础濒补蝉办补鈥檚 was home to beluga whales in the late 1970s, but today the population hovers around 300. Despite almost two decades of recovery work, the whales aren鈥檛 bouncing back. The Cook Inlet belugas are likely struggling under multiple pressures, including increasing human noise. Researchers are working on deciphering whale-whale communication to better account for the impact of noise on this vulnerable population.

In a new study, 爱豆社区 scientists eavesdropped on Cook Inlet belugas, recording more than 1,700 calls representing 21 different behavioral encounters. This work builds on a 2023 study 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 is limited.

Beluga whales use vocalizations to socialize, stick together and avoid danger. The new study, , investigated the behavioral, social and environmental contexts in which the whales produce various calls.

鈥淲e knew that human-generated noise was masking their calls, but we didn’t know what those calls were used for,鈥� said, a UW doctoral student in aquatic and fishery sciences. 鈥淭his study gave us important insights into the world of beluga communication and how it is disrupted by industry and development.鈥�

They found that Cook Inlet belugas use a specific type of call 鈥� a combined call 鈥� when calves are present. Combined calls were one of the call types that got drowned out by shipping noise in the 2023 study, suggesting that shipping noise could be disrupting communication with calves. If mothers and calves can鈥檛 remain in contact, it could spell trouble for the young whales.

鈥淲e don鈥檛 have the data to directly connect noise and calf separation,鈥� Brewer said, 鈥渂ut if a mother whale can鈥檛 acoustically keep in contact with her calf, that could be a huge problem.鈥�.

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 big group, perhaps to avoid talking over each other.

In Cook Inlet, where the whales live year round, silty glacial water gets 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.

鈥淭heir main foraging hot spots 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鈥檚 tricky for them and noise pollution is far from the only threat,鈥� Brewer said.

Beluga whales in the St. Lawrence Estuary in Eastern Canada 鈥� also very noisy 鈥� have evolved to , perhaps in response to lower frequency anthropogenic noise. They also make their when it’s noisy, just like two people conversing at a party would.

In the Puget Sound region, where the endangered Southern Resident killer whales live, 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 .

鈥淭he Port of Alaska could explore similar strategies to mitigate the impact of industry,鈥� Brewer said. 鈥淲e can鈥檛 halt shipping, but we鈥檙e trying to understand what we can do to manage these critical habitats, especially when the animals are nearby.鈥�

Co-authors include , a UW assistant professor of aquatic and fishery sciences;聽 , a UW professor of aquatic and fishery sciences; , a UW assistant professor of aquatic and fishery sciences; , a research scientist in the UW Cooperative Institute for Climate, Ocean, & Ecosystem Studies; of NOAA; Christopher Garner and Andrea Gilstad of the Air Force Conservation Department.

This study was funded by 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.

For more information, contact Brewer at arialb@uw.edu.聽 聽

are highly social and vocal marine mammals. They use acoustics to navigate, find prey, avoid predators and maintain group cohesion. For 础濒补蝉办补鈥檚 critically endangered population, these crucial communications may compete with a cacophony of noise from human activities.

New research from the 爱豆社区, the National Oceanic and Atmospheric Administration鈥檚 Alaska Fisheries Science Center and the Alaska Department of Fish and Game is the first to document the complex vocal repertoire of the Cook Inlet beluga whale population. It is also the first to quantify how ship noise may be masking specific beluga calls in this region.

The , published Nov. 30 in the Journal of the Acoustical Society of America, finds 41 distinct types of calls, of which 18 are unique to this population. It also finds that commercial ship noise completely masks these whales鈥� most commonly used calls.

鈥淭he core critical habitat for these whales is a very noisy area. Commercial shipping, an international airport, military operations and gas and oil exploration are all concentrated there,鈥� said lead author , a doctoral student in the at the UW who did the work in collaboration with NOAA Fisheries鈥� .

鈥淎 fundamental knowledge gap for the Cook Inlet beluga population is how they communicate important information. The first step is to describe their vocal repertoire,鈥� she added. 鈥淲ith that information, we can begin to understand if their communication is impacted by human-caused noise.鈥�

Twenty-one populations of belugas are recognized worldwide, including five distinct populations in Alaska. The geographically and genetically isolated Cook Inlet beluga population is the smallest, recently estimated at just . Cook Inlet beluga whales live exclusively in their namesake waters alongside Anchorage, the state鈥檚 largest city and busiest port.

The Cook Inlet beluga whale population was listed as endangered under the Endangered Species Act in 2008. A 2016 recovery plan ranked three threats as the highest level of concern, one being human-caused noise. Commercial shipping is the most prominent noise source within Cook Inlet, particularly in the upper inlet where most of the federally-designated critical habitat is located.

