Oka / Poster

The effects of forest fires on the family of Bornean gibbons.

Teruki OKA

     The Bornean gibbon, Hylobates muelleri, is one of the most conspicuous species that characterizes the lowland tropical rainforest in Kalimantan. However, nowadays, many gibbon populations are limited in small isolated remnants and become vulnerable to local extinction. Worse still, the forest fires 1997-1998 in Indonesia, exacerbated by strong droughts related to the ENSO event, have devoured vast areas of their habitat. Here, I report how gibbons were influenced by the fire. The field survey was conducted at the Bukit Soeharto Education Forest before (December 1995 to October 1997) and after the fire (December 1998 to February 1999). As of 1997, there were 21 individuals from 6 different groups in the study area. Every group was a nuclear family based on a mated pair and highly territorial. Habitat degradation by the fire has caused disappearance of 6 individuals including 2 infants and disruption of 3 families. Home ranges of surviving groups have extended more than twice as large as they were. Furthermore, 4 pairs have come to share a large range with some small portions used exclusively in the range. The excess of cost for maintaining territory over the benefit obtained within the territory might have decreased their territorial behavior. Application of the DNA fingerprinting technique employing minisatellite hyper variable regions of DNA has revealed that there is a quite possibility of genetic relationships among these 4 pairs.