NESTING BEHAVIORAL ADAPTATIONS OF ORANGUTAN (PONGO PYGMAEUS MORIO) IN COAL MINING AREA IN EAST KALIMANTAN

Coal mining changed forest structure and composition, it caused large negative impacts on the orangutan. In order to mitigate those negative effects, it is crucial to understand their nesting behavior adaptation in mining area. We investigated 74 times nested event in coal mining rehabilition area (CMRA) in East Kutai and 123 times in the Kutai National Park (Prevab) from October 2013 to September 2014 and include only night nests. We compared both habitats. Orangutans in CMRA built the nest later than in Prevab and used 15 species of trees as nests sites intensively on Senna siamea and Gmelina arborea. In Prevab, 35 species with the higher frequencies on Eusideroxylon zwageri and Dracontomelon dao. The average diameter of nest trees in CMRA smaller than Prevab. The height of nest trees in CMRA with the highest frequency was in 10.1-15 m, while in Prevab was as in 20.1-25 m. Orangutans in CMRA nested at the height of <15 m, lower than in Prevab was >20 m. Reused nest in CMRA was higher than in Prevab. Orangutans in CMRA more often built nests at the peak and limb, while in Prevab at the limb and peak. Orangutans in CMRA had learned to utilize various species and dimensions of trees as the place to build nests.


INTRODUCTION
The great apes build night nests exclusively on the trees (Tutin & Fernandez 1984;Hall et al. 1998;Poulsen & Clark 2004). Theoretically, one of their reasons establishes it is an anti-predators strategy (Anderson 2000). The natural predator of Bornean orangutan that has been reported is Neofelis diardi (MacKinnon 1974;van Schaik 1983). Other motives are to avoid contact with nocturnal frugivores (Anderson 2000), to comfort sleep (Stewart et al. 2007), to better sleep quality (Anderson 1998), and as an anti-vector of diseases (McGrew 2004). The nest structure is important to increase the security of great apes during sleeping (Baldwin et al. 1981).
Orangutans built nests every day and become a reliable indicator of their existence in an area (MacKinnon 1974;Ancrenaz et al. 2004;Morrogh-Bernard et al. 2009

Procedures
The monitored parameters of orangutans' nesting behavior in this research were: (a) time duration of making nest; (b) characteristics of nest trees consisting of species, tall, and diameter; (c) nest characteristics such as the nest high from ground level, nest protection by tree canopy, nest position on the tree, and nest type.
The nest protection by tree canopy was distinguished becoming a closed nest and opened nest. Further, the nest position on the tree followed a classification of Prasetyo et al. (2009) dividing into four positions of nest namely (1) locating on the axilla and center of branches; (2) edge of branches; (3) top of tree; (4) two or more trees; and (0) on the ground level (Figure 4.1).The built nest of orangutan was classified into two types such (1) new nest: the orangutan built new nest using fresh materials of branches/limbs/leaves/others; (2) reused nest: the orangutan reused the old nets either repairing or without any reparation. Orangutan usually repaired the old nest by adding fresh leaves or limbs. The nest can belong to both the same individualand other individuals.

Data analysis
A descriptive analysis utilizing average, range, and percentage, was used to explain the starting time and duration of building the nest, species of the nest tree, tree dbh (diameter at breast height) of nest, tree high of the nest, nest high from ground, nest position on the tree, and nest protection by tree canopy. The analysis results then were presented in graphics and tables.
A non-parametric statistic test of Mann-Whitney was applied to observe the nesting behavioral differences among the orangutans living in the CMRA and Prevab (Sugiyono 2007). The species similarity index Srensen ( ) was used to determine the tree species similarity of orangutan nests between both habitats. A, B, and C are the Nesting Behavioral Adaptations Of Orangutan… (Ningsih, et al) [101] This work is licensed under a Creative Commons Attribution 4.0 International License number of nested tree species in the CMRA, Prevab, and both habitats, respectively (Curtis 1959). Figure 2. Classification of orangutan nest location on trees (Prasetyoet al. 2009).

