Captive gibbons in Thailand and the option of reintroduction to the wild

Published source details Eudey A.A. (1991) Captive gibbons in Thailand and the option of reintroduction to the wild. Primate Conservation, 12, 34-40.
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This study is summarised as evidence for the following.

	Action	Category
	Reintroduce primates into habitat where the species is absent Action Link
	Implement legal protection for primate species under threat Action Link
	Regularly and continuously provide supplementary food to primates Action Link
	Reintroduce primates into habitat where the species is present Action Link
	Permanent presence of staff/manager Action Link
	Allow primates to adapt to local habitat conditions for some time before introduction to the wild Action Link
	Reintroduce primates as single/multiple individuals Action Link
	Treat sick/injured animals Action Link
	Reintroduce primates in groups Action Link

Reintroduce primates into habitat where the species is absent

A study, which was included in a review, in 1967–1970 on the island of Koh Klet Kaeo, Thailand found that reintroduction, along with other interventions, led to declines of 60% in the population of formerly captive lar gibbons Hylobates lar over three years. No statistical tests were carried out to determine whether this decrease was significant. Four infants were born to the introduced population of 20 gibbons (reproductive rate =20%). Twenty gibbons were introduced in pairs into habitat that did not resemble their natural habitat and without resident gibbons. Gibbons were obtained from commercial animal dealers and housed in a laboratory for at least one month along with the gibbon with whom they were released on the island. Gibbons were fed and provided with water from artificial food and water stations. In 1961, gibbons were officially protected by the Thai government. The study does not distinguish between the effects of the different interventions mentioned above.
Implement legal protection for primate species under threat

A study, which was included in a review, in 1967-1970 in Koh Klet Kaeo island and Sai Yok National Park, Thailand of lar gibbons Hylobates lar that were legally protected in 1961 along with other interventions and that were reintroduced from captivity found that the introduced population of 20 individuals decreased to eight individuals (60% decrease) over three years. No statistical tests were carried out to determine whether this difference was significant. However, four infants were born over the same time period. Gibbons were introduced in pairs into habitat that did not resemble their natural habitat and without resident gibbons. Gibbons were obtained individually from animal dealers and housed together in a laboratory for at least one month before release. They were supplemented with food and water. In dry evergreen forest in Sai Yok National Park, two introduced gibbons of a total of 31 individuals died (6% decrease) within three years post-release and no infants were born in the first 17 months. Four gibbons joined wild groups. They were introduced as individuals, pairs, or family groups into habitat with resident conspecifics. Anaesthetized gibbons were either kept in separate cages for 14 days before release, or laid out on the forest floor. Injured animals were recaptured and treated. The study does not distinguish between the effects of the different interventions.
Regularly and continuously provide supplementary food to primates

A study, which was included in a review, in 1967-1970 on Koh Klet Kaeo island, Thailand of captive lar gibbons Hylobates lar that were reintroduced on the island and which were continuously provided with food along with other interventions, found that their population decreased by 60% over three years. No statistical tests were carried out to determine whether this decrease was significant. Four infants were born to the introduced population of 20 gibbons (reproductive rate=20%). They were fed and provided with water from artificial food and water stations. Gibbons were introduced in successive pairs into habitat that did not resemble their natural habitat and without resident gibbons. Gibbons were obtained individually from commercial animal dealers and housed in a laboratory for at least one month together with the gibbon individual with which they were released on the island. In 1961, gibbons were designated protected animals in Thailand. The study does not distinguish between the effects of the different interventions mentioned above.
Reintroduce primates into habitat where the species is present

A study, which was included in a review, in 1976–1977 in a protected forest in Thailand on captive lar gibbons Hylobates lar that were reintroduced, along with other interventions, found that their population decreased by 6% and that no infants were born in the 17 months after release. No statistical tests were carried out to determine whether this decrease was significant. One male was recaptured, removed and treated after being injured by wild gibbons. Four gibbons joined wild groups. A total of 31 gibbons were introduced. Anaesthetized gibbons were either kept in separate cages for 14 days before release, or laid on the forest floor. Injured animals were recaptured and treated. In 1961, gibbons were officially protected by national legislation. The study does not distinguish between the effects of the different interventions mentioned above.
Permanent presence of staff/manager

