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Primate Conservation 2019 (33): 6 pp.
Tree Climbing Methodology for Orangutan Conservation
Judah M. Epstein1 and James Reed2
1Department of Math and Science, Brookhaven College, Farmers Branch, TX, USA
2Tree Monkey Project, San Rafael, CA, USA
Abstract: Habitat loss, poaching and the pet trade have resulted in thousands of orangutans being rescued and taken to rehabili-
tation centers, many of them infant or juvenile orphans. Besides caring for them, the goal of these centers is to train them for
release back into the wild, and critical to the success of post-release survival is their competence in moving through the forest
canopy. Orphaned orangutans need regular practice at tree-climbing in order to prepare them for their future life in the wild.
Training for this is lacking at rehabilitation centers, however, because caregivers engage with the orphaned orangutans largely on
the ground. Orangutan rehabilitation can be greatly improved by training orangutan caregivers in a standardized and safe method
of tree climbing so that they can encourage and accompany orangutans to spend more time in the trees. Caregivers trained in
tree climbing can also help in wild orangutan rescues, in center maintenance and, through arboreal data collection, in scientic
research. We discuss the practical solution of implementing a standardized tree climbing method to orangutan caregivers. Pro-
fessional climbers have volunteered with the nonprot Tree Monkey Project to teach orangutan caregivers in Bornean Indonesia
and Malaysia. The tree-climbing training program has been successful in allowing caregivers to climb trees alongside orphaned
orangutans, encouraging the orangutans to increase the time they spend in the trees and allowing them to hone their agility and
skills in moving about in them.
Key words: Orangutan, tree climbing, rehabilitation, arboreal locomotion
Introduction
Orphaned orangutan post-release survival is substantially
dependent upon their receiving proper training at their rehabil-
itation centers. It is vital that they be prepared for an arboreal
life, yet orangutan training at rehabilitation centers is largely
at ground level or only limited heights above the ground. A
survey of survival rates from reintroduction showed that it
ranges from 20% to 80%, providing a realistic average of
40% successful survival (Russon 2009). One of the critical
skills determining survival is competence in travelling in the
tree canopy to explore their home range, to make nests to rest
and sleep in (Descovich et al. 2011) and, most particularly, to
nd food sources (Rosen and Byers 2002) and have the agility
and skill to reach and feed on them (Russon 2002; Descovich
et al. 2011). It has been shown that captive orangutans that
build complex nests for a more comfortable sleeping environ-
ment sleep better (Samson and Shumaker 2013). Enhanced
arboreal skills enable orangutans to build more complex nests,
and nests higher in the canopy where they are better protected
from tigers (Riedler et al. 2010).
Common practice at orangutan rehabilitation centers and
their forest schools is for the human caregivers to interact with
orangutans while at ground level where the humans are most
comfortable. Caregivers may also encourage the orphans to
explore constructed wooden jungle gyms of limited height.
Much better would be to have the caregivers climb the trees
and/or rest on arboreal platforms. This would encourage the
orangutans to follow their mother substitutes to higher up in
the trees, and thus make them exercise better their natural
climbing abilities. The climbing technique for human care-
givers we describe here is synthetic-rope-supported access to
the canopy. The aim is not to teach locomotion techniques
to orangutans but for the caregivers to get up into the canopy
and encourage and motivate the orangutans to follow them,
navigating the trunks, branches and lianas to acquire and
practice the necessary skills. Climbing towers and canopy
decks should be constructed if there are insufcient or no
trees in the training areas.
There are other advantages to tree climbing competency.
Staff could use the skill to improve the rehabilitation center’s
outside facilities through maintenance such as trimming trees
Epstein and Reed
2
around enclosures and pens to keep animals from escaping.