Result
The orangutans in the CMRA begin building nests in an average of ±33 minutes before sunset namely at 5.39 pm at Central Indonesia Time (between 2.54 pm and 7.02 pm). In Prevab, they started establishing nests in an average of 55 minutes before sunset namely at5.21 pm at Central Indonesia Time (between 5.14 pm and 6.38 pm).
The orangutans in the CMRA and Prevab need times in an average of 6.7 minutes and 6.5 minutes to finish their night nest structures, respectively. The analysis results of Mann Whitney denote an insignificant difference of orangutans in both habitats (N: 196; P 0.903 > 0.05).

Tree characteristics of nest
We identified 15 trees species that used by orangutans as nest trees in the CMRA. Johar (Senna siamea) and gmelina (Gmelina arborea) possess a high frequency of uses namely 43.42% and 26.32%, respectively. Figure 3 presents the female orangutans with her baby built a nest on johar and gmelina. The nest tree species and frequency of use conducting by the orangutans in the CMRA can be seen in Figure 4.  In Prevab, about 35 identified tree species are utilized by orangutans as their nesting place and only 7 species of them possessing frequencies of use more than 5%. Tree species like Borneo ironwood or ulin (Eusideroxylon zwageri), sengkuang (Dracontomelon dao), and Bayur (Pterospermum spp.) are frequently utilized by orangutans as their nest trees with frequencies of use consisting of 15.45%, 13.01%, and 12.20%, respectively ( Figure 5).  The analysis result of Man Whitney regarding the tree dbh differences of orangutan nests indicates a significant difference between these two habitats (N: 147; P 0.000 < 0.005). The nest tree dbh distribution of both habitat types is characterized in Figure 6.     Table 1). Orangutans at CMRA choose more often building their nests on a position of 3/ shoots of trees than other positions. This is manifested by a high frequency of nesting at this position (63.51%), then followed by a position of 2/edge of branches (27.03%), a position of 4/two trees or more (5.41 %), and a position of 1/main branches (4.05%). At Prevab, the orangutans set more often their nests on a position 2 (51.67%), position 3 (36.67%), and position 1 (11.67%). The frequency of choosing nest position for orangutans in both research locations is presented in Figure 9. Sites-2:

nest protecting by tree canopy in the Prevab area of Kutai National Park is not available, as a comparison, we used the research results of Niningsih (2009).
Figure 9. Frequency of selected of nest-sites location on trees by orangutans at CMRA (N = 74) and Prevab (N = 120).

Characteristics of nest trees
At Prevab, ulin was the most frequently used as a nest tree, even though, this species was not a dominant tree in the Prevab. This finding is similar to the research results conducting by Niningsih (2009) Ancrenaz et al. (2004) in Kinabatangan, showing, though, many species used by orangutans as nest tree, however, ulin was the favorite nest tree.

in Prevab and
At CMRA, orangutans live on existing tree species as their nesting places. Anyhow, there are some species seemingly is more preferable and some others are not favorable even though available in enough number. Sengon (Falcataria moluccana) and johar (Senna surattensis) are dominant trees enough at CMRA (Niningsihet al. 2017), but the frequency of using these tree species as nests were low. In vice versa, gmelina (Gmelina arborea), although, in a relatively small number and is not evenly distributed in the CMRA, however, its frequency of use as a nest tree by the orangutans is higher than sengon and johar. The gmelina, at the same tree, has been observed that this tree is utilized by one of the orangutans (Clara) as many as three times and two of them are the reused nest in seven days of observation. Almost every gmelina trees at CMRA is occupied by at least more than two orangutan nests. This tree species is strongly thought to be a favorable nest tree of orangutans in the CMRA (Figure 10).
The botanical plot analysis in the CMRA showed that this area is measly discovered largediameter trees . This condition explains why the orangutans in this area more frequently making their nests on small-diameter trees (dbh ≤ 20 cm).
The botanical plot analysis in the Prevab denoted that the number of trees decreases with increasing tree diameter size (Niningsih et al. 2016). That is one of the climax natural forest structure characteristics in Borneo (Meyer 1952). Trees with a smaller diameter (dbh ≤30 cm) are found in a more amount than the larger diameter in the Prevab of Kutai National Park, but the most frequently used by orangutans as their nest places are trees with a diameter of ≥30 cm. The research results of Ancrenaz et al. (2004)

