Everybody thought the sloths were just friends. So Baby Sloth shocked the Colorado zoo

Bosco and Chalupa appeared to just be sloth friends.

The male and female sloths lived together for four years and they never, ever showed any signs of breeding, according to a statement from the Cheyenne Mountain Zoo in Colorado.

That’s why it was “quite a surprise” when zoo staff noticed Chalupa was pregnant during an “unrelated” veterinary visit, the release says.

“Sloths are famously adored for their slow-motion lifestyles,” animal care manager Joanna Husby said in the statement. “Even successful breeding and conception can take longer for sloth parents than other animals.”

Because sloths are nocturnal, zookeepers think the Hoffman’s two-toed sloths may have mated after zoo hours, according to the news release.

“This baby was worth the wait, though,” Husby said. “It’s pretty cute, with dark fur, really dark eyes and the most adorable little nose.”

The baby sloth was born at 12:15 p.m. on May 14.

“The baby appears to be strong, and first-time mom, 19-year-old Chalupa, is exhibiting quality maternal instincts,” the release says.

The zoo posted a video to Facebook, which shows Chalupa and her “little bundle of joy” cuddled up in a hammock-like net.

Zookeepers will not know the baby sloth’s gender for “months,” the release says, and there are no plans to name the baby yet.

“Chalupa and her baby are visible to guests in Monkey Pavilion, but will be in an exhibit with a little more privacy for at least a few months,” the zoo said. “Bosco, the baby’s 27-year-old father, will remain in the sloths’ normal exhibit, hanging out above the guests’ pathways inside and outside of Monkey Pavilion.”

The mom and her baby will return to their normal exhibit when it is determined safe to do so, the zoo said.

“Chalupa and the baby are bonding well, and we’re excited to watch this little sloth grow up,” Husby said.

This isn’t the first time a zoo baby has surprised zookeepers.

Earlier this year, in North Carolina, a lemur’s birth control failed and she became pregnant, McClatchy reported.

“Mom Gertrude was on birth control so she wouldn’t conceive early on in her relationship with lemur Remus, the Duke Lemur Center announced...,” according to McClatchy. “It turns out contraceptives for lemurs aren’t always effective.”

Related stories from Sacramento Bee