When forests are being clear-cut for oil palm plantations or
being degraded and fragmented by logging and mining opera-
tions, orangutans are often stranded and unable to escape, and
personnel from orangutan rehabilitation and rescue organiza-
tions are then asked to rescue them. Rescuers dart the orang-
utan and are generally able to catch it in a net as it falls, but
sometimes, the drugged orangutan becomes stuck in the tree,
and a rescuer then has to climb up, without safety equipment,
to release it (IAR 2015). Technical tree-climbing techniques
using ropes, harnesses and the appropriate equipment would
benet rescuers in safely retrieving and rescuing orangutans.
A safe method for climbing trees would enable expanded
and improved research on the ecology of orangutans. Moni-
toring orangutan numbers and distribution could be more
precise if there were better measures of nest decay. Current
research relies on ground and aerial surveys (Ancrenaz et al.
2004) and getting close up to the nest would yield more accu-
rate results. Access to canopy nests could allow for research
on long-term stress levels of orangutans. The Department of
Biopsychology at the Dresden Technical University in Ger-
many has a laboratory that analyzes hair cortisol, the primary
stress hormone and a crucial indicator of animal welfare and
survival. Hair taken from captive orangutans has yielded
cortisol data correlated to stress levels, showing stress his-
tory over several years. Yet the department has not collected
hair cortisol data from any wild or reintroduced orangutans
(Carlitz 2016). Technical tree climbing could enable access
to wild nests to directly retrieve hair samples for examining
stress history and for genetic analyses. Hair samples from
nests could identify reintroduced orangutans, contributing to
monitoring their ranging and survival and, as indicated by
Houle et al. (2004; p.237), “primate ecological studies can
benet from accessing the canopy to estimate intra-tree and
inter-tree variation in food availability and nutrient value,
patch and subpatch depletion, foraging efciency, as well as
nest structure and nesting behaviors, parasitic transmission
and predator detectability.”
A way to enhance orangutan rehabilitation, rescue, and
scientic research is to train orangutan caregivers and conser-
vation staff in safe, technical tree-climbing methods.
Tree-climbing Courses
Modern tree-climbing methodologies and reliable climb-
ing gear are already available. Using climbing methods
derived from those of arborists, rock climbers, and speleolo-
gists (Houle et al. 2004) allows for access to the tree canopy
for scientic research and data collection (Lowman and Whit-
tman 1996). We have given courses to orangutan caregiv-
ers during four trips to Indonesia and Malaysia—early 2016,
early 2018, late 2018, and early 2019 (Fig 1). The instructors
completed ofcial training from Tree Climbing International
(TCI) and/or had signicant eld experience in the arborist
industry. The methodology these instructors taught to the
orangutan caregivers is the standard method used by TCI,
which is intended for recreational tree-climbing purposes.
The recreational method provides climbers with a simple
and basic system to climb trees and maneuver within them.
More advanced techniques used by experienced professional
arborists for large limb removal, arboreal chainsaw work, and
for the use and maintenance of a much larger assortment of
equipment are not necessary for initial training and tasks for
orangutan conservation. The basic recreational method is
quicker to learn, simpler to remember, and has less equipment
involved. Members of the Tree Monkey Project have found it
to be fully suitable for the orangutan caregivers to accomplish
and safely succeed in the conservation tasks discussed in this
article. We emphasize, however, that this article is not an
instructional climbing manual. A multi-day, hands-on climb-
ing course supervised by experienced instructors is essential
to achieve safe climbing practices. Here, we simply provide
a basic overview of the methodology we have taught.
The climbing courses taught by the Tree Monkey Project
instructors to the orangutan caregivers consisted of about ve
full days of eld instruction. The rst day begins with an
introduction to the environment and the gear. Each orang-
utan conservation organization was given one or two, full
sets of climbing gear (donated by the Tree Monkey Proj-
ect), consisting of arborist climbing rope with a storage bag,
auto-locking carabiners, additional gear carabiners, an arbor-
ist climbing saddle (harness) with side D rings for ipline
attachment, ipline, lanyard for foot ascent, mechanical foot
ascender, helmet, throwline cube with throwline, throwline
bag with throwline, throw weights, slingshot on six foot pole,
gloves, and a whistle (Fig. 2). All gear provided was new,
certied climbing equipment. The students were told that if
replacement gear is required in the future, then it is manda-
tory for arborist climbing rope, carabiners, arborist climbing
saddle, and helmet to be purchased as new certied climbing
Figure 1. Judah Epstein teaching tree climbing to orangutan caregivers.
