An Illinois aquarium has said that a third beluga whale it rescued from a closed marine park in Canada this summer has died after it struggled to acclimate to its new environment.

Osiris, a 26-year-old female, was one of 30 belugas removed from Ontario’s shuttered Marineland amusement park, and among 10 rehomed at the Shedd aquarium in Chicago, which said the whale died there on Monday.

Over the last month two other rescued belugas, named Peekachu and Rain, have died at the Shedd; and a 19-year-old male, Jelly Bean, one of two relocated to Oceanogràfic de València in Spain, died “suddenly and unexpectedly” last week.

“When Shedd was asked to help with this rescue, we understood that these animals arrived with significant vulnerabilities and that the outcome for every individual could not be guaranteed,” the aquarium said in a statement.

Beluga whales are particularly vulnerable to changes in their environment, such as climate change, pollution and other sources of stress, according to the National Oceanic and Atmospheric Administration (Noaa).

Native to Alaska’s Cook Inlet, belugas are classified as an endangered species, and their numbers have declined by almost 80% from 1979 to 2018.

The 30 whales, and a number of bottlenose dolphins, became the subject of what marine activists said was akin to a hostage situation following the 2024 closure to the public of Marineland, a troubled theme park on the southern shores of the Niagara river.

More than 20 whales and dolphins had died there since 2019, and a calamitous drop in visitor numbers and income forced the owners to abandon the venture. The Canadian government blocked the sale of the surviving animals to China, leaving them facing the threat of euthanasia.

A complex international operation moved 30 whales to aquariums in the US and Spain over the summer, but many did not take well to their new surroundings. The deaths were sudden and unexpected as their health wavered amid the challenges of adjusting to a new home, according to statements from the aquariums.

The rescued belugas were moved in custom-made slings and temperature-controlled containers, Shedd staff told the Associated Press. Aquarium personnel traveled to Marineland to examine their health records in preparation for the move. They have monitored their health minute by minute since they arrived, staff said.

Peekachu and Rain died at the Shedd in late August and early September after arriving from Canada. Another beluga, at the aquarium for decades, died around the same time.

Osiris was a “whale of clinical concern” since she arrived, according to the aquarium. The whale did not eat as consistently as her fellow animals, which complicated the efforts to keep her well-fed and hydrated, according to the statement.

“Osiris experienced periods of meaningful progress, both nutritionally and socially, but her overall condition remained closely monitored,” the aquarium stated.

Osiris’ caretakers noticed sudden changes in her behavior and breathing patterns the morning of her death, according to the aquarium. She was moved to the medical habitat, but “her condition declined rapidly,” and she “passed away despite lifesaving efforts”.

José Rafael Serra Díez, spokesperson for Oceanogràfic de València, said Jelly Bean’s death was also unexpected. The whale “experienced feeding difficulties, prompting the veterinary team to intensify her monitoring”, despite periods of improvement, the spokesperson said in an email to the AP.

The Georgia aquarium and SeaWorld locations in San Diego and San Antonio have also accepted whales from the Canadian park.

The two rescued whales at the Georgia aquarium showed decreased appetites and were examined, but no issues were found, the aquarium said in a social media post on Friday. The whales at SeaWorld are in “stable health”, according to AnneMarie Iturrizaga, a spokesperson for the company that owns the parks.

The Shedd aquarium notified Noaa of Osiris’s death Monday, according to John Chu, a spokesperson for Noaa Fisheries. Within 30 days of the whales’ deaths, the aquarium must formally submit their names and causes of death, and on request, provide copies of necropsy reports, Chu said.

The Shedd aquarium said it will conduct necropsies and share the confirmed results.

The Associated Press contributed to this report