MIAMI (CBSMiami) – Zoo Miami is trying to uncover a medical mystery involving one of its Sumatran tigers.

Berani, a 12-year-old tiger may be having some fertility issues. As a result, the tiger was immobilized on Monday to undergo an exam evaluating his fertility.

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Though Berani successfully sired an offspring in 2015 and breeding has occurred on several occasions since then, all of the subsequent breeding has resulted in false pregnancies.

The main purpose of this immobilization was to determine if there is an issue with Berani or if there may be a problem with the female, “Leloo.”

(Courtesy: Ron Magill/Zoo Miami)

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The medical experts were able to determine that although Berani is producing viable sperm, the density in the collected samples was very low, highly diluted and not conducive to successful reproduction.

The team is now awaiting the results of blood tests to determine his testosterone level and whether hormone therapy may be an option for treatment.

PIX: Zoo Miami Tiger Undergoes Fertility Exam

While Berani was immobilized, the Animal Health team also performed a series of other procedures including an ultrasound, x-rays, a dental cleaning, blood collection, urine collection and manicure as part of an overall preventative medicine program.

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Sumatran tigers are critically endangered and there are believed to be less than 500 left in the wild where they are found in forested areas on the island of Sumatra in Indonesia.  Their biggest threats are habitat loss to palm oil plantations and poaching.  They are the smallest subspecies of tiger with males reaching up to 300 pounds and females closer to 200 pounds.  Berani represents a very valuable bloodline in the population that is under human care which is why every effort is being made to maintain his ability to contribute to that population.