Originally published December 23, 2013 at 8:28 a.m., updated December 23, 2013 at 12:18 p.m.
The San Diego Zoo was investigating Monday why a 4-year-old female Malayan tiger was killed by a male tiger when the two were introduced for breeding purposes.
The death took place Saturday before the park opened and was not witnessed by visitors, according to the zoo.
Jennifer Mehlow, a park spokeswoman, said the introduction was routine and started off well.
"Unfortunately this changed quickly and zookeepers were unable to separate the two animals," Mehlow said.
This is the first time one tiger has killed another during a mating session at the zoo, Mehlow told City News Service.
However, large carnivores often mix aggressive behavior with breeding interactions and this sometimes results in injury or death, according to zoo officials.
The female tiger, Tiga Tahun, was brought to San Diego earlier this year for breeding purposes in an effort to propagate the endangered species, according to the zoo. She was born at the Bronx Zoo but was part of a collection owned by the Omaha Zoo, Mehlow said.
Connor, the male, was born in 2011.