A fourth beluga whale rescued from a troubled Canadian marine park has died, marking the third death among the group at Chicago’s Shedd Aquarium following their transfer this summer for rehabilitation. Additionally, a longtime beluga resident of the Shedd has recently passed away.

The latest to die was Osiris, a 26-year-old female beluga, who had faced ongoing health challenges. She was among the first four rescued whales brought to the Shedd in mid-July. Aquarium staff observed changes in her behavior and respiratory function on Monday morning, leading to a rapid decline despite intensive care efforts. The cause of Osiris’ death remains unknown pending a necropsy.

Earlier this month, two other rescued belugas died at the Shedd: 20-year-old female Rain and 23-year-old male Peekachu. Another beluga, Beethoven, a 34-year-old male who had been at the Shedd since 2014, also died recently. Separately, Jelly Bean, a beluga that had been transferred from Canada to Oceanogràfic Valencia in Spain, died last Friday.

All of the whales originated from Marineland, a marine park in Niagara Falls, Ontario, that recently closed. The whales were evacuated amid reports that Marineland caretakers threatened to euthanize them. More than 30 whales were removed from the facility, with 10 arriving at the Shedd in multiple groups over the summer and early September, effectively doubling the size of the aquarium’s beluga pod.

According to the Shedd Aquarium, each rescued beluga arrived with unique life histories and health conditions that posed significant challenges to their rehabilitation. Osiris, in particular, struggled with maintaining a consistent appetite. While she initially responded to fluids, medication, and care, and even showed signs of engagement with other whales, her health ultimately deteriorated.

The aquarium emphasized that nutrition was only one aspect of overall health and noted that recovery in complex cases is often nonlinear. The institution expressed gratitude to those following the rescue and reaffirmed its commitment to transparency and scientific investigation into the causes of the whales’ deaths.

Results from necropsies and further analyses on the earlier deaths remain pending. The Shedd acknowledged the inherent uncertainties involved with caring for animals with preexisting vulnerabilities and reiterated that the outcomes for each whale could not be assured from the outset.