Sumatran orangutan (Pongo abelii)
Mohamed bin Zayed Species project number 162512549
Intensifying post-release monitoring of a newly reintroduced Sumatran orangutan population at Jantho Nature Reserve, Indonesia
Reintroduction is listed as the 2nd of 5 key objectives in the Indonesian Orangutan Conservation Action Plan (Soehartono et al. 2009). Whereas post-release monitoring is one of the most important, yet often under-supported, facets of reintroduction programmes (Beck et al. 2007) - allowing for the evaluation of success and identification of aspects that may need improvement. Many orangutans released in Jantho begin their new life exploring the forest near the release site, gradually extending their range. Whereas some immediately disperse and settle further afield, seldom or never returning. Still others explore the local area for months, only to suddenly establish home ranges elsewhere. Hence, if monitoring originates near the release point the chance of encountering every orangutan is low. Of the 81 individuals reintroduced in Jantho since April 2011, 30 have not been seen in the past 12 months or longer, with field teams on average encountering 14.4 different individuals per month (Nowak 2014). With the number of reintroductions still increasing, along with the numbers of ex-captives being rehabilitated, the capacity of post-release monitoring correspondingly needs to increas
Orangutans are cryptic and can be difficult to find in a forest setting - an issue not limited to reintroduction programmes, but also experienced in field research programmes studying truly wild orangutans. Orangutans also travel alone or in small groups and have large home ranges, up to 1,500ha for females and possibly over 10,000 ha for males (Buckley 2014, Singleton and van Schaik 2001). Until now our understanding of both wild and reintroduced populations has been largely limited to observations within clearly demarcated but limited study areas, mostly averaging only around 400 hectares in extent, with searches and follows emanating from a single basecamp.
We therefore plan to base field teams further afield, in remote areas of Jantho to encounter individuals that have dispersed and settled there to gain a better understanding of their survival, behaviour and ecology, and the dynamics and dispersal of newly established populations, that will have ramifications for similar projects in Sumatra and Borneo.
In addition to creating a new, viable orangutan population, we also wish to formulate a new protocol for other sites to replicate. This will help to strengthen field conservation initiatives and inform policies and land-use planning decisions, through an improved understanding of biodiversity needs. Furthermore, the findings will be extremely useful for a forthcoming orangutan PHVA workshop planned for 2016.