In 2024, EAST released five southern golden-cheeked gibbons (Nomascus gabriellae) back into newly protected forest in South Vietnam. The adults Kizzy and Dong were both fitted with Lotek Lite Track GPS/ satellite collars and are being successfully monitored post-release.
In September the family of five (Kizzy, Dong with offspring Bich, Tuyen and Fizzy) were transferred to a release site, in newly protected continuous forest within the natural geographical range of the species. The newly protected area holds no wild gibbons, but is continuous with older established populations of gibbons further north. Kizzy’s family, after growing up in a forested enclosure on Dao Tien were captured for transfer to the in-situ release cage, with both adults successfully fitted with Lotek Lite GPS/ satellite collars. This type of collar only in the last years has become small and light enough to be worn by 7 kg primates. The collar is able to link up with satellites to transfer the daily GPS locations of the gibbons, so if the gibbons suddenly travel beyond the range of the VHF beacon, we can still locate them.
Thanks to support from ARCUS foundation, a dedicated post-release monitoring team, who track the gibbons daily, providing supportive feeding and ensuring all family members are healthy is possible in the first phase. In combination with the ground team and the GPS locations we are understanding more about the complex life of gibbons, especially decision making immediately after release. Gibbons are known to have a flexible social system, monogamous, polygamous family groups, with extra pair paternity and even divorce common. Thus they are familiar with considering other options!!
The driving force behind Nomascus families is resource availability, the patch of fruit trees they actively defend. The defence of this area (territory) appears to influence many of the gibbon’s behaviours, such as their song. The Nomascus duet, between the male and female can be quickly learnt, not taking years to perfect as documented with other gibbon genus. The song is very much driven by the female. The female adjusts her contribution drastically based on food resources and potential competition from neighbouring females. This can be the difference of a duet with a female contribution of one great call (the female part of the song), or thirty great calls. This variation correlates with resource threats or simply abundance. Thus the availability of resources play a large role with partner choice, potential more than simply than the love of your partner in Nomascus!
If the resource (territory) is key to gibbon social behaviour, then any new releases are very challenging, as the family have no territory at first. The female needs to make the decision to stay with her male who does not (yet) have a territory, instead of seeking out other males somewhere who are more secure. Monitoring gibbons closely over this initial phase is key… thanks to our ground team and satellite collars we can do this with Kizzy’s family. For more updates please SPONSOR
We are already preparing Hoi & Vang for release in 2025, and need donations to support post-release tracking.
We appreciate any help you can give!