Rare White Rhino Thought to Be Infertile Welcomes Baby Boy at San Diego Zoo

The birth of a male southern white rhino at the San Diego Zoo Safari Park is being heralded as a breakthrough in zoo breeding programs

The birth of a male southern white rhino at the San Diego Zoo Safari Park is being heralded as a breakthrough in zoo breeding programs.

According to the zoo, unlike other species of rhino, southern white rhinoceroses born into zoos often have trouble breeding. Christopher Tubbs, Ph.D., a scientist in the Reproductive Physiology Division of the San Diego Zoo Institute for Conservation Research, and his team were tasked with studying what could cause this fertility issue. After extensive research, the group determined the rhino species might be sensitive to certain compounds in soy and alfalfa found in the diet of these zoo animals. The scientists found that long-term exposure to these components, called phytoestrogens, may have lead to the animals’ infertility.

To see if the hypothesis was correct, the zoo changed the diet of all its southern white rhinos. Instead of soy and alfalfa pellets, the rhinos were fed grass-based pellets. Two years after the diet change, Holly and two other rhinos that the zoo believed were infertile became pregnant. It was Holly who welcomed the safari park’s newest arrival on April 2, along with her mate Mateo.

“Holly showed no evidence of pregnancy for the past 10 years, despite breeding,” said Tubbs. “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.”

Even more good news, the new calf is doing well, already curiously walking around his habitat.

“We are very excited Holly gave birth to a healthy calf,” stated Kim Shuler, senior keeper, San Diego Zoo Safari Park. “The calf is nursing well, which is a great sign. Holly is an excellent mom and very protective of her newborn. She allows the other rhinos to approach, but gets very vocal when they venture too close to her little guy.”

The arrival of this calf, who is still unnamed, and the other expected babies is important to the rhino population, which is suffering in the wild. Due to the increase in poaching, the number of southern white rhinos in the wild has dwindled to 18, 000. If poaching continues at its current rate, the rhino species could be extinct in 15 years.