Impact of Arctic Variability on Gray Whale Populations

by Tatsuya Nakamura
Arctic gray whale die-offs

Since the 1980s, the fluctuating Arctic conditions have instigated significant die-offs in the eastern North Pacific gray whale population. This has been confirmed by a new research study. In instances of these die-offs, one of which commenced in 2019 and is still ongoing, the population of gray whales diminished by as much as 25% within a span of several years, according to Joshua Stewart, the primary author of the study from Oregon State University’s Marine Mammal Institute.

Such dramatic fluctuations in the gray whale population are unexpected, especially for a species known for its longevity. Factors such as reduced availability of prey in the Arctic and obstructions caused by sea ice have led to swift and severe shocks to the gray whale numbers.

Despite their long life and mobility, gray whales are vulnerable to the effects of climate change, particularly when there’s a sudden decrease in the quality of their prey, which has substantial consequences on their population numbers.

Eastern North Pacific gray whales have recovered from the impact of commercial whaling, approximating their original numbers. However, as their numbers grow closer to the capacity that their Arctic feeding areas can sustain, they’ve become more susceptible to environmental variations, mainly because of the competition for finite resources.

The transient unfavorable Arctic conditions that caused die-offs in the 1980s and 1990s were temporary, allowing the population to recover swiftly. However, Joshua Stewart suggests that the reality of a thriving baleen whale population is more complex than previously understood. Instead of a stable population, fluctuations are observed, reflecting the rapid changes in oceanic conditions.

Migrating over 12,000 miles annually, the eastern North Pacific gray whales, numbering around 14,500, move from the temperate waters off Baja California, Mexico during winter to the chilly, nutrient-rich Arctic waters in the summer. The National Oceanic and Atmospheric Administration Southwest Fisheries Science Center has been monitoring these whales since the 1960s, offering unparalleled insights into their population dynamics.

Such long-term studies are crucial, as highlighted by Dave Weller of the Southwest Fisheries Science Center. The extensive data has allowed scientists to observe the impacts of climate change on this pivotal species.

After almost facing extinction, the eastern North Pacific gray whale population’s quick recovery post-whaling has been seen as a conservation triumph. However, the onset of a large number of strandings in 2019 prompted deeper analysis into potential causes. Stewart’s research, combined with environmental Arctic data, highlighted the connection between die-offs and factors like sea ice levels in the Arctic and the primary food sources of gray whales.

Reduced sea ice during summer in the gray whales’ Arctic feeding zones offers better foraging, aiding their population. Nonetheless, the continuous reduction in sea ice, an outcome of rapid climate change, might not favor gray whales in the long run. Their primary food, benthic amphipods, is also influenced by sea ice conditions. A decline in ice results in fewer algae descending to the seafloor, leading to a less nourishing environment for amphipods.

The diminished food availability is a direct cause of gray whale die-offs. The ongoing event is more prolonged than previous ones. Stewart posits that the protraction might be due to the effects of climate change causing a consistent decrease in food quality.

However, given their long evolutionary history, gray whales have adapted to multiple environmental shifts. Stewart believes that while they may not go extinct due to climate change, a significantly warmed Arctic Ocean might not be able to sustain as many gray whales as it did in recent history.

Reference: The findings were detailed in an article titled “Boom-bust cycles in gray whales associated with dynamic and changing Arctic conditions” published on 12 October 2023 in the journal Science.

Frequently Asked Questions (FAQs) about Arctic gray whale die-offs

What has caused significant die-offs in the gray whale population since the 1980s?

Arctic variability and changing conditions have led to major die-offs in the eastern North Pacific gray whale population.

How much has the gray whale population reduced during these die-offs?

During these mortality events, the gray whale population has seen reductions of up to 25% within a few years.

Are gray whales adaptable to changing conditions?

While gray whales are known for their adaptability, the rapid changes brought about by climate change, especially concerning their prey’s availability, present unprecedented challenges.

Have the gray whales recovered from the effects of commercial whaling?

Yes, the eastern North Pacific gray whales have rebounded, with their current numbers potentially reflecting those before commercial whaling.

How does reduced sea ice in the summer benefit the gray whales?

Reduced summer sea ice in the gray whales’ Arctic feeding areas provides increased foraging opportunities, which can be beneficial for their population.

How is the ongoing die-off event different from the previous ones?

The most recent die-off event has lasted longer than previous events, with factors like climate change leading to a continuous decline in prey quality being potential contributors.

Is there a risk of gray whales going extinct due to climate change?

While gray whales have adapted to environmental changes over hundreds of thousands of years, a significantly warmer Arctic Ocean might not sustain as many gray whales as it did in recent times, though outright extinction due to climate change is considered unlikely.

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Mike T. October 13, 2023 - 2:06 am

So gray whales are being affected by climate change too huh? its sad to see the kind of impact we’re having on these majestic creatures…

JennaB October 13, 2023 - 3:04 am

i read about this the other day. The arctic conditions are changing faster than we think. Its concerning for all marine life not just whales.

rj_sporty October 13, 2023 - 4:01 am

I’ve always been fascinated by gray whales. reading this kinda breaks my heart. Hope there’s a way we can reverse some of this damage…

LeonK91 October 13, 2023 - 10:06 am

Can’t believe gray whales have faced such big die-offs. 25% is a huge number. We need to do more to protect our oceans and its inhabitants.

Tasha_M October 13, 2023 - 12:17 pm

wait, so the whales are dying because their food is affected? That’s a domino effect that’s scary to think about. everythings connected.

Dave_theWave October 13, 2023 - 4:42 pm

Saw a gray whale once when I was out at sea. Magnificent! It’s a reminder that our actions have consequences even in places we dont see everyday.


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