By Emily Sexson

Zoli, one of the siamangs residing here at the Lee Richardson Zoo, has many fans, but not many people know his incredible story. Fourteen years ago, in the early morning of February 20th, 2007, a new life entered the world at the Louisville Zoo in Kentucky. The Association of Zoos & Aquariums' Species Survival Plan for Gibbons successfully matched siamang pair Sue Ann and Ziggy, and Sue Ann was now rearing her son, Zoli. Everything was going well for the siamang family until tragedy struck a few months later when Zoli’s parents had both died suddenly, leaving Zoli orphaned. At just two months old, Zoli would still have been clinging to and nursing from his mother. Zoo staff acted quickly and began hand rearing Zoli.

Siamang are an endangered species. They are arboreal, black-furred gibbons native to the forests of Indonesia, Malaysia, and Thailand. Gibbons are also known as lesser apes or small apes. Siamang are the largest of all gibbon species, weighing around 23 pounds; they can be twice the size of other gibbons. Gestation for siamang is approximately seven and a half months, with a single offspring born every two or three years.

Siamang babies will nurse from their mothers for around two years. Keepers at the Louisville Zoo stepped into this role, providing bottle feedings multiple times a day, every day for two years. Staff would wear black fleece so that Zoli could climb and cling to them, just as he would his mother. While they were hand rearing Zoli, staff monitored his health and watched as he reached other milestones, which are very similar to those of a human infant; his first call, his first time sitting up, his first time crawling, his first solid foods, and so on. Zoli was thriving! 

That summer, Zoli was introduced to 9-week-old siamang siblings Zain and Sungai. The brother and sister pair had been rejected by their mother at birth. While Zain was hand-reared from birth, his sister Sungai was paired with a surrogate at another facility. Unfortunately, the surrogate did not accept Sungai, and she rejoined her brother, and the pair joined Zoli. Staff encouraged appropriate behavior in the three “kids”, and they soon began spending all their time together. 

Siamang family groups usually consist of a bonded male and female pair with two to three immature offspring. Offspring mature at about six years old and will leave their family in search of a mate, reaching sexual maturity around eight or nine years old. After developing and growing with Zain and Sungai in Kentucky, just as he would have in the wild, Zoli was ready to leave his family group to find his mate. In 2017, Zoli came to the Lee Richardson Zoo under recommendation from the Siamang Species Survival Plan. In 2020 the Species Survival Plan matched Zoli with Violet, who came to the zoo from Disney’s Animal Kingdom.

With their very distinctive call, which they use for territorial and bonding purposes, you may hear Zoli and Violet at the zoo before you see them. Siamang move by brachiating (swinging arm over arm), under branches, flying through the air, easily moving from one platform to the next. Watching Zoli and Violet move about their habitat is always a sight to see! Since their introduction, Zoli and Violet have been getting to know one another and are developing their relationship. We look forward to watching the pair’s relationship continue to progress. 

The biggest threat to all wildlife is habitat loss. We can help siamang and other species by committing to sustainable choices. You can help siamangs here at home by recycling products like glass, aluminum, and paper, which are made from resources found in their native rainforest habitat. Many of the paper products we buy in the United States come from trees sourced from Indonesia. By reducing our use of these products, and finding ore sustainable options, we can protect their natural home. 

Zoli and his siblings are just one example of the struggles and amazing successes that animals and staff at facilitates accredited by the Association of Zoos and Aquariums experience as we work towards our goal of conserving wildlife across the world. This Saturday, February 20th, help us celebrate Zoli’s 14th birthday by visiting him at the zoo, recycling, and purchasing rainforest-friendly products. Happy Birthday, Zoli!

Emily Sexson is a communication specialist at Lee Richardson Zoo.