The San Diego Zoo said within two years of changing the rhinos' diet, three rhinos became pregnant.
After many years of infertility, a San Diego Zoo white rhino gave birth to her first calf.
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The male calf, who has not yet been named, was born last week, and can be seen learning to walk as his mother, Holly, keeps a protective eye over him nearby.
"Holly is an excellent mom and very protective of her newborn," said Kim Shuler, a keeper at the San Diego Zoo. "She allows the other rhinos to approach, but gets very vocal when they venture too close to her little guy.”
While the new southern white rhino is a significant addition to its dwindling population, officials say the birthing of the animal in captivity is a scientific breakthrough.
According to a press release, "southern white rhino females born in zoos --- like Holly --- tend not to bear offspring as often as their wild relatives." Even though Holly has been actively breeding for the last ten years, this is the first calf she was able to conceive.
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The press release stated the original belief was that rhinos born in captivity were exposed to compounds while in their mother's womb, "resulting in permanent infertility issues later in their life."
Zoologists now think the lower fertility rates of rhinos born in captivity is due to their diet. Zoos often feed the rhinos pellets that contained a high amount of soy and alfalfa, which released a compound called phytoestrogens.
After they changed the rhino's diet to a grass-based pellet, the San Diego Zoo said three rhinos became pregnant within two years. Two of the rhinos had never previously conceived.
“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," said Dr. Christopher Tubbs, a reproductive scientist at the San Diego Zoo Institute for Conservation Research, according to a press statement.
Zoo officials say the breakthrough comes at a good time, when poaching levels have become higher than ever. In 2015 alone, the San Diego Zoo reports that over 1,400 rhinos were poached in the wild, a shocking 100 times more than just eight years previous.
"Holly has not had a calf before, so genetically this calf is very valuable to the population," Tubbs said.
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According to the WWF, the southern white rhino was thought to be extinct in the late 19th century, but a small population was discovered in South Africa.
The southern white rhino is now the only species of rhinos that are not endangered, yet they face the risk of endangerment due to the high number of poaching in recent years.
Southern white rhinos are often poached for their horns, considered to be medicine or symbols of wealth in some cultures.
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