New method helping scientists gauge age of Southern Resident killer whales

Scientists are using skin samples from endangered southern dwellers and other whales in what is being touted as a promising new way to estimate the age of mammals.

Knowing the life history of individual animals and how their populations have changed over time is important, but it’s difficult to accurately estimate the age of wildlife — especially long-lived animals like whales — according to the National Oceanic and Atmospheric Administration (NOAA).

Researchers at NOAA’s Northwest Fisheries Science Center and other scientists used a new technique to determine the age of the whales, and their results were published in late March in the scientific journal Resources for Molecular Ecology.

Whale age studies rely on epigenetics, which explores how DNA is modified, or packaged, inside cells. The researchers studied a modification called methylation, which turns genes on and off and is able to assign an “epigenetic clock” to individual whales. These estimates are expected to be within three years of the actual age of the whales.

“Accurate estimates of the age of individual whales are important for understanding the health of individuals and trends in killer whale populations,” EPA said.

The researchers examined skin cell samples from southern and Alaskan resident killer whales, as well as Beagle killer whales. It also includes Fisheries and Oceans Canada, which allows Canada’s Aboriginal hunters to collect samples from bowhead whales, one of the longest-lived mammals on Earth.

With the epigenetic approach, scientists only need small skin biopsy samples taken from living animals using minimally invasive techniques. According to the study, an epigenetic clock can be assigned due to the strong correlation between methylation patterns and age recorded in both humans and non-human vertebrates.

The study also used samples of whales that had died in the past, and drew on data on southern dwellers that had been collected over the past few decades, as there are many well-documented individuals belonging to closely watched species.

“While we know a lot about the age structure of southern residents, we don’t know the age of individual whales,” NOAA said. “Most killer whale populations are far less well studied than those in the Pacific. The epigenetic clock could help fill these gaps.”

The epigenetic approach to aging is not perfect, but as NOAA points out, cells in other mammals, like humans, can age faster or slower depending on environmental variables such as diet, lifestyle and stress.

Still, NOAA says the strategy holds promise for helping scientists monitor patterns of age-related disease and detect changes in survival and birth rates in whale populations. The agency said it is also currently examining epigenetic data from populations of killer whales around the world.

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