Pacific Grey Whales: The causes of the roughly 40% reduction in the number of Pacific grey whales that migrate along the Oregon Coast each winter and spring on their route from Baja, Mexico to the Arctic are being researched by scientists. The loss of sea ice due to human-caused climate change and the impact of warmer temperatures on Arctic feeding grounds make food scarcity one of the main suspects.
According to recent data from the National Oceanic and Atmospheric Administration, or NOAA, the whale population peaked at roughly 27,000 in 2016 but has since fallen to 16,650.
The birth rate has decreased by 40% in the past year alone, reaching its lowest point since records have been kept in 1994.
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40% Decline In The Population Of Pacific Grey Whales
In 2019, when 120 dead grey whales showed up on beaches from California to Alaska, NOAA proclaimed an “unusual mortality episode.” Approximately 600 dead grey whales have washed ashore since then. According to NOAA, many seemed underweight.
The eastern North Pacific grey whale is prone to large birth rate swings and extraordinary mortality episodes, but the current trend is lasting longer than before, and some experts worry that populations may not recover to levels observed in the past.
Scientists from Oregon State University have found that one population of whales no longer migrates to the Arctic in search of food, preferring to remain around the shores of Oregon, Washington, and British Columbia.
There are more deaths and fewer births than ever before, according to experts, but there is data that suggests that the scarcity of food is having an impact on people’s health. Due to the intimate relationship between adult whale survival and reproduction, calf birth rates often decrease when there is an unexpected death event. Fewer births can occur as a result of whales delaying reproduction and being in worse health.
According to NOAA data, the eastern North Pacific grey whale population last saw a major reduction similar to the current one in the late 1980s. In the years that followed, it recovered and reached new heights, and in 1994, Pacific grey whales were delisted as an endangered species. The population experienced another 25% fall in 1999 and 2000 before increasing to its peak in 2016.
Joshua Stewart is an assistant professor at Oregon State University’s Marine Mammal Institute. He previously worked for NOAA where he studied Pacific grey whale populations and calf birth rates. In an effort to comprehend grey whale population swings, death events, and any patterns that might link them, he has reviewed population data collected since 1967.
According to him, the population appears to decline every 10 to 20 years and then quickly rebound in the past.
Given the significant changes taking place to their primary feeding grounds up in the Arctic, he added, “what we’re worried about today is if they’re still going to be able to do that, to recover.”
Stewart claimed that other possible explanations for the losses, such as whales being hit by vessels or entangled in fishing gear, have been researched.
The Arctic’s current conditions, which are likely the product of climate change, appear to be the primary cause of these large die-offs, according to Stewart.
Gray whales consume a variety of foods during their 10,000-mile migration from Mexico to Alaska, but the majority of their summer eating occurs in the Arctic.
The little, spineless crustaceans known as amphipods, which resemble shrimp and are found near the seafloor, are what the Pacific grey whales eat there.
The food chain up there is heavily dependent on the ice, according to Stewart. The algae that grow on the ice eventually die, drop to the bottom and connect all of that productivity to the ocean floor, which the whales then eat. Therefore, their food supply is affected when that is disrupted.
Extreme sea ice cover changes may cause unexpected death events to occur more frequently and for a longer period of time.
“This one appears to be sticking around, perhaps longer than the earlier ones. They may have a harder time recovering from them if there isn’t enough space in the Arctic to support this many whales, as has been the case with the most recent one in 2000, he added.
A significant number of Pacific gray whales have died and washed ashore from California to Alaska and birth rates are down 40% in the last year, report @ORCapChronicle and @statesnewsroom.https://t.co/tBtYcgAojz
— Sean Scully (@EditorSean) November 21, 2022
Summer Residents Of Oregon
The Pacific Coast Feeding Population, also known as the summer residents, is a group of roughly 200 Pacific grey whales that no longer visit the Arctic. Rather, they shorten their journey and forage in the region extending from northern California to British Columbia.
The majority of these whales have only been followed in the past ten years, so scientists are unsure if they are doing this for the first time or if it was something they were already doing before commercial whaling nearly wiped off the grey whale population.
Since around 2009, researchers at Oregon State University have been monitoring them. Since 2016, they have collected fecal samples and taken aerial photographs to evaluate the whales’ physical states and the amounts of four hormones that impact the whales’ reproductive health, the balance of their diet, and their degree of stress.
According to Lisa Hildebrand, an OSU Ph.D. student who is studying the group with researchers from the Marine Mammal Institute, “It’s a gold mine of data.” Their populations have changed, but not as dramatically as whales that have historically visited the Arctic.
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Historically, the latter had stronger bodies than those who stayed in the Northwest, but that’s changing now: The body condition of the Pacific Coast Feeding Group has improved through time, growing larger and rounder, while the body condition of whales migrating all the way to the Arctic has deteriorated.
Scientists have discovered that the whales that remain near the Pacific Coast are “flex-feeders,” adjusting to a wider variety of food sources than in the past, according to Hildebrand. The diverse species that whales eat off the coast of Oregon are more nutritional and energy-rich than those in the Arctic, but they are only readily available for a short time in the summer as opposed to the extended availability in the Arctic summer from May through September.
According to Hildebrand, researchers are finding that whales may be assessing the benefits and drawbacks of traveling all the way to the Arctic.
She remarked, “Perhaps whales can take advantage of the short-term, high-quality prey here.
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