Look who’s here! Black tree monitors hatch at Lincoln Park Zoo

Lincoln Park Zoo is celebrating a rare event: the birth of five black tree monitor lizards, marking the first offspring for a four-year-old female and her mate. The hatchlings, born between Oct. 27 and Nov. 2, are behind the scenes as they grow and adjust to their diets.

These new arrivals are part of the Black Tree Monitor Species Survival Plan (SSP), a collaboration between zoos and aquariums across the country to manage the species' population. With the addition of these five lizards, there are now approximately 70 black tree monitors at 29 accredited institutions nationwide. While the conservation status of the species remains unclear, experts are concerned that their populations are dwindling in the wild, largely due to overharvesting for the pet trade.

The black tree monitor's reproductive process is notably unique. Females bury their eggs in warm, elevated spaces, where they incubate for about 164 days. After hatching, the young monitors typically do not feed for several weeks, but the Lincoln Park Zoo hatchlings recently began eating insects, waxworms, and mice—an important milestone in their development.

Lincoln Park Zoo Curator Dan Boehm expressed excitement over the event, noting that this is the first time in 20 years that black tree monitor hatchlings have been born at the zoo. 

“Black tree monitors are limited to a relatively small geographic range in the wild, so maintaining a healthy population across AZA institutions allows us to learn even more about this special species,” Boehm said.

Black tree monitors, native to the Aru Islands off the coast of New Guinea, are easily recognizable by their slender bodies, long tails, and solid black color. Hatchlings, like the ones born at Lincoln Park Zoo, are dark gray with bright yellow-green dots. These solitary reptiles are arboreal, using their prehensile tails to balance and move through the trees.

While the hatchlings remain behind the scenes, the adult black tree monitors can be viewed by zoo visitors at the Regenstein Small Mammal-Reptile House.