They describe the baby Goeldi's monkey as "extraordinarily small."
A typical Goeldi's monkey weighs around 50 grams -- or 1.8 ounces -- at birth. This baby girl weighed just over 34 grams -- or 1.2 ounces -- when primate keepers found her clinging to a branch in the Goeldi's monkey house.
Her mother Kylie didn't show interest in the newborn so the animal care team is hand-raising her. To encourage parental bonding, they moved Kylie and father Opie into the animal hospital where Betty is being treated.
Photos: Tiny monkey born at Houston Zoo
They will keep them there for the next few months until Betty is big enough to survive on her own.
The smallest Goeldi known to have survived was 42 grams, according to the Association of Zoos and Aquariums. The Houston Zoo team said they're "cautiously optimistic" about Betty's chances.
This isn't the first time the Houston Zoo’s animal care team has hand-raised primates.
Over the summer, they spent months raising a ring-tailed lemur named Cleo who was also smaller than average. They say Cleo has come a long way and rejoined her troop.
In 2020, the team hand-raised a Schmidt's red-tailed monkey named Peter Rabbit.
In the wild, Goeldi's monkeys typically live in groups of two-12 in the trees of the Amazon rainforest. They weigh only around a pound when they're fully grown.
A female Goeldi’s monkey is pregnant for about five months and normally gives birth to a single baby. She typically carries the infant on her back for a few weeks before she lets dad near it.
Goeldi's that are too small to grip onto their parents' fur usually don't survive unless they're hand-raised, according to the Houston Zoo.