Tess, an expecting 33-year-old Asian elephant at the Houston Zoo, miscarried two fetuses overnight, nearly halfway through her gestation.
The miscarriage revealed Tess was carrying two calves — an extremely rare instance of twins in Asian elephants.
Zoo officials made the announcement Tuesday "with a heavy heart."
Tess is now being watched closely for possible signs of physical and psychological effects from the miscarriage.
"Twins increase the chance of fetal loss in all species," Dr. Dennis Schmitt, a world-renowned elephant reproductive expert and Missouri State University professor, said in a statement. "In Asian elephants, twins may share a common blood course that can compromise the health of the calves.
"Twins can also present complications in delivery and compromise the health of the mother."
CultureMap reported in June that zoo officials had put Tess on a diet to shed 500 pounds to improve her odds of birthing what was thought at that time to be a single calf.
"As part of her prenatal care protocol, the elephant care team and zoo veterinarians monitored the progress of her pregnancy,” Dr. Joe Flanagan, Houston Zoo chief veterinarian, said in a statement. “Like all of our elephants, Tess was participating in an extensive wellness program."
Tess is now being watched closely by the entire elephant care team and the zoo’s veterinarians for indications of any possible signs of physical and psychological effects from the miscarriage.