Characteristics of Nests
The findings at CMRA indicate that the nest height average of orangutans from the ground level is lower than the Prevab one. Orangutans in this location frequently build their nests on a height of <20 m, even their nesting frequency on the height of <10 m is high enough (±30%). In a natural habitat, majority of orangutans are discovered on a height range of 10 and 30 m in a tree middle layer and their nests are measly built on high young trees, for instance, the research conducted by MacKinnon (1974) in Ulu Segama,  Ancrenaz (2006) in Kinabatangan Sabah, and Sugardjito (1983) in Ketambe. The upper canopy layer locating above the nests is perceived as contributing to extra protection to the orangutans during sleeping from direct sunlight and/or raining (Ancrenaz et al. 2004). Figure 12 presents a percentage comparison of orangutans' nest height at CMRA with nest heights in some natural habitats. Figure 12. Percentages of height distribution of nests at CMRA (this study), Kinabatangan/KOCP (Ancrenaz et al. 2004), Ulu Segama (MacKinnon 1974 and Sumatera (Sugardjito1983).
Orangutansat CMRA set their nests on a lower height namely on the height of <20 m following of the available high trees distribution in this area. This hypothesis is proven by a positive correlation between the nest height of orangutans and nest tree height (N = 60; P = 0.00) (Figure 13).

Figure 13. Distribution of nests height (-■-) and height of orangutan nest trees (-♦-) at CMRA
At CMRA, a large number enough of nests are found with a height of <5 m, however, they do not belong to the observed orangutans. During the field observation, the nests were found on the ground level also, but they are not recognized as the night or day nests. This condition exhibits that during no observers, orangutans in the CMRA sometimes build their nests on smaller trees than the even observed directly (Figure 14). The number proportion, of opened nests in the CMRA, reaches 82.67%, is higher than the Prevab which is only 39.7% (current research) and in Bhirawa exceeding 50.0% (Niningsih 2009). This percentage difference is due to the different habitat of both research locations (Figure 15). Prevab is a habitat with good conditions where the vertical and horizontal forest structures are still complete (Niningsihet al. 2017), therefore, some nests locating at limb edges and treetops are still protected by other trees from both the side and above. Reversely, the habitat in the CMRA is dominated by young trees with tend evenly dimension (Niningsihet al. 2017), accordingly, there is not any canopy protection for the nests situating on the treetops and branch edges.
The wild orangutans build their night nests every afternoon or dusk as their resting places in the night. In common, orangutans build their new nests, but occasionally they also repair their old nests as sleeping locations. The research results in some different locations point out that a proportion of using the reused nests by orangutans is higher in the disturbed habitat. A research conducted by Rayadin and Saitoh (2009)  The frequency of use tree top position as a nest at CMRA was higher than the natural habitat. Selecting this position is surmised due to the small-diameter trees with small ramification is the most dominant at CMRA .
Orangutans tend to choose strong tree parts as supporting their nest structures, commonly a large branch or a group of stable branches, branching branches, or stable gap (van Casteren et al. 2012). Also, the surrounding weaker and flexible branches are used to accomplish the nest construction (forming a base and mattress) and often are completed by leaves and herbs.
Locations of nests on trees are surmised relating to the profile of trees situating in the forest. Selecting the middle and axilla branches in the natural habitat by the orangutans is expected due to those parts are available strong supports for the construction of nests that can hold weights of orangutans, especially on trees with narrow canopy profiles like the young to middle age of ulin. On larger trees with wider canopy and big branching as well as maybe the branch edges are suitable and strong enough as a support of the nest construction. In addition, the middle and axilla position of branches also contribute to protecting the orangutans from rain and sun exposures if the nest is not protected by other higher tree canopy layers.
Last, orangutans at CMRA adapted to build nests on varied species and dimensions of trees. They established more frequently nests on the treetops, and the proportion of reused nests was higher than orangutans in the natural habitats.

CONCLUSION
In conclusion, habitat changes in CMRA have encouraged orangutans living in the area to adapt one of which is in terms of nesting behavior. Orangutans at CMRA adapted to build nests on varied species and dimensions of trees, including small trees. The proportion of reused nests by orangutan at CMRA was higher than orangutans in the natural habitat and they established more frequently nests on the tree tops.