Zoo general manager Jody Henderson says officials made the decision early Tuesday afternoon because the large cat had lost its appetite, was in respiratory distress and was lethargic.
Henderson says officials were expected to conduct a necropsy later in the day.
Henderson says Sweetie was under constant veterinary care for the past month, and while officials tried medication and stimulating its appetite, the animal's condition continued to decline.
Sweetie was born at the zoo that's located about 45 kilometres east of Vancouver.
Henderson says the median life expectancy of female Siberian tigers is 14 years in captivity, and there are only about 400 to 500 living primarily in eastern Russia, although some exist in China and North Korea.
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