 5,000 left in the wild.