Photograph by Jim Cairnes.
Tree climbing to help orangutan orphans
3
Figure 2. Tree-climbing gear provided to orangutan rehabilitation centers.
Photograph by Judah Epstein.
equipment. Climbing equipment that is used or not certied
for climbing is not authorized for use. Students were also
instructed to wear boots for footwear. They were familiarized
with the gear and proper gear inspection such as checking for
cracks, fraying, worn materials, and cuts. All climbing gear
has to be inspected prior to each use to ensure that it is clean
and in suitable condition. After each use, all gear has to be
cleaned and dry before properly storing.
Next, the site environment is inspected for hazards such
as power lines, structures, and other hazards or fallen trees
near the tree. The ground below the tree is inspected for
indications of tree health, such as root are, soil mounding,
and standing water, and the tree is carefully checked for its
health and the possibility that it presents personal hazards—
the natural strength of the species, poisonous vines, insects,
animals, cracks and splits, bark, fungus, rotting, dead and
weak branches, and potentially falling branches. When the
gear, the environment, and the tree are approved for scaling,
the team then develops a climbing plan and begin setup for
tree entry. The students are instructed with details regard-
ing anchor (branch) selection, considering tree type, angles,
branch union placement, and minimum diameter.
The climbing method taught is the Double Rope Tech-
nique (DRT). The students learn and practice the series of
knots on the rope to setup the DRT system. Safety knots are
always employed. The same system is used for ascent and
descent. Such uniformity, with no modication to the system
to switch between ascending and descending, increases
safety and enables more ease and condence to novice, and
advanced, climbers. Upon sufcient repetitions to practice
the basic climbing techniques, the students’ progress to more
advanced climbing and maneuvering while in the canopy.
They employ the same skills learned on the ground, but now
implemented while in the tree. The climber learns to analyze
and set a new anchor high up in the tree while connected to the
initial anchor until the new anchor system has been veried,
fully weight tested, and with safety knots tied. Students also
learn to maneuver within the trees and among the branches,
while maintaining a safety connection to the main anchor and
possibly an additional line. Students learn to limb-walk along
the branches. They primarily climb the rope to summit the
canopy, but the branches can also be used for summiting and
exploring through the height and width of the tree. They can
even transfer to an adjacent tree. With the help and in-tree
supervision of the Tree Monkey Project instructors, students
climb various trees to experience and overcome the different
challenges presented by each.
Courses given—2016
The Tree Monkey Project completed four climbing train-
ing courses to staff of eight conservation centers. The courses
were not held in orangutan rehabilitation centers, and the Tree
Monkey Project instructors did not meet with orangutans. In
February and March of 2016, Tree Monkey Project personnel
traveled throughout Borneo instructing staff of the following
centers.
• The Orangutan Project: Matang Wildlife Center,
Kuching, Malaysia
• Bornean Sun Bear Conservation Center (BSCC):
Sepilok, Malaysia
• Tabin Orangutan Rescue: Sepilok, Malaysia
• Borneo Orangutan Survival (BOS), East
Kalimantan Orangutan Reintroduction Pro-
gram: Balikpapan, Indonesia
• Kawasan Wisata Pendidikan Lingkungan Hidup
(KWPLH): Balikpapan, Indonesia
• Pro Natura Foundation, Sungai Wain National
Forest: Balikpapan, Indonesia
• Borneo Orangutan Survival (BOS) / Orangutan
Tropical Peatland Project (OUTrop): Nyaru Men
teng Rescue Center- Palanka raya, Indonesia
• International Animal Rescue: Ketapang, Indonesia
Courses given—2018-2019
In February 2018, October 2018, and April 2019, we
returned to the area of Balikpapan, East Kalimantan, Indonesia,
specically to train orangutan caregiver staff of Jejak Pulang,
an Indonesian foundation supported by Four Paws Interna-
tional, Vienna, Austria (<https://www.four-paws.org/>). Ini-
tial training was provided to new students (February: ve;
October: ve). Returning students (same as in February, plus
one from KWPLH of 2016) received advanced training of
split tail and ip line, which are techniques for maneuvering
in the tree, along branches as well as up and down branches
to reach higher and lower positions, and spiking which is a
technique for ascending without using a high anchor. They
were also given demonstrations of pruning and limb removal.
