ORLANDO, Fla. -- There's one last orca birth to come at SeaWorld, and it will probably be the last chance for research biologist Dawn Noren to study up close how female killer whales pass toxins to their calves through their milk.
While SeaWorld's decision last month to end its orca breeding program delighted animal rights activists, it disappointed many marine scientists, who say they will gradually lose vital opportunities to learn things that could help killer whales in the wild.
Noren got to observe only one mother-and-calf pair at a SeaWorld park before the end of the breeding program was announced.
"It's really difficult to publish with one. I really was hoping for a couple more, but that is what it is," said Noren, who works at the National Marine Fisheries Service's Northwest Fisheries Science Center in Seattle.
SeaWorld's 29 captive orcas in Orlando, San Diego and San Antonio could remain on display for decades to come and will be available in the meantime for study by outside scientists, as they generally have been for many years.
But as SeaWorld's orca population — with whales 1 to 51 years old — dwindles, researchers will lose chances to collect health data and make other observations, such as drawing blood, measuring their heart rates and lung capacity, and documenting their diets and their growth. As the animals age, scientists say, research will be limited to geriatric orcas.
No other marine park or aquarium in the world has SeaWorld's experience in maintaining or breeding orcas in captivity.
SeaWorld parks hold all but one of all the orcas in captivity in the U.S., and they have housed more than half of all captive killer whales in the world tracked by the National Oceanic and Atmospheric Administration over the past 50 years. Orcas held in Canada, Japan and Europe have not been as accessible to researchers.
SeaWorld will continue to support research projects underway on hearing, heart rates and blood, said Chris Dold, SeaWorld's chief zoological officer.
"There won't be an immediate crunch," he said. But he acknowledged: "Over time, yeah, there's a loss of this resource to society and science."
SeaWorld's critics, including People for the Ethical Treatment of Animals and WDC/Whale and Dolphin Conservation, sidestepped questions of whether outside researchers will suffer. But they said SeaWorld's own research has been unhelpful to orcas in the wild.
"SeaWorld has had the largest population of orcas and has had the opportunity to do useful research and had done none of that," said Jared Goodman, PETA's director of animal law.
Researchers outside SeaWorld argue they need its facilities and 1,500 employees in animal care to answer questions about wild orca behavior.
"If you want to interact with them and conduct research, the combination of talent you have to have is a scientist with a research question, animals that are healthy so that you're looking at normal physiological rates, and in between that are the trainers — and I think people miss that," said Terrie Williams, who runs the Center for Marine Mammal Research and Conservation at University of California, Santa Cruz.
SeaWorld's decision to end orca breeding and phase out its world-famous killer whale performances by 2019 followed years of protests and a drop in ticket sales at its parks.
The backlash intensified after the 2013 release of "Blackfish," a documentary that was critical of SeaWorld's orca care and focused on an animal that killed a trainer during a performance in Orlando in 2010.
In the wake of SeaWorld's announcement, some researchers fear that lawmakers on Capitol Hill and in states such as Washington and California will ban breeding or keeping of killer whales altogether.
Similar bans targeting other species would have stymied the captive breeding that revived the California condor, said Grey Stafford, incoming president of the International Marine Trainers' Association.
"Those bills can have unforeseen and unintended consequences if and when the next species has a population crash in the wild. It ties the hands of state agencies and sanctuaries and places like SeaWorld to act," Stafford said.
Kay contributed to this story from Miami.