The beluga population in Cook Inlet is not bouncing back and scientists are trying to figure out why.
First, they need to know more about the population. A key part of that is knowing how old the whales are.
“Up until this point, the only way we’ve been able to age animals is through their teeth," said Verena Gill, a branch chief with NOAA Fisheries.
“You count the rings in your teeth, kind of like you count tree rings," she said. "We can’t exactly go run around the inlet, jump on top of beluga, yank one of its teeth out and count the rings on the living animal and go, ‘OK, well, Betty Beluga out there is 10.’ So the only way we’ve been able to get teeth are from animals that have died.”
But now, researchers have found a way to determine the ages of living Cook Inlet belugas using skin samples. That technique is outlined in a paper published last month by researchers from NOAA Fisheries, Oregon State University and University of California Los Angeles.
It’s a big deal for researchers who study these whales. NOAA lists Cook Inlet belugas as one of its nine “Species in the Spotlight,” meaning they’re at high risk for extinction.
The technique relies on epigenetics. While genetics concerns DNA, epigenetics is about how that DNA is modified.
“So the term itself is a little bit of a catchall, because it actually includes a lot of different processes," said Ellie Bors, a postdoctoral researcher on the study. "But I like to think of epigenetics as all these other ways that DNA is modified or packaged within a cell that affects the way DNA turns into genes and proteins."
In particular, researchers looked at a specific epigenetic process called “DNA methylation.” That means organic compounds, called “methyl groups,” are being added to DNA.
“And it turns out that as a lot of mammals age, the way that DNA is methylated changes, or the amount of methylation changes with age," Bors said.
Scientists can tell how old a beluga is based on how its DNA is methylated. And they can get that DNA through tiny skin samples of living whales.
Other species, like humpbacks, have patterns on their bodies that indicate age. Not belugas.
Paul Wade works for NOAA Fisheries’ Alaska Fisheries Science Center and was a co-author of the paper.
“Being able to estimate the age of a living animal just can be so important for us," he said. "I’ve always been jealous of colleagues that study different species where they can know the age of their animals just ’cause they know so much about their population.”
He said this technique will help with a lot of research in the works about Cook Inlet belugas.
A lab in San Diego is studying pregnancy rates in belugas using hormones found in their blubber. Researchers knew what percentage of these whales were getting pregnant but they couldn't tell the age of the pregnant whales.
“But as soon as we got the ages and plotted pregnancy or not versus age, we noticed that it was only the older whales in our study that showed a fairly high pregnancy rate," he said.
It was a small sample size, Wade said. But when scientists compare those findings with that of healthy beluga populations, they show reproduction among Cook Inlet belugas could be delayed. That might be a sign the population is struggling due to external factors, like a lack of food.
Findings are preliminary. But Wade said scientists feel they’re getting closer to knowing why Cook Inlet belugas aren’t rebounding.
Kenai Peninsula residents who are excited about beluga research can participate in local efforts, like the Cook Inlet Belugas Count, a one-day event that uses volunteers in Homer and Kenai to count whales.
There’s also the Alaska Beluga Monitoring Partnership, a program that takes place in the spring and involves training. Visit akbmp.org for more information.