A chimpanzee at a Louisiana animal sanctuary has given birth to a baby, despite all of the males living with her having had vasectomies.
Staff realised something was up when they could not spot Teresa
Workers at Chimp Haven in Keithville were amazed to find the mother, Teresa, cradling a baby as she walked through the wooded compound on 8 January.
Both Teresa and her daughter, named Tracy, are said to be doing well.
Staff say vasectomies are not always successful and paternity tests are now under way to see who is the father.
Chimp Haven is a 200-acre (81-hectare) retirement facility for chimpanzees who have previously been used in laboratory experiments.
Workers at the sanctuary first realised something was awry when Teresa, who is in her 40s and was born in the wild, was missing during morning checks.
Much to their astonishment she appeared later in the day carrying a baby.
"Well, we were all just a little bit surprised when we heard the news," Linda Brent, a spokeswoman for Chimp Haven, said.
The baby is reported to be strong, alert and nursing regularly.
According to Amy Fultz, a chimpanzee behaviour expert at Chimp Haven, Teresa is very protective of her young charge.
"Teresa has been holding the baby tight in her arms and allowing the other members of the group to take quick peeks at the baby," Ms Fultz said.
"She is spending most of the day out in the woods with her, and seems to like to rest in the sun with the baby. On her second day of life, Teresa had the infant with her while she was high in the trees eating."
The 19 other chimpanzees in the group have taken on similar custodial roles, with Teresa's closest female companions each taking on the role of "aunt", Ms Fultz said.
"This group of females is protective of both Teresa and the baby, and they are always alert when she is nearby," Ms Fultz said.
A local man has volunteered to pay for Tracy's lifetime of care
Tracy is Teresa's 11th baby, though her first for 13 years and the first born at the sanctuary.
Managers say that all seven of the male residents received vasectomies before arriving at the park, but one at least was clearly not successful.
"This really shows that no matter what precautions you take, life finds a way," Ms Brent said.
Now hair samples are being taken from the males in order to establish who is the father, and get him back into the operating theatre as soon as possible.
As for baby Tracy, her future is looking rosy. A local donor to the haven, William Robinson, has offered to cover the cost of her care at Chimp Haven for the rest of Tracy's life.
"Tracy is one of the few chimpanzees born into an environment where she will be able to learn natural behaviours such as foraging, climbing trees and nesting from a group of wild-born chimpanzees," Ms Brent said.
"This is a rare opportunity for Teresa to teach Tracy the skills she learned from her own mother in Africa so long ago."