Effects of meteorology, astronomical variables, location and human disturbance on the singing apes: Hylobates albibarbis

Abstract

Gibbons are characterized by their species-specific calls. The frequency of singing is known to be affected by rainfall, with singing occurring less in the wet season. I investigate the hypothesis that gibbon singing is also affected by the natural light-dark cycle, and by the changing light intensity and air quality resulting from the smoke haze which blankets the Indonesian island of Borneo on a yearly basis. I compare three singing variables-onset of singing, average duration of singing bout and number of female great calls produced during the dry season of 2006 when there was no smoke haze (June-August) and when there was smoke haze present (September-November). I present evidence which indicates that the changes in singing behavior are affected by changes in rainfall and smoke intensity but not by other meteorological factors (i.e. wind and light intensity) or changing astronomical cues (light intensity, month, time of sunrise, time of moonrise, nocturnal illumination index, day length and night length). The possible long-term effects of this on gibbon behavior and territoriality are discussed. The need to carry out more research on the long-term effects of the smoke haze on wildlife behavior and possible solutions to the problem are discussed.

VARIASI STRUKTUR VOKALISASI OWA JAWA (Hylobates moloch Audebert, 1798) DI HUTAN LINDUNG PETUNGKRIYONO, PEKALONGAN, JAWA TENGAH

“…Topografi dari hutan lindung Petungkriyono yang berbukit-bukit juga bisa membiaskan gelombang suara. Cheyne (2008), menyebutkan bahwa satwa sangatlah sensitif terhadap perubahan lingkungan sehingga dapat berpengaruh terhadap perilaku satwa tersebut. Faktor meteorologi seperti hujan dan angin berpengaruh signifikan terhadap perilaku bersuara dari Hylobates albibarbis.…”

“…Berdasarkan fakta dilapangan, pagi hari setelah terjadinya hujan, terdapat beberapa kelompok Owa jawa (N=2 di LPs 2) tidak melakukan vokalisasi, sedangkan kelompok yang lainnya tetap melakukan vokalisasi dengan waktu permulaan bersuara yang tidak seperti biasanya. Hal tersebut sesuai dengan studi yang dilakukan oleh Cheyne et al (2008), yang menyebutkan bahwa Owa cenderung akan mencari makan dibandingkan dengan melakukan vokalisasi untuk menandai daerah teritorial. Owa jawa akan mengalami kehilangan panas tubuh selama hujan berlangsung saat malam dan membutuhkan banyak energi untuk menormalkan suhu tubuhnya.…”

A Comparison of Hylobatid Survey Methods Using Triangulation on Müller’s Gibbon (Hylobates muelleri) in Sungai Wain Protection Forest, East Kalimantan, Indonesia

“…Each team was in place between 04:30 and 05:00 h, and data collection began when the first gibbon group started singing and continued until all groups had stopped for 30 min Hamard et al 2010). We did not restrict data collection to a single time slot because there is no peak calling period for Bornean gibbons and the triggers for them to start and stop singing appear to be behavioral rather than external (Cheyne 2008;Harrison 2011). Although gibbons may sing after 30 min of silence, this behavior represents <2% of all singing bouts and is often associated with a territorial conflict or interaction with another species (Cheyne unpub.…”

“…The proportion of a groups calling on any given day can vary depending on gibbon density and climatic conditions (Cheyne 2008;Maples et al 1988). In addition, gibbons may not call every day even if no adverse climatic conditions are in effect (Brockelman and Srikosamatara 1993).…”

Sleeping Site Selection by Agile Gibbons: The Influence of Tree Stability, Fruit Availability and Predation Risk

“…The altitude is about 10 m above sea level, and the whole area is about 5,300 km 2 with the core study area consisting of 9 km 2 . Temperature averages 26 ° C (range 18-38 ° C) and rainfall averages 232 mm/month (range 4-532 mm [Cheyne, 2007[Cheyne, , 2010Harrison et al, 2010]). There is a pronounced seasonality in temperature and food availability, both of which fluctuate between wet and dry season [Cheyne, 2010;Harrison et al, 2010].…”