One by one, they hop on and hop off the scale set by Aquarium biologist Chevonne Jackson. It’s marmoset weighing time.

Chevonne weighs the Goeldi’s marmosets (Callimico goeldii) once a month for health reasons. “We closely monitor their weight, which is usually a good indicator of health,” she says.

While it looks like the marmosets know exactly what to do, there was a long period of training beforehand to desensitize them to the equipment. As Chevonne says: “Goeldi’s tend to be skittish animals. They’re normally wary of new things and take a while before they’ll come close to new objects.” To keep things familiar, Chevonne places a heavy rock-like dish, which the marmosets previously learned to associate with food, on top of the scale.

Chevonne does a visual check of the Goeldi's marmoset's body at the same time as weighing.

Chevonne does a visual check of the Goeldi’s marmoset’s body at the same time as weighing.

Chevonne positively reinforces the marmosets for their efforts with food, such as mealworms and raisins. A small target stick tells them where to go and helps them stay focused.

This Goeldi's marmoset sits in a rock-like dish on top of the scale.

This Goeldi’s marmoset sits in a rock-like dish on top of the scale.

Goeldi’s marmosets use their tails to balance, but this can be a problem if they rest their tails on branches or the ground because it could result in inaccurate readings. So Chevonne places the scale on a stool and makes sure their tails are not touching anything, while a second Aquarium biologist records several readings to get the most accurate weight.

Chevonne worked as a zookeeper for seven years in Ontario before coming to Vancouver Aquarium Marine Science Centre. Her previous experience is with big cats and other large mammals. Now, she’s working with some of the Aquarium’s smallest mammals at 400 to 700 grams.

Need more marmoset in your life? Watch this hypnotizing video of one licking a melon at the Aquarium.

Written by Karen Glanzberg, writer-editor, content and digital experience at the Vancouver Aquarium Marine Science Centre.

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