ROYAL OAK, Mich. (CBS DETROIT/ AP) — An 11-year-old gray wolf named Wazi died during surgery to remove a mass in her chest, the Detroit Zoo says.

She suffered cardiac arrest and died Monday.

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The mass was discovered during a health exam and veterinarians determined surgery was the only option because of its size and location.

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The Detroit Zoo said in a statement Wazi “was intelligent, fearless, curious and sassy,” and “adored” by employees, volunteers and visitors.

The zoo’s lone surviving wolf is a male named Kaska.

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