San Diego Zoo Global’s First Southern White Rhino Calf Conceived Through Artificial Insemination Turns 1 Year Old
Birthday Celebration Held in Edward’s Honor
Southern white rhino Edward turned 1 year old on July 28, 2020, and a birthday celebration was held in his honor at the San Diego Zoo Safari Park’s Nikita Kahn Rhino Rescue Center. With San Diego Zoo Global researchers and wildlife care specialists looking on, the little rhino charged into the Rhino Rescue Center outdoor area with his birthday “guests”—his mother Victoria, 8-month-old female calf Future, and her mother Amani—following close behind. The area was decorated by wildlife care specialists and Safari Park volunteers, with cardboard cutouts of rhinos, decorative boxes filled with the rhinos’ favorite hay, a big birthday banner and a specially made mud wallow.
Edward’s birth marked a significant event for San Diego Zoo Global: He was the conservation organization’s first rhino born following hormone-induced ovulation and artificial insemination. Artificial insemination of southern white rhinos has rarely been successful in the past; there have been only two successful artificial insemination births of a southern white rhino in North America—Edward and female calf Future, also born at the Safari Park, to mom Amani, on Nov. 21, 2019.
“Even though he doesn’t know it’s his birthday, it is very special to see Edward – a healthy, robust rhino - running around, enjoying his special treats,” said Barbara Durrant, Ph.D., Henshaw endowed director of Reproductive Sciences, San Diego Zoo Global. “We aren’t just celebrating his birthday but also are celebrating the significance of his birth. Edward and Future’s births validate our techniques of semen freezing, ovulation induction and artificial insemination. In addition, their mothers are now “proven females” who have demonstrated their ability to carry a calf to term and raise it successfully. These births are symbols of the great progress made toward the eventual goal of transfer of northern white rhino embryos and hope for the future of the critically endangered northern white rhino.
Edward’s mother, Victoria, was artificially inseminated with frozen semen from southern white rhino Maoto on March 22, 2018, following hormone-induced ovulation. She gave birth to Edward 16 months later. The artificial insemination and successful birth of Edward represented a critical step in the organization’s ongoing work to develop the scientific knowledge required to genetically recover the northern white rhino, a distant subspecies of the southern white rhino. Only two northern white rhinos currently remain on Earth and, unfortunately, both are female.
To reach the ultimate goal of successfully producing a northern white rhino, multiple steps must be accomplished. One of the first steps completed involved sequencing the genome of the northern white rhino to clarify the extent of genetic divergence from its closest relative, the southern white rhino. The analysis revealed that they are distinct subspecies. Another step requires conversion of cells preserved from 12 individual northern white rhinos in the Frozen Zoo® to stem cells that could develop into sperm and eggs—a process currently being worked on in the conservation genetics lab at the San Diego Zoo Institute for Conservation Research.
Reproductive options include artificial insemination, in vitro fertilization and embryo transfer, working with southern white rhinos. When these techniques are perfected, the southern white rhinos would serve as surrogates for northern white rhino embryos. With the success of the recent artificial insemination resulting in two healthy calves, Durrant and her research team are now focused on perfecting in vitro embryo production and embryo transfer.
San Diego Zoo Global is working as part of the International Rhino Reproduction Collaborative (IRRC), consisting of six groups in South Africa—University of Pretoria, Embryo Plus, Buffalo Dream Ranch, Institute of Rhino Cryogenics, South African National Parks and GEOlifes.
Researchers from San Diego Zoo Global and Embryo Plus South Africa performed successful ovum pick-up (OPU) procedures on four female southern white rhinos at the Nikita Kahn Rhino Rescue Center on March 6, 2019, and on rhinos in South Africa in February of this year. OPU is a non-surgical method of collecting eggs from a live animal. Modeled after a common method used with cows and horses, OPU has been perfected on southern white rhinos by San Diego Zoo Global collaborator Dr. Morné de la Rey, director of Embryo Plus South Africa.
After retrieval, the eggs are matured in vitro, fertilized by intracytoplasmic sperm injection (ICSI), then cultured through development to the blastocyst stage—the last stage prior to implantation of the embryo in the uterus. Traditional in vitro fertilization involves using thousands of sperm for each egg, while ICSI uses a single sperm to fertilize a single egg. Embryo transfer has yet to be successful in rhinos. Once this is perfected, embryos developed from these in vitro procedures could be transferred into one of the southern white rhinos at the Nikita Kahn Rhino Rescue Center to produce a southern white rhino calf.
The reproductive system of rhinos is very complex, and there is still much to be learned. There are many challenges ahead, but researchers are optimistic that a northern white rhino calf could be born from these processes within 10 to 20 years.