Experts at the National Aquarium in Baltimore believe two of their three female bottlenose dolphins are pregnant and due to deliver next February or March.
Successive blood tests during the past six weeks have revealed high hormone levels that indicate pregnancy, said Doug Messinger, curator of marine mammals.
"We still want to do one final diagnosis with ultrasound to try to locate the fetus' heart," he said. "In that way we would definitely [know we] have pregnant animals. But we're pretty confident that we do."
If successful, the pregnancies would be a high-water mark for the aquarium, which had barely opened in 1981 when Gretel, one of its first dolphins, died of a bleeding ulcer attributed to stress and pre-existing illness. Three other dolphins showed similar symptoms and were returned to Florida.
Studies found that poor design of the aquarium's main display XTC tank contributed to the animals' high stress levels, and extensive alterations were ordered. But a second dolphin, Duffy, died of infections in 1984 while on loan to the aquarium.
Duffy's death was blamed on a pre-existing condition, but the aquarium did not attempt to display bottlenose dolphins again until the completion of its new $35 million Marine Mammal Pavilion, which opened last Dec. 26 boasting a far larger, quieter and more carefully designed display area.
The animals began "extensive and almost disruptive" breeding in February, Messinger said. "I don't think we could have hoped for more after having these animals here less than a year. We can definitely count our blessings."
He attributed the quick results of the aquarium's breeding program to a good "social group" of animals and good nutrition. An average of 19 dolphins are born in captivity each year in the United States.
The Baltimore dolphins believed to be pregnant are Shiloh and Hailey, both 11-year-old, 300-pound females captured in 1981. They were acquired by the aquarium last October from a Florida Keys firm and flown to Baltimore Oct. 23.
They joined three older dolphins -- two males and a female -- collected from the Gulf of Mexico in 1975 and 1977 by a Galveston, Texas, marine park. Those dolphins were acquired by the aquarium and brought to Baltimore last August.