Beluga whales, also known as "canaries of the sea" due to their diverse vocalizations, are Arctic and sub-Arctic cetaceans with unique adaptations for survival in icy waters. Their diet is as varied as their calls, playing a crucial role in their overall health and the delicate balance of their ecosystem. This article delves into the dietary habits of beluga whales, exploring what they eat, how they hunt, and the threats they face in securing their food supply.
General Dietary Habits and Hunting Strategies
Beluga whales are opportunistic feeders, meaning their diet depends on their location and the season. They feed in both open water (pelagic) and bottom (benthic) habitats, and in both shallow and deepwater areas, with some recorded diving to more than 350 meters to feed. Belugas tend to hunt alone, but cooperative hunting behaviors have been observed.
A typical hunting sequence for beluga whales includes:
- Searching: Belugas begin by searching for prey with slow, directed movement combined with passive acoustic localization.
- Hunting: Belugas may employ echolocation and suction.
Belugas divide their day between resting and feeding. Their teeth, numbering 36 to 40, are conical and used for grasping prey rather than chewing.
Diet Composition
The diet of beluga whales is diverse, consisting of fish and invertebrates. Some examples of prey include:
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- Fish: Arctic cod, saffron cod, rainbow smelt, walleye pollock, Pacific salmon (especially Coho), capelin, herring, smelt, sole, flounder, sculpin, lingcod, eulachon (hooligan), rose fish, and Greenland halibut.
- Invertebrates: Shrimp, squid, crabs, clams, octopus, sea snails, and bristle worms.
The specific composition of their diet varies depending on their location.
Regional Dietary Variations
- Beaufort Sea: Belugas in the Beaufort Sea mainly eat Arctic cod, staghorn sculpin, shorthorn sculpin, walleye pollock, saffron cod and Pacific sand lance.
- Eastern Chukchi Sea: The most common prey species for belugas in the Eastern Chukchi Sea appears to be shrimp, echiurid worms, cephalopods and polychaetes. The largest prey item consumed seems to be saffron cod.
- Eastern Bering Sea: Beluga whales in the Eastern Bering Sea feed on a variety of fish species including saffron cod, rainbow smelt, walleye pollock, Pacific salmon, Pacific herring.
- Cook Inlet: Cook Inlet beluga whales depend on seasonal runs of anadromous fish for their food, especially eulachon (also known as hooligan) in the spring and salmon in the summer.
The Diet of St. Lawrence Belugas
Research on St. Lawrence belugas reveals a varied diet consisting of fish and invertebrates generally measuring less than 30 cm. The most frequently found prey are bottom-dwelling fish such as cod, hake, and redfish, as well as polychaetes (bristle worms) and small cephalopods such as squid.
Compared to previous knowledge, redfish, American eel, and two species of hake are now present in the contemporary beluga diet. Analyzing stomach contents in beluga carcasses also makes it possible to note seasonal variations, as well as differences in diet between males and females, particularly in summer. Sand lance, eel, rainbow smelt, and Atlantic herring were detected in the beluga diet exclusively in late summer and fall, while other species were detected in spring or fall. Male and female belugas use the multiple habitats of the St. Lawrence differently, leading to differences in diet.
Importance of Diet for Cook Inlet Belugas
Cook Inlet beluga whales depend on seasonal runs of anadromous fish for their food, especially eulachon (also known as hooligan) in the spring and salmon in the summer. Belugas must eat a lot of these oil-rich fish to build up enough blubber to get through winter when food is scarce. Having robust energy reserves is especially important for females who are nursing a young calf all winter.
Threats to Beluga Whale Diet
Numerous factors threaten the beluga whale's food supply and overall health. These include:
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Reduction in Prey
NOAA has identified “reduction in prey” as a threat to Cook Inlet belugas, and recent scientific publications have concluded that if these belugas have enough food, they can better withstand the other threats they face. With ample food, the population’s abundance could also increase by improving their low reproductive rates.
Water Pollution
Water pollution from contaminants has been identified as a threat to belugas. Multiple studies have found pollutants/contaminants in Cook Inlet waters, in the prey of the belugas, and in the belugas themselves. There have also been recent scientific publications suggesting water pollution may be associated with compromised health and low reproductive rates of Cook Inlet belugas.
Climate Change
The impacts of climate change on whales are unknown, but it is considered one of the largest threats facing high latitude regions where many gray whales forage. Most notably, the timing and distribution of sea ice coverage is changing dramatically with altered oceanographic conditions. Any resulting changes in prey distribution could lead to changes in foraging behavior, nutritional stress, and diminished reproduction for beluga whales.
Overfishing
Overfishing, habitat changes, development, and the impacts of climate change can decrease the amount of food available to beluga whales. Without enough prey, belugas might experience decreased reproductive rates and increased mortality rates. Understanding the potential for food limitations to hinder population recovery is especially important for Cook Inlet beluga whales because they live in an area with high human activity.
Conservation Efforts
Several organizations and initiatives are dedicated to protecting beluga whales and their food sources. These include:
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- Alaska Wildlife Alliance (AWA): AWA advocated on behalf of Cook Inlet belugas to the Board of Fisheries, and in 2024 secured 100 more tons of eulachon for Cook Inlet belugas in the Susitna River in spring. AWA has submitted a proposal for funding to coordinate a multi-partner effort to conduct research in the Susitna River to determine the strength of the eulachon run.
- NOAA Fisheries: NOAA Fisheries manages Alaska’s beluga stocks through comanagement agreements with Alaska Native groups.
- Alaska Beluga Monitoring Partnership (AKBMP): Now a NOAA-led Program, AKBMP trains community members on how to become citizen scientists who monitor and collect data about Cook Inlet beluga whales.
The Cook Inlet Beluga Whale: A Case Study
The Cook Inlet beluga whale population is particularly vulnerable. This population experienced a population decline during the 1980s and 1990s. Since 1979, the population has declined 75 percent-from about 1,300 whales to around 300 today. Following this rapid decline, the federal government designated the Cook Inlet beluga population as depleted under the Marine Mammal Protection Act (MMPA) in 2000, and endangered under the Endangered Species Act (ESA) in 2008. The population has yet to recover.
Threats Specific to Cook Inlet Belugas
Cook Inlet beluga whales predominately share the upper and middle portions of Cook Inlet with Alaska’s human population center (Anchorage), transportation hub, and largest concentration of industrial activity.
The reason for the Cook Inlet beluga’s distribution change is unknown, but the quieter Susitna River delta appears to be an important feeding area that continues to be occupied by large groups of belugas during the ice-free period.
Conservation Actions for Cook Inlet Belugas
NOAA Fisheries formed a recovery team of scientists and stakeholders, including Alaska Native partners, the oil and gas industry, fishing group, environmental organizations, the state of Alaska, and other federal agencies to help develop a Cook Inlet beluga whale recovery plan. The recovery plan builds upon scientific studies, traditional knowledge, and other observations and information sources to identify gaps in our knowledge and the research needed to fill those gaps. The recovery plan also identifies specific criteria that will signal the recovery of these animals.