What's Killing Killer Whales?

Not only do PCBs stick around, they build up in animals’ bodies. They bind to fat, which is abundant in marine mammals as blubber. The chemicals cling to fat in the milk of mother whales too, passing from mom to baby. And PCBs become more concentrated as larger animals eat smaller ones. As predators at the top of their food web, orcas have the highest measured PCB levels of any animal (see Trouble at the Top).

Desforges and a team of scientists set out to analyze the amount of PCBs in more than 350 orcas across 19 whale populations worldwide. The data came mainly from blubber samples previously collected for other research. Desforges’s team made a computer simulation that predicted how those PCB levels will affect the populations in years to come.

PCBs don’t just stick around. They also build up in animals’ bodies. They bind to fat, and marine mammals have a lot of fat, called blubber. The chemicals stick to fat in mother whales’ milk, too, and they get passed from mom to baby. When larger animals eat smaller ones, they take in more PCBs. Orcas are predators at the top of their food web. They have the highest measured PCB levels of any animal (see Trouble at the Top).

Desforges and a team of scientists looked at the PCB levels in more than 350 orcas. These whales lived in 19 populations around the world. Scientists had already collected blubber samples for other studies. That’s where most of Desforges’s data came from. His team used a computer model. It predicted how those PCB levels may affect the whale populations in the future.

PCB exposure takes a toll on killer whales’ health. The chemicals can cause cancer and limit orcas’ ability to fight off illnesses. PCBs also make it difficult for females to have healthy babies. No southern resident calf, for example, has survived since 2015.

Desforges’s simulations showed that 10 of the 19 studied populations will experience a significant downturn within the next century. Half of the groups may not survive. “We knew [PCB] concentrations in killer whales were really high, but it was surprising to see how many populations were seriously affected,” says Desforges.

PCBs hurt killer whales’ health. The chemicals can cause cancer. The orcas have a harder time fighting off illnesses. And PCBs make it difficult for females to have healthy babies. For example, no southern resident calf has survived since 2015.

Desforges’s computer model showed bad news. Ten of the 19 populations will undergo a big decrease in the next century. Half of the groups may not survive. “We knew [PCB] concentrations in killer whales were really high, but it was surprising to see how many populations were seriously affected,” says Desforges.

Biologist Lynne Barre leads the National Oceanographic and Atmospheric Administration’s (NOAA) marine mammal conservation efforts in Seattle. She attended the hearings and understood the outpouring of emotion. “People feel connected to killer whales,” says Barre. “They live in family groups, they’re intelligent, and they care for their young. People relate to that.”

At the meeting, some people were upset NOAA hadn’t tried to treat a sick juvenile southern resident whale called J-50 before she died. NOAA had helped other orcas in the past, like a calf named Springer who became separated from her mother. Barre and other scientists cared for the calf until she was healthy enough to rejoin her family. Unlike Springer, though, J-50 was still with her mother. NOAA experts decided it was best for them to stay together and hope J-50 pulled through.

Lynne Barre is a biologist with the National Oceanographic and Atmospheric Administration (NOAA). She leads their marine mammal conservation efforts in Seattle. She went to the hearings and understood how the people felt. “People feel connected to killer whales,” says Barre. “They live in family groups, they’re intelligent, and they care for their young. People relate to that.”

At the meeting, some people were upset. That’s because NOAA hadn’t tried to treat a sick juvenile southern resident whale called J-50. The calf died. NOAA had helped other orcas before. For example, they’d helped a calf named Springer who got separated from her mother. Barre and other scientists cared for the calf. When she was healthy enough, she returned to her family. But J-50 was still with her mother. NOAA experts decided it was best to leave them together and hope J-50 pulled through.

Although people were saddened by the death of J-50, there is good news for the southern residents: Several are pregnant. “I’m hopeful we’ll see new calves in the coming months,” says Barre. Desforges notes another bright spot: Populations in remote areas where PCB levels are lower, including Norway and Antarctica, are growing.

Also, PCBs in the environment are decreasing as they gradually break down. But there are still a lot of old contaminated materials that could potentially find their way into the ocean. “We’re reducing PCBs, but we haven’t gone far enough to be certain they’re kept out of the environment,” says Desforges. “We have to do better.”

The death of J-50 saddened people, but there is good news for the southern residents. Several are pregnant. “I’m hopeful we’ll see new calves in the coming months,” says Barre. Desforges notes another bright spot. In remote areas like Norway and Antarctica, PCB levels are lower. There, whale populations are growing.

Also, PCBs in the environment are decreasing. Little by little, they’re breaking down. But a lot of old polluted materials are still out there. They could find their way into the ocean. “We’re reducing PCBs, but we haven’t gone far enough to be certain they’re kept out of the environment,” says Desforges. “We have to do better.”