Killer whales get bonanza meals in global sea of change

News of the demise of roughly 40 orcas is rare but scientists are concerned the real number could be three times that estimate While the dramatic population decline of Killer Whales in the North…

Killer whales get bonanza meals in global sea of change

News of the demise of roughly 40 orcas is rare but scientists are concerned the real number could be three times that estimate

While the dramatic population decline of Killer Whales in the North Pacific in recent years is well known, new research is shedding light on a new phenomenon for which the region of concern remains largely unknown: the discovery of bonanza killer whale prey around the clock.

Data from multiple sources discovered up to 11 pods collectively eating three times as much salmon as a single pod in areas where the population of the largest member of the dolphin family had fallen to near historic lows.

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While the population of Killer Whales in the area is officially known as Pacific white-sided dolphins, the sleek lumbers also have the black markings of killer whales.

An estimated 40 individual pods are believed to live on the island chain that connects the North Pacific Ocean to the Arctic Ocean and has been home to extensive research on the mysterious and spectacular creatures since the early 1900s.

The research published in Scientific Reports relied on extensive coverage of the migration of global fisheries and notes from the Japanese government and Department of Fisheries and Aquaculture researchers to determine that the abundance of killer whales in the region has risen 300% over the past decade, “exceeding all previous estimates”.

“I’ve worked with killer whales for over 20 years and I’ve always thought we knew a lot about them,” said James Seymour, a doctoral student at the National Oceanic and Atmospheric Administration’s Alaska-based research center. “But this paper shows that there’s so much more data that still remains to be collected.

“The way we would often measure the decline or increase of killer whales, the populations aren’t very well understood. There is no neat, linear function for mortality data, with good track records dating back to 1936. And the anthropogenic threats such as toxic exposures or fishing gear can be important. But what’s surprising is that there’s also no reliable data on prey abundance or if there are interactions between killer whales and other waterfowl or prey species,” Seymour added.

Between 2010 and 2015, it was discovered that the prey was off the charts, with 65% more biomass in the Western Chukchi sea area than the maximum levels in the 2005 to 2010 time frame. That year was defined as the lowest population of killer whales living in the North Pacific, noted the authors, with 46 pods reported as recovering from either low or no hunting.

Last summer, a navy cargo ship was attacked by killer whales and destroyed at the bottom of the Bering Sea. Photograph: NOAA

The same year that the data was collected, 10 pods fed on 10 separate occasions, and 10 pods met at least once. The scientists found that great blue herons, snowy egrets, black ducks, crested newts, tanagers, salmon, and a colony of black-crowned night herons were feeding on killer whales. But more whales than expected were participating in the bonanza in northern areas of Asia where mostly bound seals typically hang out.

Data from traditional maritime records also showed up-to-date whale encounters with another pod for the first time since 2006.

“Some whale encounters will happen in unison – sometimes two pods have spotted each other in the same area and others will come in from different locations,” said Seymour. “In these cases, we can rely on previous encounters to determine if the two pods fed each other, or if there were interactions with other pods.”

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While such eventful run-ins are rare, there were four reported in one year. The researchers are concerned that in numbers that high, the real number of Killer Whales in the region could be three times the number reported.

“There is a looming question as to how we are going to define the number of animals that may be present when we catch up with them on beaches. If they are all working together, we have an even bigger challenge in estimating their number. I think we are going to need a better measure than we have now,” said Seymour.

While scientists have faced the reality of rapid change in the species, none had witnessed such a large rise in prey at a time the region is experiencing rapid reduction in sea ice and snow cover.

“We have seen temperature rise in these large areas of the world that are already warming. We now have observations of increase in lethal force. Yet we also have current evidence that they are increasing in population

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