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San Diego Zoo Welcomes Rare White Rhino Calf After Believing Mother Was Infertile [Video]

By Joanna Jaguar
Published on: 04:53 PST, Apr 8, 2016

A rare white rhino calf has been born in captivity at the San Diego Zoo, a feat once believed impossible with infertility plaguing female white rhinos who had been born in captivity themselves.

The birth of the 5-day-old male calf born to mother Holly at the San Diego Zoo is not only a step in the right direction where Southern white rhino conservation is concerned, but it is also being called a scientific breakthrough by researchers and keepers. According to a press release by the zoo, Christopher Tubbs, a scientist in the Reproductive Physiology Division of the San Diego Zoo Institute for Conservation Research, has been working for eight years to determine why female Southern white rhinos born in captivity face infertility problems far more often than their wild counterparts.

“[S]outhern white rhino females born in zoos—like Holly—tend not to bear offspring as often as their wild relatives. This problem is not found in other species of rhinos living in zoos.”

According to Inside Edition, years of research has led zoologists at the San Diego Zoo to conclude that the diet fed to rhinos in zoos played a major part in their lower fertility. The San Diego Zoo and others used to feed their captive rhinos a diet of pellets containing soy and alfalfa. These ingredients, when ingested, release a compound called phytoestrogens. When female calves are exposed to this compound in the womb through their mother’s diet, it leads to permanent fertility issues later in life.

Keepers at the San Diego Zoo have been actively trying to breed Holly for 10 years, although it wasn’t until they switched her diet to grass-based pellets, rather than those containing the phytoestrogen compounds, that she and two other Southern white rhinos successfully reproduced, says Tubbs.

“Holly showed no evidence of pregnancy for the past 10 years, despite breeding. This successful birth gives us tremendous hope that diet changes can improve fertility in captive-born females of this species, which for decades have struggled to reproduce.”

In order to enact the diet change, the nutritional services team at the San Diego Zoo Global first reduced the number of pellets fed to the rhinos that contained high levels of soy and alfalfa. They then developed the grass-based pellets that are low in phytoestrogens and began giving the rhinos extra nutrients that helped to support reproduction. Approximately two years after the diet change, Holly, as well as two other female Southern white rhinos at the San Diego Zoo — one of whom, like Holly, had never reproduced before — successfully became pregnant.

Finally having given birth to a calf, Holly has adjusted perfectly to the mom life in her enclosure at the San Diego Zoo. Kim Shuler, the senior keeper at San Diego Zoo Safari Park, says that she is very protective of her little boy — who has yet to be named — and watches him closely when others approach him. Holly allows the other rhinos at the zoo to approach the calf, but “gets very vocal” if she feels they’re getting too close for her liking. The calf, who was born April 2 to Holly and father Maoto (pronounced “May-O-toe,” according to the zoo’s press release), has been nursing well and exploring his surroundings at the zoo, which is a great sign, says Shuler.

Fox11 reports that San Diego Zoo Global has been working for more than four decades to keep a “sustainable population of rhinos safe under human care” while also helping to create sanctuaries to protect them in the wild. The Southern white rhino was once thought to be extinct in the late 19th century, but thanks to conservation efforts from the San Diego Zoo and others, it is the only species of rhino that is not on the endangered species list, although increased poaching in recent years threatens to put them back on the list.

[Photo by Lenny Ignelzi, File/AP]

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