Small VHF-Implants for Radio-Tracking Reintroduced, Free-Ranging Orangutans (Pongo pygmaeus)
American Association of Zoo Veterinarians Conference 2010

Chris Walzer1,, DECZM (Wildlife Health); Thierry Petit2,; Senthilvel Nathan3, DVM; Cecilia Boklin4, DVM; Symphorosa Sipangkui3, DVM; Gerhard Fluch1, DIng.; Benoit Goossens5, PhD; Marc Ancrenaz6,

1Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria; 2Zoo de La Palmyre, Les Mathes, France; 3Sabah Wildlife Department, Kota Kinabalu, Sabah, Malaysia; 4Sepilok Orangutan Rehabilitation Center, Sabah, Malaysia; 5Kinabatangan Wildlife Sanctuary, Danau Girang Field Centre, Sabah, Malaysia; 6Kinabatangan Orang-Utan Conservation Project, Hutan, Sabah, Malaysia

Read the Spanish translation: Uso de Implantes VFH Pequeños Para Radiotelemetría en Orangutanes Silvestres Reintroducidos (Pongo pygmaeus)


Numerous orangutan (Pongo pygmaeus) rehabilitation-reintroduction facilities exist throughout the species’ range. Today, some 1200 animals are held in Indonesia alone. The conservation value and impact of these institutions is controversial.2 With data lacking, an issue repeatedly and unsatisfactorily discussed is the success of reintroduction measures. In the past, radio telemetry has been viewed as unpractical and even dangerous in this species.1 In order to provide the numerous facilities throughout the orangutan range with a monitoring solution, we developed a small implantable VHF transmitter. The unit is controlled by a very low-power-timer-circuit that allows for a life span of several years. The preprogrammed VHF transmitting schedule (1–7 days/week and up to 24 hours/day) is activated in the field by the user. The electronic circuit is housed in a CNC engineered, inert ceramic casing, hermetically sealed with specially formulated epoxy glue. A magnetic interface is used to switch the unit into an ultra-low-power sleeping mode or start up the transmission schedule. The physical dimensions of the standard implants are 28 mm in diameter and 9 mm in height. To extend the theoretical lifetime of the transmitter a version with higher battery capacity is available which increases the height to 11 mm. The implants weigh 13 g for the standard size and 16 g for the extended size. To track the signal of the implants, a standard tracking receiver and adequate antenna covering the frequency range from 142–143 MHz should be used. Following initial trials in a zoo setting, the first implantations were undertaken at the Sepilok Orangutan Rehabilitation Center, Sabah, Malaysia. Units were surgically implanted in a subcutaneous pouch in the dorsal neck area. After placement, a standard 2-layer closure was performed. Initial field tests have demonstrated that these implants greatly facilitate the tracking of released orangutans in the field. With some 600+ and 50+ animals awaiting release in Indonesia and Malaysia respectively, these radio-telemetry implants will be a valuable tool in elucidating the fate of reintroduced orangutans.


The authors would like to thank Franz Schober and Perica Jurcevic for support in developing the implant and Signe Preuschoft, Anne Russon, Carel van Schaik for initial discussions. Partial funding for this initial study were provided by Hutan—Kinabatangan Orang-Utan Conservation Project and the Danau Girang Field Centre—Kinabatangan Wildlife Sanctuary.

Literature Cited

1.  Aveling, R.J. 1982. Orangutan conservation in Sumatra, by habitat protection and conservation education. In: L.E.M. de Boer (ed.) The Orangutan: Its Biology and Conservation. Dr. W. Junk Publishers, The Hague, The Netherlands. 299–315.

2.  Rijksen, H.D. 2001. The orangutan and the conservation battle in Indonesia. In: Beck, B.B., T.S. Stoinski, M. Hutchins, T.L. Maple, B. Norton, A. Rowan, E.F. Stevens and A. Arluke (eds.). Great Apes and Humans: The Ethics of Coexistence. Smithsonian Institution Press, Washington, DC. 57–70.


Speaker Information
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Chris Walzer, Dr., DECZM (Wildlife Health)
Research Institute of Wildlife Ecology
University of Veterinary Medicine
Vienna, Austria

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