The Research On Singing Behavior Of Eastern Black Crested Gibbon (nomascus Nasutus)

The eastern black crested gibbon (Nomascus nasutus) was considered to has been extinct from China before it was rediscovered in Bangliang, Jingxi County, Guangxi in 2006. Little was known about its behavior and ecology. We studied the singing behavior of three groups of gibbon from August 2008 to October 2009 at Bangliang Nature Reserve, to investigate the character, function and influence factors of singing. The main methods and results were summarized as follows.(1) Sony TC-D5 Pro2 recorder and Sony C-76 directed microphone and Sony tape were used to record the singing bouts of gibbons. Signal/RTS 4.0 was used to analyze the sonogram of the bouts which have good quality. The results showed that the frequency of sonogram was very high, it tended to or exceeded 4 kHz. The adult males produced 1-15 aa notes and 2-7 modulated figures. Adult females produced stereotyped sequence named great call. Adult male and females in the same group coordinated to produce complex sequence named duet. The duets usually started and ended by adult males. Adult males produced solo bouts when females kept silence when they were singing.(2)The data of sunrise, singing group, the type of singing (duet, solo), starting and ending time, starting time of great calls were recorded in 228 days. The results showed gibbon groups tended to sing in the early morning. Most (91.4%) of singing bouts occurred between half an hour before and three hours after the sunrise, and 53.1% occurred one hour after the sunrise. Groups sang on average 69.7% of days monitored, and sang an average of 1.24 bouts per singing day. The average duration of the singing was 18.3 minutes, and females produced 4.4 great calls during one duet bout. There was no significant difference in the duration, but there was significant difference in the frequency of singing and number of great calls among groups.(3) Neighboring groups tended to sing on different days. Singing bouts could elicit the sing of the neighboring groups if they were close. Singing bouts were supposed to adjust inter-group spacing in some days, but just indicated the territory occupancy of the established group in other days. Then used the occurrences sampling to collect data of behavior of neighboring groups when distance less than 300m, the results showed that it was very easy to arise the territorial conflicts and the great call of female.(4) Instantaneous and scan sampling was used to collect data of feeding. Gibbon diet comprised of fruit (54.2%), leaves (18.8%), buds (16.8%), invertebrate animals (5.6%), follower and other(4.5%). There was marked seasonal variation in gibbon diet. The frequency of singing and number of great calls will change with seasonal variation in food availability. The frequency of singing and number of great calls will higher during fruit season. This show that the singing behavior maybe protect the food resources.(5) We analyze the difference of singing behavior at different meteorological factors. The resulted show that meteorological factors, including illumination intensity, rainfall at night and in the morning, wind speed, posed significant effects on gibbons'singing behavior. Gibbons called later relative to sunrise in foggy days than in cloudy days and sunny days. They produced shorter bouts and called later in rainy days. On the contrary, gibbons produced longer bouts and called earlier in windy days than in other days. No significant effect of temperature on the singing behavior was detected.