The new addition is expected in the spring of 2020.

Talk about keeping a secret! The Denver Zoo announced on Sunday that its 11-year-old rhino, Tensing, is expecting her first calf. But because rhinos have a 15- to 16-month gestation period, zoo officials have known about the little bundle of joy since conception in November 2018!

The zoo kept it quiet because they didn't want to announce the pregnancy before it was far enough along to be viable and long-term. There is a good reason behind this, as this particular announcement is a rarity that came about after years and years of trying. 

“Tensing’s pregnancy is an incredible example of what Denver Zoo—and other zoos accredited by the Association of Zoos and Aquariums—do to ensure the survival of many vulnerable, threatened and endangered species,” said Brian Aucone, Senior Vice President for Animal Sciences. “This was a multi-year process that involved countless hours of care and training, and the cooperation of partner zoos.”

Tensing came to the zoo in 2011, where she worked with handlers to participate in the breeding process, which was via artificial insemination. After several unsuccessful tries, she was treated for excess fluid in her uterus, and it seemed to do the trick because she is now pregnant. 

"On November 11, 2018, Drs. Moresco and Stoops attempted a 12th artificial insemination procedure with sperm from Jontu, a 10-year-old male greater one-horned rhino from Omaha’s Henry Doorly Zoo and Aquarium," the zoo said in a release. "A voluntary ultrasound 10 days later suggested she was pregnant. Her pregnancy was confirmed 23 days after insemination by observing the embryo on ultrasound, and subsequent weekly voluntary ultrasounds have shown her fetus is healthy and has grown to roughly the size of a large watermelon. He or she is due in late March or early April 2020."

Tensing and her current habitat mates are greater one-horned rhinos. Due to hunting, it is estimated that only 200 of the species remained in the wild when it was on the brink of extinction in the early 20th century. Today, the population has grown to 3,500 and managed breeding programs are helping to ensure species survival.

You can visit Tensing and the other zoo rhinos in the pachyderm habitat at the zoo.