Even when given ample opportunities for climbing, it can be difficult to encourage captive orangutans to be as arboreal as they are in nature. In Denver, the orangutans enjoy a 16,633 square foot (~ 1/3 acre) outside yard with several mature trees, some reaching over 100 feet tall. Though they utilize the great climbing opportunities periodically, we were interested in encouraging them to climb more o�en. Pulley feeders have been discussed on ape list-servs at various times, but o�en are expensive and need to be custom fabricated in a metal shop. Denver Zoo has experimented with easy to obtain and affordable materials and has been continually evolving an easy to use, affordable arboreal feeder. Auckland Zoo, in New Zealand, has also had great success with home-made arboreal feeders. Three designs are presented here, each with its own set of challenges and benefits. Feeders like those used in Auckland are highly recommended, but if your zoo does not have the resources or political will to create something so permanent, don’t be discouraged – many other possibilities exist for creating arboreal feeding opportunities for orangutans.

DESIGNS1) Denver Zoo’s initial arboreal feeder, consisting of a rock climbing rope modified to have a stainless steel cable core, stainless steel cable pulley points and lacrosse balls to help keep the cable in place.

• Pros: Extremely affordable and easily replicable by unskilled cra�speople.

• Con: A�er extended use, the climbing rope bunched up around the cable, making it very difficult to raise and lower.

2) Denver Zoo’s current feeder, a simple rock climbing rope with lacrosse balls and eye-bolt pulley points. Eye bolts are 3/8” x 6” long, secured in the tree with wood glue & loctite.

• Pros: Very easy to install and use.

• Con: Not 100% orangutan proof.

3) Auckland Zoo’s design, utilizing stainless steel cables, pulley wheels, swivel connections, welded steel feeding basket and metal conduit.

• Pros: Relatively ape proof and durable over the long term.

• Con: Requires welding by skilled cra�speople and larger initial investment of time and funding, more effort needed to raise and lower.

ORANGUTAN PROOF?While in the planning phase, curators, keepers and vets in Denver agreed a design with minimal moving parts would be ideal. While the initial design worked wonderfully in the short-term and was reasonably “orangutan proof,” it created problems in the long-term: bare cables sawed through the pulley points and cables wrapped in rope eventually bunched up and made raising and lowering the feeder impossible.

Since a fully orangutan proof feeder (like those used at Auckland Zoo) may be mutually exclusive to one that is also affordable and simple to build and operate, we started taking the personalities of our individual animals into account. Only the first prototype of our arboreal feeder was “tested” in any way by the apes; subsequent models, even with clips and other pieces that could conceivably be removed by the orang-utans, were le� very much intact. With this in mind, and with the past history of the apes trad-ing unusual objects rather than using them to make trouble, curators and keepers felt comfort-able using a simpler system.

Michael Stern, Assistant Curator of Primates, Denver ZooCourtney Eparvier, Curator of Primates and Sea Lions, Audubon ZooAmy Robbins, Team Leader of Primates, Auckland ZooARBOREAL FEEDERS FOR ORANGUTANS

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Auckland Zoo's orangutan feeders (New Zealand)

Swivel mechanism at Auckland ZooOriginal Design, Denver Zoo, base of tree,

anchoring the cable

Original Design, Denver Zoo, cable pulley point

Current design, Denver Zoo, eye-bolt pulley point

Crank for raising & lowering the metal basket at Auckland Zoo