This summer the Brookfield Zoo’s bottlenose dolphin habitat will reverberate with the chatty whistles and playful leaps of a new calf — the first expected to be born there in over a decade. On Wednesday, the zoo announced the upcoming addition to its seven dolphins as 37-year-old Allie enters her second trimester of pregnancy.

Almost 20% of dolphin calves born to first-time mothers in the wild don’t survive their first year. It’s a crucial time full of challenging milestones, so Allie — already an experienced mother of four — and her new calf will offer the zoo’s staff a chance to deepen its knowledge and contribute to the scientific understanding of prenatal and neonatal dolphin care.

“Our dolphins here at the zoo serve an incredibly important role in inspiring people and connecting them to wildlife and nature,” said Mike Adkesson, the zoo’s president and CEO. “We’re tremendously excited to be back in a position where we will be welcoming a new little one shortly.”

Brookfield Zoo has a long history of dolphin care and research. In 1961, it opened the country’s first inland dolphin aquarium. For over five decades, the zoo has also led the Sarasota Dolphin Research Program in Florida, the world’s longest-running wild dolphin conservation program, which studies bottlenose dolphins as indicators of the overall health of the marine ecosystem, as well as the presence of diseases and toxins like contaminants, runoff, red tides and algal blooms.

Bottlenose dolphins are one of the more common dolphin species in the wild — the kind humans might encounter while boating — and do well with humans in settings like zoos where they become bonded with the staff.

In both environments, they equip scientists with knowledge and experience that allows them to study and care for more endangered species as nearly one-third of marine mammals face extinction. For instance, the Sarasota team is involved in work with Franciscana or La Plata river dolphins in Argentina, which are classified as vulnerable by the International Union for Conservation of Nature.

Brookfield’s bottlenose dolphins returned home in early 2024 after being housed at the Minnesota Zoo in Apple Valley, Minnesota, for more than a year. During that time, their Seven Seas habitat was undergoing a $10 million renovation based in part on a Cetacean Welfare Study led by the Brookfield Zoo involving 86 dolphins across multiple facilities.

The renovation added some dynamic elements to the habitat to enrich the dolphins’ daily lives and encourage natural behaviors. These included a shallow sand pit to hide toys and food in, as well as new rock structures with built-in bubbler systems for the dolphins to play and with anchors to which staff can attach kelp and floating objects.

Their return allowed the zoo to resume its dolphin breeding program after the last birth in 2014.

Dolphin pregnancies last 12 months and are divided into four-month trimesters. Allie has been participating in medical checkups with veterinary staff, including ultrasounds and blood work. Changes in behavior indicating imminent labor might show up as early as May, so the animal care staff has been keeping a close eye on her.

“She’s been the model of a perfect pregnancy. We feel very good with how she’s been doing so far,” Adkesson said. “She’s active, she’s happy, she’s energetic, and, by all means, the calf is developing normally. The ultrasounds look great. All the blood work has been fine.”

Once she’s ready, Allie will have a water birth — which is normal for dolphins. As is also standard for marine mammals, her calf will come out tail first to reduce the risk of drowning.

“Because as soon as they come out, their mom has got to get them up to the surface of the water so that they can take those first breaths,” Adkesson said. “By coming out tail first, it allows that delivery to be a little bit smoother for calf and mom both.”

After delivery, the dolphin habitat at the zoo will be closed for the newcomer’s first days or weeks and reopen to the public depending on the calf’s progress.

He emphasized the dolphins’ role in inspiring a connection to the ocean and all waterways, beginning with drains in the city to local rivers, the Mississippi River basin and, ultimately, the Gulf of Mexico.

“For so many people, we are the only chance that they have to see a dolphin. They’re not going to make it out into the ocean and go scuba diving and have the opportunity to interact with these animals. Even when you do get out and scuba dive, you’re not necessarily seeing a dolphin for a long period of time,” Adkesson said. “And the heart of our experience here at the zoo is connecting people to that wildlife, so they have the chance to learn, to care about it and to want to conserve it.”

Visitors at the Brookfield Zoo can identify Allie in the Seven Seas habitat by her distinctive features, including faint white lines along the sides of her head and chest, pink coloration on the underside of her slender and long snout-like mouth and the gray underside of her body.

Located at 8400 31st St. in Brookfield, the zoo is open daily from 10 a.m. to 5 p.m. Admission is free on Saturdays, Sundays, Tuesdays and Thursdays through Feb. 27 and this Monday for Martin Luther King Jr. Day. For more information, go to brookfieldzoo.org/visit or call 708-688-8000.

adperez@chicagotribune.com