Killer whales swimming off the San Juan Islands, Washington
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Killer whales off the west coast of the United States may be inbred enough to hinder population recovery. Researchers found these inbred killer whales to have short lifespans, and believe the females die before reaching their peak breeding age.
Compared to other killer whales (killer whale), this group known as the Southern Resident Population is strange. First of all, its members live year-round in the North Pacific, while most other killer whales migrate around the world. They also eat exclusively fish, avoiding mammals such as sea lions, which most killer whales include in their diet.
And unlike their cousins, the Southern population is declining. By the 1970s, commercial fishing and water pollution had drastically reduced the number of killer whales worldwide. Habitat and hunting protections have since pushed the species forward toward recovery, but the southern resident population has not followed suit.
“Many North Pacific killer whale populations have tripled,” says Marty Cardos of the National Oceanic and Atmospheric Administration (NOAA). “He’s one of the few exceptions for Southerners.” The group, in 1974 he consisted of 71, peaked at 97 in 1996, and now he’s 70. reached the table.
Kardos and his colleagues sequenced the genomes of 100 live and dead killer whales from a southern resident group. This provided an overall picture of the genetic diversity of the group. The more similar the genomes, the more likely they are inbred.
Comparing the genomes of these whales with the genomes of 50 other killer whales around the world found that Southern residents had the highest levels of inbreeding and the lowest levels of genetic diversity. They examined the genome and lifespan of individual killer whales and found that inbred animals died earlier. A female killer whale doesn’t reach peak breeding until she’s around age 20, so Kardos suspects female whales may die before or during the peak of their breeding season. .
According to Cardos, different groups of orcas rarely mix with each other, largely because of differences in social structure. “They eat different things and speak different languages,” he says Kardos. But breeding between different populations has happened in the past, and “it could happen again,” he says.
Until then, we need to focus on providing the conditions for southern killer whales to thrive by protecting the waters and limiting pollution, commercial fishing and shipping traffic, Cardos said.
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