Steele, T. L., Butler, N. A., Segar, M. T. et al. 1995. Preferences for food location and foraging requirements in white-handed gibbons. American Zoo and Aquarium Association (AZA) Regional Conference Proceedings, 151-158.

Mixing ice with the food [in buckets] reduced eating time slightly but substantially increased foraging time. Foraging was much more extensive from the top bucket and significantly more food was gathered from this source than from the bottom bucket. The dominance of the male during feeding suggests that more than one food source should be available for multiple animals.