Two giraffes at a zoo in central Poland's Lodz died of stress after unidentified vandals went on a night-time rampage, the zoo's management said Monday.
The vandals broke in overnight Saturday to Sunday, destroying benches, signs and sculptures and hurling pieces of the debris at the animals.
One of the giraffes died within hours of the incident and the second was found dead Monday morning.
"The autopsy of the first giraffe, three-year-old female, found a ruptured heart valve and bruising, a sign of a severe stress reaction," the zoo's deputy director Wlodzimierz Stanislawski told AFP.
"The second, a six-year-old female, was slightly ill before the incident. The stress likely aggravated the illness and finished her off.
"Giraffes are extremely timid. Stress causes a flight response in them. They react the same way to every unusual noise," said Stanislawski.
The zoo is not equipped with surveillance cameras and night security guards did not notice anything unusual.