A bonnethead shark pup made her debut at Shedd Aquarium in mid-January. The first-time mother and pup have been attentively cared for and are doing great. When aquarists suspected the female was pregnant, they worked with the Animal Health team to orchestrate an exam and the female’s move from the Caribbean Reef habitat to a private pool behind the scenes.
A beautiful shark
After observing mating behavior about eight months earlier, aquarists were fairly certain one of the female bonnethead sharks in the Caribbean Reef was pregnant. To give the shark the best care possible, members of the Fishes and Animal Health departments scheduled an ultrasound exam during Shedd’s two-day maintenance shutdown in January. With the building empty of guests, they could set up their portable equipment next to the Caribbean Reef.
Peering into the 90,000-gallon exhibit, Dr. Caryn Poll, senior staff veterinarian, studied her patient while pointing out the visible contrast between a slender male bonnethead and the full-bodied female. As the pregnant fish glided close to the glass, the veterinarian noted, “She’s a beautiful shark. Her skin and fins look great.”
Other members of the medical team were busy adding a fish anesthetic to a water-filled exam transport, setting up the ultrasound monitor and arranging airlines from an oxygen tank into the water to provide the fish with dissolved oxygen to breathe. Because bonnetheads are obligate ram ventilators—they have to swim to breathe—and the fish would be still during the exam, senior aquarist Eve Barrs and another team member were ready to gently direct aerated water through the shark’s gills.
Meanwhile, an expert scuba ensemble consisting of two senior Fishes department staffers and two longtime volunteer divers talked through the plan to move the shark, finetuning it step by step.
At the top of the Caribbean Reef, diver Michelle Sattler took up her position alongside a large floating kiddie pool filled with habitat water to which a veterinarian had added anesthetic. At 11:12 a.m., the other three divers slipped into the exhibit.
Communicating by hand signal, the dive team took less than a minute to encompass the female with soft nets designed especially for sharks and gently swim her into the kiddie pool. The anesthetic quickly took effect, and the fish was whisked to the waiting transport. It was 11:16.
While a gentle flow of water was directed across the stationary shark’s gills. Dr. Caryn took the heart rate, which she noted was good. Suddenly the pup squirmed in the shark’s abdomen. “It was like watching a baby kick,” said Eve, who was holding the mom in position for the ultrasound. Working quickly, Dr. Caryn moved the scanner over the shark’s belly, visually confirming the presence of a pup.
Clad in elbow-length neoprene sleeves—repurposed arms from worn-out wetsuits—to protect the skin of both the bonnethead and her human handlers, Eve and another aquarist gently transferred the fish into a second transport containing a lighter concentration of sedative to start the recovery process. The shark rested in a protective sling to keep her from bumping her shovel-shaped rostrum or scuffing her skin. At 11:20, a group of veterinarians and aquarists rolled the fish into an elevator to a lower level.
Thirteen minutes after the procedure began, the shark was back in regular saltwater. Michelle, in scuba gear, floated in the center of the kiddie pool, slowly pirouetting as she guided the shark around the padded perimeter to help her ventilate as she recovered.
At 11:40, Dr. Caryn observed, “She’s swimming consistently on her own now and picking up speed.” With the go-ahead from the Animal Health team, Michelle leaned on one side of the pool to let the shark glide out, then followed her as the fish moved into the whole space. In response to a radioed inquiry from elsewhere in the aquarium, an aquarist reported, “She’s doing well.”
“At the 2 o’clock check, I saw two sharks.”Eve Barrs, Aquarist
The bonnethead was monitored nonstop for two hours. Then, Eve said, “Because everything had been consistent, we made half-hour checks.” At 1:30, nothing had changed. “At the 2 o’clock check,” Eve continued, “I saw two sharks.
“From its wiggly movement, the pup looked like it had just been born,” she said. “The fins and bonnet were slightly curled from being inside mom, but it looked healthy.” As a newborn shark pup swims, the motion lets its cartilage fan out, straighten and firm up.
Independent from birth
A shark pup can fend for itself from the start. “The little bonnethead came out ready to eat,” Eve said. “She was tracking food, smelling the shrimp and krill we put in there, which was a great sign.” As she’s grown, her diet has expanded to include blue crab and small fish called silversides, which she either takes from tongs or forages off the bottom. The pup was moved to her own enclosure, where she is being monitored during the critical first months. The team caring for her reports that she is “eating like a champ.”
Mom shark will also continue to stay behind the scenes for a while. “Our goal is for her to put some weight back on,” said Eve. That includes building up her fatty liver. “It’s normal for sharks to have a large liver,” Eve explained. “It’s critical to their buoyancy.” But during pregnancy, as the female is using extra energy to produce a pup, her body taps into her liver’s metabolic resources.
“We want to make sure she has plenty of time to regain liver size, put on weight and be robust again,” Eve said. “She gave us a healthy, adorable pup. She deserves to have her own room for a while.”
“She gave us a healthy, adorable pup. She deserves to have her own room for a while.”Eve Barrs, Aquarist
The birth marks the first second-generation bonnethead born at Shedd. The mother was born at another Association of Zoos and Aquariums-accredited facility and came to Shedd in 2017. It’s a significant milestone for us in supporting a self-sustaining population of this small, fascinating hammerhead species.