Estimates of Orangutan Distribution and Status in Sumatra

Schaik, Carel P. van; Poniran, S.; Utami, Siti; Griffiths, Mel; Djojosudharmo, S.; Setia, Tatang Mitra; Sugardjito, Jito; Rijksen, H. D.; Seal, Ulysses S.; Faust, T.; Traylor‐Holzer, Kathy; Tilson, Ronald L.

doi:10.1007/978-1-4899-1091-2_12

Cited by 17 publications

(7 citation statements)

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“…Other studies have used 0.75-0.80 where it is considered one or more of these factors are not relevant (van Schaik et al, 1995b(van Schaik et al, , 2001Russon et al, 2001). It could be argued that these reduction factors do not apply to our study as the surveys took place within identified habitat sub-types, within areas where the degree of logging disturbance was known and with the assistance of up-to-date satellite images.…”

Section: Estimating the Population Size Within The Greater Sg Sebangmentioning

confidence: 99%

“…It has been found that orangutan densities derived from nest counts compare favourably with the 'true' density (van Schaik et al, 1995a). Reasonably reliable estimates of the orang-utan population size of a large study area in Sumatra have been derived by combining densities with information on land use and vegetation cover obtained from satellite images (van Schaik et al, 1995b(van Schaik et al, , 2001.…”

Section: Introductionmentioning

confidence: 99%

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Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia

Morrogh‐Bernard

Husson

Page

et al. 2003

Biological Conservation

186

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Section: Estimating the Population Size Within The Greater Sg Sebangmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia

Morrogh‐Bernard

Husson

Page

et al. 2003

Biological Conservation

186

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“…The density of nests or nest groups was used for estimation of distribution and population density [Fruth & Hohmann, 1994;Furuichi et al, 1997Furuichi et al, , 2001aGhiglieri, 1984;Grossmann et al, 2008;Hashimoto, 1995;Mohneke & Fruth, 2008;Plumptre & Reynolds, 1996Reinartz et al, 2008;Russon et al, 2001;Tutin & Fernandez, 1984;van Schaik et al, 1995;White, 1994], and their locations are used to examine habitat use and seasonal changes therein [Anderson & Williamson, 1983;Baldwin et al, 1981;Fruth & Hohmann, 1994;Furuichi & Hashimoto, 2004;Furuichi et al, 2001b;Kano, 1992;MacKinnon, 1974;Ogawa et al, 2007]. Furthermore, the size and composition of nest groups were used to estimate the size and composition of parties of chimpanzees and bonobos or groups of gorillas, and their seasonal changes [Furuichi et al, 2001a;Hohmann et al, 2006;Schaller, 1963;Tutin et al, 1995].…”

Section: Introductionmentioning

confidence: 99%

Nest groups of wild bonobos at Wamba: selection of vegetation and tree species and relationships between nest group size and party size

Mulavwa¹,

Yangozene²,

Yamba-Yamba³

et al. 2010

American J Primatol

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We examined the location of nest groups, spatial distribution of nests within a nest group, and attributes of individual nests of wild bonobos at Wamba, Democratic Republic of Congo. We also examined the seasonal factors influencing nesting behavior and compared the nest group size with the 1 hr party size during daytime. We defined a nest group to be a cluster of nests that were built in the same evening and found within 30 m from the other nearest nest. Examination of the largest gap within a nest group suggested that 30 m was an acceptable cutoff value. Monthly rainfall or fruit abundance did not significantly influence the monthly mean nest group size. Nests were built in the swamp forest for as many as 13% observation days, suggesting the need for reevaluation of the use of swamp forest by bonobos. The use of swamp forest was influenced not by seasonal rainfall or fruit abundance, but by the fruiting of specific species. Preferred tree species for building nests accounted for 19.8% of standing trees, which suggested that the selection of sleeping sites was not largely restricted by the distribution of specific species. The mean 1 hr party size was almost identical through the day and was similar to the mean nest group size. Parties of bonobos sometimes split into smaller nest groups, especially when feeding on non-preferred fruits during fruit scarcity. By contrast, when feeding on preferred fruits while ranging in large parties, they often aggregated to form even larger nest groups. When sleeping in small- or middle-sized nest groups, they tended to aggregate the next morning. These tendencies may reflect the gregarious nature of bonobos who prefer to range or sleep together as far as circumstances allow.

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“…Most numbers, however, referred to the smaller Gunung Leuser National Park, c . 9000 sq km, which was estimated to contain between 4000 and 6000 individuals, most probably near 6000, around 1990 (van Schaik et al ., 1995b). The first estimates for the whole Leuser Ecosystem were obviously higher than those of the national park (van Schaik et al ., 1995b: c .…”

Section: Changes In the Number Of Orang‐utans In The Leuser Ecosystemmentioning

confidence: 99%

“…2, corresponding to estimates of mean densities of 3.5, 1.5 and 0.75 individuals per sq km, respectively (Table 1). This yields a total estimated number of orang‐utans (always multiplied by a 0.8 safety factor, to take into account pockets of reduced density or absence of orang‐utans caused by local hunting, unexplained unsuitability of local habitat conditions or unusually large distance from edges or rivers; see also van Schaik et al ., 1995b) of c . 12,000 for the entire Ecosystem around early 1993 (Table 1).…”

Section: Changes In the Number Of Orang‐utans In The Leuser Ecosystemmentioning

confidence: 99%

Dramatic decline in orang-utan numbers in the Leuser Ecosystem, Northern Sumatra

Schaik

Monk²,

Robertson³

2001

Oryx

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The Leuser Ecosystem, northern Sumatra, Indonesia, contains the world’s largest orang‐utan Pongo pygmaeus population. We examine the consequences of the recent wave of forest conversion, and legal and illegal logging, on orang‐utan numbers in the Leuser Ecosystem. We review density variation inside the Leuser Ecosystem and its causes, and the consequences of selective logging, exhaustive logging and clear‐felling for habitat conversion on orang‐utan densities. The analysis of the orang‐utan’s decline is based on information on forest loss, logging intensity, and the delineation of logging concessions and legal changes in land use status. The results indicate a very rapid decline, by c. 45 per cent, from c. 12,000 in early 1993, over a 6‐ to 7‐year period. During 1998 and 1999, losses occurred at a rate of about 1000 orang‐utans per year. At this rate, further losses in the near future are expected to put the survival of Leuser’s orang‐utans in serious doubt.

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Estimates of Orangutan Distribution and Status in Sumatra

Cited by 17 publications

References 0 publications

Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia

Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia

Nest groups of wild bonobos at Wamba: selection of vegetation and tree species and relationships between nest group size and party size

Dramatic decline in orang-utan numbers in the Leuser Ecosystem, Northern Sumatra

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