Researchers off the coast of B.C. have uncovered a new method to determine a whale’s sex—DNA from seawater that whales have recently swam through.
The ongoing study, conducted by researchers with the global conservation organization Ocean Wise, was done over the last two winters around the Salish Sea. This research tracks the activity of four at-risk whale populations: southern resident killer whales, northern resident killer whales, humpback whales, and Bigg’s (transient) killer whales.
After collecting a seawater sample, scientists can isolate the whales’ environmental DNA (eDNA)—general material shed by organisms into their environment—and analyze it to determine species, individual identity, sex, and more.
“If we can ground truth some of these methods, they can be applied to other species at risk,” says Chloe Robinson, the director of the Ocean Wise Whales Initiative.
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Historically, determining the sex of wild whales was difficult, sometimes invasive, and costly. Scientists would observe whales with a calf, notice physical changes such as dorsal fin height at sexual maturity, take photos of the whale’s underside, or perform skin biopsies for DNA analysis.
In this study, researchers collected and compared the sex from southern resident killer whale eDNA samples against known sexes—determined from other identification methods—to see if this method could be used as a non-invasive alternative. Though the research is ongoing, Robinson says that 90 per cent of eDNA samples have matched the known sex of individuals.
“This is important for population persistence,” says Robinson, adding that southern resident killer whales have low numbers of males. Having access to this knowledge can help scientists figure out if there is a healthy enough balance of males and females to ensure the species survives.
These discoveries are part of a larger study by Ocean Wise and local partners to fill in data gaps identified by the Department of Fisheries and Oceans Canada, and contribute to the development of management strategies to better support at-risk populations. So far, researchers have collected 68 samples from killer whales and humpback whales.
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The next step in this study is to look at using these methods for humpback whales as well learn more about these species’ prey.
“A lack of knowledge is a threat to these species in and of itself,” says Robinson. “If we don’t know what they’re eating, where they’re eating, etcetera, we don’t know how to protect them.”
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