Weighing our animals regularly is important because it’s a good tool for monitoring their health and their diet. A sudden weight loss (or gain) can indicate the animal may have a problem.
Some animals, like our orangutans, can be a real challenge to weigh because they are incredibly strong and naturally curious. Finding a way to use a scale without them being able to get their hands on it (and thus destroy it!) took some creative thinking on our part. We decided the best method would be to use a hanging scale above their enclosure and out of reach. We recycled a thick PVC sleeve large enough to hang a scale inside of it, and strong enough to hold several hundred pounds. The PVC tower would be bolted permanently to the top of the enclosure and the scale would be hung on a bolt inside the tower for weighing. The mesh on top of the enclosure prevents the orangutans from getting a good grip on the scale.
Now, how do we get them to hold onto the scale? It was decided the best chance of success is to reward while they sit still on the platform. How? Here’s what we came up with: An ordinary plastic cutting board bolted directly to the floor of the platform. Numerous divots were cut into the face of the board, allowing us to add maple syrup or honey as a treat. The divots make it harder to get to the reward, thus helping to get an accurate scale reading.
On weighing day, the scale is placed in the tower, the platform attached with a lock, and the cutting board smeared with honey. A keeper is stationed on top of the enclosure to read the scale. The orangutans were let in the room one at a time. The picture to the right is of Dara, who after a minute or two let go of the mesh with her right leg and sat completely still. She weighed in at 125 pounds, right where a female orangutan her age should be. With a fairly reliable weighing method, our goal is monthly weigh-ins. It’s been a lesson in improvising and ingenuity and it’s results like this that help make our jobs so rewarding.
– Brian Sheets, zoo keeper