A troubling trend has emerged among the gray whales frequenting the Pacific Northwest coast: they have been shrinking in size over the past 20 to 30 years. This startling discovery is detailed in a new study led by researchers at Oregon State University (OSU).
Significant decrease in whale length
The study, which focused on a subgroup of approximately 200 gray whales known as the Pacific Coast Feeding Group (PCFG), found that these whales have decreased in body length by an average of 13% since around the year 2000. Unlike the majority of the Eastern North Pacific (ENP) gray whale population, which migrates to the Arctic, the PCFG spends its summers feeding in the warmer, shallower waters along the Oregon coast.
Methodology and findings
Researchers from OSU’s Marine Mammal Institute have been studying this PCFG subgroup since 2016, employing drones to measure the whales’ size. Their findings indicate that a gray whale born in 2020 is expected to reach an adult body length approximately 1.65 meters (5.5 feet) shorter than a whale born before 2000. This significant reduction represents over a 13% decrease in the total length of these whales, which typically grow to 38 to 41 feet long.
“This could be an early warning sign that the abundance of this population is starting to decline or is not healthy,” said KC Bierlich, co-author of the study and an assistant professor at OSU. “And whales are considered ecosystem sentinels, so if the whale population isn’t doing well, that might say a lot about the environment itself.”
Potential implications for whale health and reproduction
The researchers express concern that this shrinking size could have cascading negative effects on the whales’ health and reproduction. The study also delved into changes in ocean upwelling and relaxation patterns, which affect the availability of the whales’ prey. The decline in whale size coincided with shifts in these oceanographic cycles, which the researchers suspect may be linked to climate change impacts on wind and temperature in the Northeast Pacific.
“Without a balance between upwelling and relaxation, the ecosystem may not be able to produce enough prey to support the large size of these gray whales,” said Leigh Torres, co-author of the study and director of OSU’s GEMM Lab.
Future research directions
Moving forward, researchers aim to further investigate the environmental drivers behind the shrinking size of the PCFG gray whales. Understanding these factors is crucial for grasping the broader implications for the health of this whale population and the overall marine ecosystem.
This study highlights a significant environmental concern that requires immediate attention. The shrinking size of the PCFG gray whales could be a harbinger of broader ecological issues, underscoring the need for continued research and proactive measures to protect these vital marine mammals and their habitats.
