The use of tools for throwing is rare among animals and has only been documented in a few cases in captive apes, including chimpanzees (Pan troglodytes), bonobos (Pan paniscus) and gorillas (Gorilla gorilla gorila), but also in captive and wild capuchin monkeys (Sapajus spp.). Gibbons (family Hylobatidae) or lesser apes are a uniform group of territorial and mostly pairliving apes that are well known for emitting loud calls and using a fast form of locomotion
known as brachiation, which is an adaptation to arboreal life in the treetops. These adaptations also include the morphofunctional properties of the hand, such as long fingers, a narrow palm and greater mobility of the thumb. To date, only one unsystematic study by Denga and Zhou (2016, Sci. Rep. 6, 23566) has documented that only wild male Hainan gibbons (Nomascus hainanus) perform the spontaneous and repeated throwing and catching of sticks in their hands, suggesting higher level of throwing. The aim of presented pilot study is to analyze this unique behavior in captive northern white-cheeked gibbons (Nomascus leucogenys) and southern yellow-cheeked gibbons (Nomascus gabriellae). Records of juggling-like behavior were collected in Czech zoological parks. We analyzed 103 records obtained from 8 individuals ranging from 2 and 30 years of age. The data were analyzed using a Mann-Whitney U test in R software, version 4.3.3. For each juggling-like behavior, we determined the total time duration (seconds) with the number of throws, the sex of the juggler, the context (food or nonfood) and which hands were used. We found that males had a longer duration of juggling-like behavior (P=0,017) and a higher number of throws (P=0,012) than females. Regardless of sex, we found that gibbons had longer durations of juggling-like behaviour (P