A study, which was included in a review, in 1976-1977 in dry evergreen forest in Sai Yok National Park, Thailand on reintroduced captive lar gibbons Hylobates lar in areas with permanent presence of area managers along with other interventions found that their population decreased by 6% and no infants were born 17 months post-release. No statistical tests were carried out to determine whether this decrease was significant. Four gibbons joined wild groups. The permanent presence of area managers and other staff appeared to ensure protection from hunters. A total of 31 gibbons were introduced as individuals, pairs, or family groups into habitat with wild conspecifics. Anaesthetized gibbons were either kept in separate cages from which they could hear, but not see each other for 14 days before release, or laid out on the forest floor. Injured animals were recaptured and treated. In 1961, gibbons were protected in Thailand. The study does not distinguish between the effects of the different interventions mentioned above.
Allow primates to adapt to local habitat conditions for some time before introduction to the wild

A study, which was included in a review, in 1976-1977 in tropical forest in Sai Yok National Park, Thailand on captive lar gibbons Hylobates lar that were allowed to adapt to local conditions before they were released along with other interventions found that their population decreased by 6% and no infants were born in the first 17 months post-release. No statistical tests were carried out to determine whether this decrease was significant. Four gibbons joined wild groups. Anaesthetized gibbons were either kept in separate cages from which they could hear, but not see each other for 14 days before release, or laid out on the forest floor. Thirty-one gibbons were introduced as individuals, pairs, or family groups and into habitat with resident wild gibbons. Injured animals were recaptured and treated. In 1961, gibbons became officially protected in Thailand. Reserve staff was permanently present. The study does not distinguish between the effects of the different interventions mentioned above.
Reintroduce primates as single/multiple individuals

A study, which was included in a review, in 1967–1970 on lar gibbons Hylobates lar reintroduced in pairs at two sites in Thailand along with other interventions found that populations decreased by 6-60% over three years. At one site the population of gibbons decreased by 60% over three years, while at the other population declined by 6%. No statistical tests were carried out to determine whether these decreases were significant. At the first site four infants were born (reproductive rate =20%), while at the second site there were no births. Before release anaesthetized gibbons were either kept in separate cages for 14 days before release, or laid out on the forest floor. At the first site, 20 gibbons were introduced into habitat that did not contain resident gibbons, while at the second site 31 gibbons were introduced in an area that contained wild gibbons. Monkeys were obtained individually from animal dealers and housed together in a laboratory for at least one month before release. Gibbons were fed supplementary food and water. Four gibbons joined wild groups. Injured animals were recaptured and treated. In 1961, gibbons were officially protected by the Thai government. Neither study distinguishes between the effects of the different interventions mentioned above.
Treat sick/injured animals

A study, part of a review, in 1976-1977 in Sai Yok National Park, Thailand found that numbers of captive lar gibbons Hylobates lar that were released and treated when injured or sick alongside other interventions decreased by 6% and no infants were born 17 months post-release. No statistical tests were carried out to determine whether this decrease was significant. One male was recaptured, removed and treated after being injured by wild gibbons. Four gibbons joined wild groups. A total of 31 gibbons were introduced as individuals, pairs, or family groups into habitat with resident wild gibbons. Anaesthetized gibbons were either kept in separate cages from which they could hear, but not see each other for 14 days before release, or laid out on the forest floor. In 1961, gibbons became officially protected in Thailand. Permanent presence of area managers and other staff appeared to ensure protection from hunters. The study does not distinguish between the effects of the different interventions mentioned above.
Reintroduce primates in groups

A study, which was included in a review, in 1976-1977 in dry evergreen forest in Sai Yok National Park, Thailand found that captive lar gibbons Hylobates lar that were partially released in family groups alongside- other interventions decreased in numbers by 6% and no infants were born during 17 months post-release. No statistical tests were carried out to determine whether this decrease was significant. Four gibbons joined wild groups. A total of 31 gibbons were introduced as individuals, pairs, or family groups into habitat with resident wild gibbons. Anaesthetized gibbons were either kept in separate cages from which they could hear but not see each other for 14 days before release, or laid out on the forest floor. Injured animals were recaptured and treated. In 1961, gibbons became protected in Thailand. Reserve staff was permanently present. The study does not distinguish between the effects of the different interventions mentioned above.