San Diego, California - San Diego Zoo staff and volunteers received an unexpected delivery on Monday, November 12th. A 37-year-old siamang named Eloise—who was on birth control—gave birth on exhibit, as volunteers and guests looked on, providing the Zoo with its first siamang infant in more than 12 years.

Siamangs, like many of the animals at the San Diego Zoo and San Diego Zoo Safari Park, take part in the Species Survival Plan (SSP), a breeding program designed to ensure healthy, genetically diverse populations of threatened and endangered species through a network of accredited zoos. As part of the program, Eloise and 35-year-old male Unkie had already been successful parents, producing six offspring over the years. Because their genes are already well represented in the zoo siamang population, the pair’s breeding had been restricted for a number of years by chemical contraception. For that reason, the arrival of their newest youngster this week was a welcome surprise for animal care staff. 

“It was amazing to see Eloise give birth this week, because she showed no outward signs of being pregnant,” said Jill Andrews, animal care manager at the San Diego Zoo. “We’re not certain why birth control didn’t work in this case, but as with humans, it is not uncommon for contraceptive failure to happen from time to time. Still, we are overjoyed—because any birth of an endangered species is a reason to celebrate.”

Siamang are a species of gibbon found in the tropical forests of Malaysia and Indonesia. As with all gibbon species, they are listed as Endangered on the International Union for Conservation of Nature Red List of Threatened Species. Conservationists cite habitat loss, due to logging and agriculture, as the main reason for their population decline. Additionally, many siamang adults are killed so their young can be sold into the illegal pet trade, even though siamangs are a protected species. San Diego Zoo Global supports the conservation initiatives of the Association of Zoos and Aquariums’ Ape Taxon Advisory Group, which works to develop recommendations for population management and conservation, based upon the needs of individual species.

Animal care staff plan to perform a full exam on the infant in the months ahead, and will be able to determine its gender at that time. Currently, Eloise, Unkie, and their newest addition are doing well, and Zoo guests can visit the trio in their habitat along Orangutan Trail, inside the Zoo’s Lost Forest.

Bringing species back from the brink of extinction is the goal of San Diego Zoo Global. As a leader in conservation, the work of San Diego Zoo Global includes on-site wildlife conservation efforts (representing both plants and animals) at the San Diego Zoo, San Diego Zoo Safari Park, and San Diego Zoo Institute for Conservation Research, as well as international field programs on six continents. The work of these entities is made accessible to children through the San Diego Zoo Kids network, reaching out through the internet and in children’s hospitals nationwide. The work of San Diego Zoo Global is made possible by the San Diego Zoo Global Wildlife Conservancy and is supported in part by the Foundation of San Diego Zoo Global.