About six months ago, in a humid pocket on the New England Aquarium's third floor, the anacondas were feeling tender. The two biggest snakes in Boston curled up together, probably in the watery pool of their
And so sometime in the next few weeks, for the first time ever in a Boston zoo or aquarium, a female anaconda will give birth, possibly to dozens of babies. Scientists at the aquarium have already seen images of some of the baby snakes, which are born live, during the mother's regular ultrasounds.
Anacondas, which come from the rain forests of the Amazon, give birth in American zoos or aquariums only once every few years. Breeding anacondas can be difficult because the snakes often don't feel relaxed enough in captivity to mate. And because of their size - anacondas are the heaviest snakes in the world, often weighing a few hundred pounds, and among the longest - many zoos have room for only a single snake.
Some keepers of anacondas try to set the mood for the snakes to breed, tinkering with their diet or environment. But while Scott Dowd, the aquarium biologist who oversees the anacondas, was hoping they would mate, he didn't concoct any special effects.
"It was more or less just a byproduct of them being happy," he said. "I think the snakes are just the happiest they've ever been."
For a while, Dowd and other scientists thought the aquarium's third snake, Kathleen (the two female snakes were named after longtime aquarium volunteers), might also be pregnant. An ultrasound this fall was inconclusive. But a few weeks ago, Kathleen released some eggs, some fertilized, some not. It was the first time she was known to have mated, Dowd said, and female anacondas have difficulty getting pregnant for the first time.
Meanwhile, ultrasounds of Ashley have left no doubt that she is pregnant. "We saw heartbeats," Dowd said. "It was really neat."
She has been removed from the main exhibition space and settled into a smaller area behind the scenes to prepare for the big day. Anacondas typically deliver between 20 and 60 babies, although the numbers can, in rare cases, exceed 100. "We could have a lot of baby anacondas," Dowd said.
Not long after the babies are born, Ashley will return to the exhibit. (Anaconda babies, which can swim and hunt within a few hours after birth, don't need care once they're born.) But the babies will spend some time in the smaller tank before they make their public debut in the large rain forest space, which is filled with plants and roots and pools of water.
"I worry I might lose track of some if she has them on exhibit," Dowd said.
Dowd has been talking to Bill Holmstrom, collection manager for the Bronx Zoo's department of herpetology and one of the country's most prominent anaconda experts, for advice. Holmstrom's anacondas last gave birth about two years ago.
Anacondas are born infrequently in the United States because snakes from the wild do not acclimate easily to life in captivity. "Just getting them to eat is difficult," Holmstrom said. "You need a lot of room. They live in the water almost all their life."
In the wild, he said, the chances of pregnancy are improved because female snakes often mate with more than one male.
To keep the anacondas calm, aquarium workers never forcibly restrain the snakes, even when they remove them from the exhibit. But they also take precautions: No one ever works with the snakes alone, or after handling food. Anacondas, members of the boa family of snakes, are carnivorous and kill their prey - typically rodents and small animals - by squeezing them to death.
Dowd grew up on the South Shore as a "pond kid," the youngest of six children. He was always fascinated by fish and began volunteering at the aquarium while still in high school. When he was offered a short-term job after graduation, he accepted - and was eventually hired permanently. Since he had his dream job, he never left for college.
But a few years ago, he went back to school, getting a master's degree in aquaculture from the highly regarded program at the University of Stirling in Scotland.
Dowd is convinced he knows the day that the baby snakes will arrive: Friday. Not because of any reptilian instincts, though - it's his wife's due date for their first child. When he learned that Ashley was pregnant, "I did the math in my head and thought, 'Oh, my God,' " he said.
But lest he feel conflicted about his loyalties should the births coincide, he said, "My wife has been clear about where my priorities are."
Kathleen Burge can be reached at kburge@globe.com.
