A leopard died when she fell 13 feet (four metres) after being tranquilised during an attempt to stop her escaping from her cage.
Jade came to live at Marwell last year and was about to move cages
Jade, a two-year-old Amur leopard, failed to wake up after being shot with a tranquiliser dart as she squeezed through a roofing net.
She was being introduced to the new leopard enclosure at Marwell Zoological Park in Winchester, Hampshire, on Monday when the incident happened.
Jade climbed a tree inside the cage and managed to push through an opening in the roof.
A spokesman for the zoo said the general curator then fired a dart to knock Jade out so she could be returned to her home cage, but she fell on to the roof of her enclosure and never recovered.
Chief executive of the zoo, Mark Edgerley, said: "She fell about four metres but unfortunately she got lodged in a fork of the tree.
"We recovered her and tried to revive her, but she died.
"We expected her to recover from the fall as she would have been limp.
"We do not know what caused the death and a post-mortem examination is taking
The zoo has called off Saturday's grand opening of the new big cats cage and managers have begun an investigation into the death.
The incident happened before doors had opened for the day.
Jade arrived at Marwell last year, after being born at Cricket St. Thomas in Somerset.
The cat, which is the size of a labrador, is extremely rare with only 33 believed to be in the wild and just over a 100 in captivity across the world.