Kiazi and her new-born calf at the San Diego Zoo Safari Park. Courtesy of the zoo

Researchers at the San Diego Zoo are using dietary changes to help endangered white rhinoceroses give birth in captivity.

A rhino calf was born at the Safari Park on April 30 to a 16-year-old mother, Kiazi, whose age was well past the the average for first-time births.

Christopher Tubbs, a senior scientist at the zoo’s Institute for Conservation Research, and his colleagues determined that compounds found in the soy and alfalfa pellets fed to rhinos were limiting their fertility.

Thse plants contain “phytoestrogens,” which mimic the action of hormones.

“The birth of Kiazi’s calf gives us a great deal of hope that by feeding low phytoestrogens at our institution and others, we can once again have a healthy, self-sustaining captive southern white rhinoceros population,” said Tubbs, who added that wild rhinos are increasingly the victims of poachers.

Since the zoo began experimenting with the new diet in 2014, there have been three pregnancies in females that had not successfully reproduced before.

The researches said it is likely that a number of species living in zoo settings receive diets containing levels of phytoestrogens capable of affecting reproduction.

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Chris Jennewein

Chris Jennewein is Editor & Publisher of Times of San Diego.