The April 2019 course consisted of initial training to four new
students, while returning students received advanced training
of aerial rescue and the Single Rope Technique (SRT).
Epstein and Reed
4
Considerations Regarding the Courses and Methods
Taught
The two main methods of tree climbing with ropes are
Double Rope Technique (DRT) and Single Rope Technique
(SRT). The original plan of the Tree Monkey Project was
to instruct all students rst in DRT and then in SRT, within
one week. During the rst instructional week session in
2016, students successfully learned DRT and then progressed
to receive initial instruction in SRT. Students had dif-
culty learning and achieving condence with SRT because
of the additional complexities of the mechanical equipment
and varied method of ascent and descent, as compared to
the simpler knot method of DRT. To maximize safety, the
Tree Monkey Project leadership decided to discontinue SRT
instruction for the initial one-week training sessions. The
time that would have been allocated to SRT instruction tran-
sitioned to additional DRT practice, condence building and
maneuvering skills in the canopy. In April 2019, SRT was
successfully instructed to returning students, after they had
had months of DRT self-practice.
The expedition in 2016 trained dozens of climbers of
several rehabilitation centers. Each center was left with a
complete set of climbing gear. From most centers, either no
climbing feedback had been received, or feedback of no ongo-
ing climbing due to various reasons such as employee attri-
tion of the trained climber. Positive feedback was received
from KWPLH in Balikpapan, Indonesia, as one climber in
the 2016 training returned for advanced training to both of
the courses in 2018 with Jejak Pulang. This climber was very
enthusiastic and has climbed often since the initial training in
2016. KWPLH is a center for Sun Bears, so this climber has
used his abilities for center maintenance but not for orangutan
rehabilitation.
The 2016 courses introduced the methodology through-
out the island of Borneo as an innovative method to help
orangutans improve their skills in moving about in the trees,
and set the stage for success when reintroduced. While the
2016 courses may have had minimal direct impact towards
the training of orangutans, the 2018 and 2019 courses have
already made progress in this sense. The success of the 2018
and 2019 courses was in large part due to the Tree Monkey
Project closely interfacing with the onsite leadership of Jejak
Pulang, Dr. Signe Preuschoft, and the rehabilitation coor-
dinator Nur Aoliya. The onsite leadership and scientists
experienced the eld training to understand the process and
requirements. The leadership made the decisions regarding
implementing forest school methods and adapting to the new
procedures. Jejak Pulang is a relatively small rehabilitation
center, which began operating only in 2017, and the lead-
ership is more open and exible to innovative methods for
orangutan rehabilitation. The center currently houses only a
small number of orangutan orphans with a focus solely on
rehabilitation. These attributes have enabled Jejak Pulang’s
initial success in implementing tree climbing at its forest
school. The caregivers climb trees and the orangutans follow
alongside their surrogate mothers, ascending to the canopy
(Winter 2018). Caregiver climbing with orangutan orphans
has been limited to infants of about 2 years of age, with high
learning and high re-introduction potential (Figs. 3 and 4).
The 2016 training courses were marked by minimal inter-
action and rst-hand climbing experience with the leadership
of each organization. The instruction focused on the tech-
nique of climbing to the individual conservation staff. There
was at least initial buy-in from leadership since it was the
leadership that arranged for each tree-climbing training pro-
gram. But we suspect that climbing may have been discontin-
ued post-training, at least in part, due to leadership not being
directly involved during the training. At Jejak Pulang, on
the other hand, leadership was, and continues to be directly
involved throughout.
