The zoo's veterinary team uses scans to monitor animal health.
In the spooky spirit for Halloween, the zoo shared skeletal snapshots of some of the zoo's wildest residents.
Puerto Rican crested toad
Native only to Puerto Rico, the zoo says the Puerto Rican crested toad is a rare amphibian. Adding that the head has a distinctive bony "crest" above the eyes.
Tamandua
The zoo said instead of teeth, the tamandua anteaters use long, sticky tongues coated in thick saliva to catch insects.
Toco toucan
Famous for its oversized bills, the toco toucan's beak can reach up to eight inches, about one-third of its body length, according to Brookfield Zoo Chicago.
Gibbon
Gibbon apes are acrobats of the canopy, swinging from branch to branch with arms that can stretch up to 5 feet, the zoo said.
Asian small-clawed otter
The Asian small-clawed otter is the smallest otter species in the world, the zoo said. It weighs just 4 to 11 pounds and is about 16 to 24 inches long.
Leopard tortoise
The leopard tortoise is the fourth-largest species. The zoo said its tall shell has steep sides, giving it a dome look.