Fiber is one of the most critical elements of a captive gibbon’s diet, as their gastrointestinal tract relies on it to maintain healthy motility, prevent bloat, and support the symbiotic gut bacteria necessary for digestion. In many zoos this fiber requirement is often met using specialised, commercially manufactured primate pellets. Because the availability of these specialised feeds vary from country to country, many sanctuaries need to find different solution to provide a fibre-rich diet.
The good news is, that range country sanctuaries are in a very good position to feed completely natural food items to their gibbons. A continuous supply of locally sourced, non-toxic browse is usually readily available, and provides an excellent fibre and nutrient source. Sanctuary staff should prioritise native species heavily utilized by wild gibbons, such as Ficus (fig) branches, bamboo shoots, hibiscus, and tamarind. Browse should not simply be put into the enclosure once a day. It should ideally be presented several times per day, suspended high in the enclosure, including outside of regular feeding times. This provides a continuous source of slow-release energy and essential behavioral foraging opportunities.
Overall, fiber sources must make up 30-45% of the total diet. Nutritionally, this ensures the diet contains enough fibre, which ferments slowly in the gut to provide sustained energy. By maximising browse and fibrous vegetables, sanctuaries can eliminate the need for sugary commercial fruits, as the complex carbohydrates found naturally in root vegetables, nuts, and leaves provide ample, biologically appropriate energy and nutrients.