The lack of interaction may be due to the small number of social partners available. Male and female adults are, more or less, social equals. In one study, the male was found to groom the female more often and play with the young more frequently. Too few studies have been conducted to determine if this behavior is common to all groups of Hylobates muelleri . The call of the gray gibbon has been studied in detail.
Adult males sing long songs before sunrise.
The duets average 15 minutes and occur on a daily basis. Lone males sing longer songs than paired males, possibly to attract mates. The gray gibbon lives in tropical evergreen and semi-evergreen rain forests. Hylobates muelleri as a near threatened species. The gray gibbon is on the threatened species list due to logging practices on Borneo.