All of the students in the 2016 courses and all of the
students in the February 2018 course were men. Many of
them were not the actual orangutan caregivers, but instead
staff with other responsibilities at the centers. Most orang-
utan caregivers are women, acting as surrogate mothers,
Figure 3. The orphaned orangutan, Tegar, following her tree climbing surrogate
mother, Aoliya, into the canopy. Photograph © Four Paws | Nanang Sujana.
Figure 4. Tegar, an orphaned orangutan, encouraged by caregivers, Yani and
Aoliya, to climb into the canopy. Photograph© Four Paws | Nanang Sujana.
Tree climbing to help orangutan orphans
5
and women in Borneo, for cultural reasons, are less encour-
aged to participate in the tree-climbing program. The suc-
cessful February-2018 training at Jejak Pulang of only male
students (including actual caregivers) was followed by the
October-2018 and April-2019 training at Jejak Pulang that
included female orangutan caregivers. We were able to suc-
cessfully engage the main caregivers, by working closely
with the leadership in demonstrating the usefulness and worth
of the methodology.
The October-2018 course successfully instructed caregiv-
ers in climbing trees to encourage orangutans to be arboreal,
but the Tree Monkey Project also constructed two platforms
high up in the trees at the forest school that could be reached
with ladders. This allowed caregivers to be up in the trees
without the need or expertise of tree climbing. This method
improved on the caregiver interacting on the ground with the
orangutan in that it led to the orangutans being higher up and
spending more time in the trees, even though it lacked the
maneuverability in the arboreal environment for optimum
interaction between the caregiver and orangutan.
Conclusions
An orphaned and rescued orangutan’s acquisition of
competence in arboreal living skills is obviously critical to
its survival post-release. We have successfully taught orang-
utan conservation center staff throughout Borneo a standard-
ized tree-climbing methodology for working with young
orangutans in one important aspect of their rehabilitation. To
enhance effectiveness, the training should be well coordi-
nated with the onsite leadership and decision-makers of the
center. The leadership must be inclined towards innovation
and capable of, and committed to, adapting their existing pro-
grams. The tree-climbing training program for the conserva-
tion staff has had some initial success in so far as caregiv-
ers have climbed trees at the forest school and been able to
encourage the orphaned orangutans towards arboreal activ-
ity. Time will tell if this will be signicant in increasing the
success rate in reintroduction as a result of what we believe
will enhance their skills in moving about in their arboreal
world. Next steps may be to carry out comparative studies
of the well-being and skills of those orangutans that receive
care that extends to providing this extra arboreal activity with
those that perchance do not, and to subsequently accrue data
on rehabilitation success and the benets of tree climbing to
the maintenance, rescue, and research activities of the rescue
centers.
Acknowledgments
We thank the Tree Monkey Project and its donors for
nancially supporting these expeditions to teach tree climbing
to orangutan conservation staff, and the volunteers and lead-
ers of Tree Monkey Project, specically Jim Cairnes, Wouter
Baa, and Tamela Fish. We also thank all of the conservation
centers and staff that we trained throughout Borneo. Speci-
cally, we acknowledge the Matang Wildlife Center and the
leadership of Leo Biddle, Natasha Beckerson, and Dominic
Kelundek for supporting and coordinating the multiple train-
ings on the 2016 expedition, and we are grateful to Jejak
Pulang and Four Paws International and the leadership of
Signe Preuschoft for continued support and their partnership
in the 2018 and 2019 expeditions.
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Authors' addresses:
Judah M. Epstein, Department of Math and Science,
Brookhaven College, 3939 Valley View Lane, Farmers
Branch, TX 75244, USA; and James Reed, Tree Monkey
Project, 2100 4th St., San Rafael, CA 94901, USA. E-mail of
rst author: <jepstein@dcccd.edu>.
Received for publication: 6 May 2019
Revised: 8 June 2019
