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Cook Inlet belugas swimming in northern Cook Inlet, near Anchorage, Alaska.
Photo Credit: Arial Brewer
Scientific Frontline: Extended "At a Glance" Summary: Cook Inlet Beluga Whale Acoustic Communication and Anthropogenic Interference
The Core Concept: University of Washington researchers have deciphered the specific vocalizations of endangered Cook Inlet beluga whales to map the behavioral context of their calls and determine how human-generated marine noise disrupts their communication network.
Key Distinction/Mechanism: Unlike broad observational conservation metrics, this research employs detailed bioacoustic analysis to isolate specific vocal patterns, revealing that "combined calls"—which are used specifically when calves are present—are the exact frequencies being masked by commercial shipping noise.
Major Frameworks/Components:
- Acoustic Masking: The process by which low-frequency anthropogenic noise from regional shipping, ports, and military bases drowns out critical biological communication.
- Behavioral Context Mapping: The correlation of fluctuating call rates with specific environmental triggers (e.g., incoming tides) and social dynamics (e.g., transitioning from socializing to traveling).
- Combined Calls: Complex, distinct vocalizations utilized by adults in the presence of calves to maintain contact in highly turbid, silty glacial waters.
- Density-Dependent Vocalization: The observation that individual call rates decrease as group size increases, likely a mechanism to avoid acoustic signal overlap.
Branch of Science: Marine Biology, Bioacoustics, Behavioral Ecology, Conservation Biology
Future Application: The research provides a scientific foundation for implementing dynamic, localized noise mitigation policies, such as mandating vessel speed reductions in critical foraging habitats near Anchorage, mirroring successful protocols currently utilized for Southern Resident killer whales in the Puget Sound.
Why It Matters: The Cook Inlet beluga whale population has severely declined from nearly 1,300 in the 1970s to approximately 300 individuals. Identifying the exact mechanisms of acoustic disruption—specifically the potential for noise-induced mother-calf separation—is critical for adapting human industrial activity to prevent the extinction of this geographically isolated population.
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| Cook Inlet beluga mother and calf in Eagle Bay, Alaska. Photo Credit: Arial Brewer |
Alaska’s Cook Inlet was home to nearly 1,300 beluga whales (Delphinapterus leucas) in the late 1970s, but today the population hovers around 300. Despite almost two decades of recovery work, the whales are not recovering. The Cook Inlet belugas are likely struggling under multiple pressures, including increasing anthropogenic noise. Researchers are working on deciphering whale-to-whale communication to better account for the impact of noise on this vulnerable population.
In a new study, University of Washington (UW) scientists eavesdropped on Cook Inlet belugas, recording more than 1,700 calls representing 21 different behavioral encounters. This work builds on previous research showing that noise from commercial shipping, the primary industry in the region, masks common beluga calls. Although many marine mammals rely more on sound than sight, our understanding of acoustic communication among these animals remains limited.
Beluga whales use vocalizations to socialize, stick together, and avoid danger. The new study, published May 7 in Behavioral Ecology and Sociobiology, investigated the behavioral, social, and environmental contexts in which the whales produce various calls.
“We knew that human-generated noise was masking their calls, but we didn’t know what those calls were used for,” said Arial Brewer, a UW doctoral student in aquatic and fishery sciences. “This study gave us important insights into the world of beluga communication and how it is disrupted by industry and development.”
They found that Cook Inlet belugas use a specific type of call—a combined call—when calves are present. Combined calls were one of the call types that were drowned out by shipping noise in previous observations, suggesting that shipping noise could be disrupting communication with calves. If mothers and calves cannot remain in contact, it could spell trouble for the young whales.
“We don’t have the data to directly connect noise and calf separation,” Brewer said, “but if a mother whale can’t acoustically keep in contact with her calf, that could be a huge problem.”
Researchers also found that calling between whales increased right before a behavioral change in the group, such as a transition from socializing to traveling, and when the tide was coming in. The call rate for individual whales decreased as group size increased, suggesting that individuals call less in a large group, perhaps to avoid vocalizing simultaneously.
In Cook Inlet, where the whales live year-round, silty glacial water is churned up by powerful currents and dramatic tides. Beluga whales likely moved in after the last Ice Age, roughly 10,000 years ago. Vocal communication and echolocation, a navigational strategy used by bats and some whales, have allowed them to survive in this extreme environment, but human noise presents a newer challenge.
“Their main foraging hotspots for salmon are in the northern part of the inlet, near Anchorage, and in close proximity to the airport, the Port of Alaska, and the military base. I think there are ways to adapt, but it’s tricky for them, and noise pollution is far from the only threat,” Brewer said.
Beluga whales in the St. Lawrence Estuary in eastern Canada—also a highly noisy environment—have evolved to communicate at very high frequencies, perhaps in response to lower-frequency anthropogenic noise. They also make their calls louder when it is noisy, just as two people conversing at a party would.
In the Puget Sound region, where the endangered Southern Resident killer whales (Orcinus orca) live, large ships are asked to slow down when whales are reported in the area. Smaller ships are legally required to keep their distance and slow down within half a mile of the whales. This program was introduced after researchers demonstrated that shipping noise interferes with hunting.
“The Port of Alaska could explore similar strategies to mitigate the impact of industry,” Brewer said. “We can’t halt shipping, but we’re trying to understand what we can do to manage these critical habitats, especially when the animals are nearby.”
Funding: This study was funded by the UW School of Aquatic and Fishery Sciences, the Cooperative Institute for Climate, Ocean, and Ecosystem Studies under a NOAA Cooperative Agreement, and the H. Mason Keeler Endowed Professorship in Sports Fisheries Management.
Published in journal: Behavioral Ecology and Sociobiology
Title: Cook Inlet beluga whale calling varies by group characteristics, behavior, and tidal state
Authors: Arial M. Brewer, Amy M. Van Cise, Christopher Garner, Andrea Gilstad, Manuel Castellote, Sarah J. Converse, Kimberly T. Goetz, and Andrew M. Berdahl
Source/Credit: University of Washington | Gillian Dohrn
Reference Number: mb051326_01
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