鈥滱ll of that human-caused noise means the belugas may not hear critical communications from each other, such as predator alarm calls or a mother calling to her calf,鈥� Brewer said.

While all whales are affected by noise, Cook Inlet belugas may be particularly vulnerable to noise as a stressor.

鈥淐ook Inlet is extremely turbid year-round from glacial runoff. It looks like chocolate milk,鈥� Brewer said. 鈥淎coustic communication is extremely important for this population since visibility is so poor. And, unlike other, higher-Arctic beluga populations, this population is non-migratory, so they are exposed to this noise year-round.鈥�

Cook Inlet鈥檚 extreme turbidity, dramatic tides, rapid currents and seasonal ice cover make it an extremely challenging place to study belugas. One way scientists can monitor these highly vocal whales is through sound.

The Cook Inlet Beluga Acoustics Program has been deploying bottom-mounted passive acoustic recorders to monitor belugas and human-caused noise since 2008. The study focused on recordings of beluga whale calls from 2018 to 2019.

鈥淯ntil now, we did not have a quantified measure of masking by ship noise on Cook Inlet beluga communication. We knew this was a potential disturbance mechanism to focus our research efforts, but we were lacking a good understanding of what vocalizations are most important for beluga,鈥� said co-author , a research scientist at the UW-based Cooperative Institute for Climate, Ocean and Ecosystem Studies who manages the acoustics monitoring program. 鈥淭his study provides the first two steps into this direction: We now have a solid understanding of key vocalizations for this population, and how each ship transit is affecting beluga vocal exchange in the core area of their critical habitat.鈥�

For the new study, scientists analyzed recordings at two critical habitat locations: Susitna River, just outside of Anchorage, and Trading Bay, farther out in the inlet.

They classified beluga vocalizations into three broad categories 鈥� whistles, pulsed calls and combined calls 鈥� and then further into 41 unique call types.

鈥淚鈥檝e spent thousands of hours listening to this population. Anytime I find a new call type, it鈥檚 really exciting,鈥� Brewer said, 鈥淓avesdropping on their world is really fascinating.鈥�

The study found that the Cook Inlet beluga population, like other beluga populations, has a rich and complex repertoire. Vocal repertoire has been documented for eight of the 21 populations of belugas worldwide. Results from this study support the hypothesis that some call types are shared across populations, while others are unique.

Of the 41 types of calls the authors documented in the Cook Inlet population, 18 were not documented in any other population; 16 were documented in some but not all of the previously studied populations; and seven were common to all populations studied so far.

鈥淒ifferences in vocal repertoire among different beluga populations may be driven by unique evolutionary, environmental or cultural influences,鈥� Brewer said. 鈥淭he divergence of the Cook Inlet vocal repertoire may be in part due to the population鈥檚 long-term geographic and genetic isolation.鈥�

The researchers next looked at how the most commonly-used call types may be masked by human-caused noise. They focused on commercial ship noise, which is the most prominent noise type in Cook Inlet.

Analysis found that all seven of the most commonly-used call types in the Cook Inlet beluga vocal repertoire were partially masked by the time a commercial ship was within about 10 miles (17 kilometers) of the study site. Calls were completely masked when the vessel was closest to the site during the transit through the designated shipping lanes.

Roughly 486 commercial ships use the Port of Alaska annually, with an average of 8-10 ships coming and going per week. It is estimated that each ship passage will mask beluga communication at the study site for 1 hour and 50 minutes on average.

鈥淥ur results suggest that every time a commercial vessel transits through the Port of Alaska shipping lanes, Cook Inlet beluga communication could be heavily impacted within their core habitat,鈥� Brewer said.

鈥淗umans are such a visual species. It鈥檚 hard for us to comprehend how noisy it is under the surface of the ocean and how much noise impacts marine mammals such as belugas. We hope our findings will lead to further studies to better inform management about these types of human-caused impacts.鈥�

The research was funded by NOAA Fisheries, Hilcorp Alaska LLC, Georgia Aquarium, Shedd Aquarium, the SeaWorld-Busch Gardens Conservation Fund and the H. Mason Keeler Endowed Professorship in Sports Fisheries Management at the UW.

Other co-authors are faculty members and in the UW School of Aquatic and Fishery Sciences; and Tom Gage at the Alaska Department of Fish and Game.

For more information, contact Brewer at arialb@uw.edu or Castellote at manuelcm@uw.edu.

Adapted from a NOAA .