Beluga whales, often referred to as the “canaries of the sea” due to their highly vocal nature, thrive in the frigid, ice-covered waters of the Arctic and sub-Arctic. These pure white marine mammals possess unique biological and behavioral adaptations that allow them to inhabit one of the planet’s most challenging environments. Among their most peculiar observed behaviors is the intentional consumption of or mouthing of sea ice, a practice that initially appears counterintuitive for a creature surrounded by water. Scientists have moved beyond simple curiosity to investigate the specific, complex reasons why this intentional interaction with frozen water is a systematic behavior in their lives. The underlying scientific explanations range from a biological necessity for survival in a saltwater habitat to a means of supplementing their diet and providing behavioral enrichment.
Where and When Belugas Interact With Ice
Belugas are strongly associated with sea ice, utilizing high concentrations of it for much of the year as a refuge and foraging habitat. Their lack of a dorsal fin is a specific adaptation that allows them to navigate and swim effectively beneath the ice canopy. This smooth back enables them to access breathing holes, or polynyas, without the risk of their appendage getting caught, a strategy also used to evade their primary predator, the orca whale.
The behavior of eating ice is most frequently documented during the long winter months or the transition periods of freeze-up and break-up. At these times, belugas are often found in areas with heavy ice coverage, such as the edge of the permanent ice pack or near river estuaries where ice is forming. Observations show that they target particular forms of ice, sometimes seeming to mouth small chunks of consolidated, older ice rather than newly formed, highly saline ice. This seasonal and selective interaction suggests a deliberate purpose tied to the physical properties of the ice itself.
The Critical Need for Freshwater Intake
The primary and most widely accepted scientific reason for belugas eating ice relates to their physiological need for freshwater in a highly saline environment. Like all marine mammals, belugas do not drink seawater because the high salt content would require more energy and water to excrete than the water itself provides, leading to dehydration. This biological challenge is known as osmoregulation, the process of maintaining a proper balance of water and salt within the body.
In the wild, belugas obtain most of their necessary water from the food they consume, as the fish and invertebrates they eat contain relatively low-salinity body fluids. However, periods of low foraging success or migration may necessitate an alternative source of hydration. Sea ice provides this alternative because of a process known as brine rejection that occurs when seawater freezes.
As the water molecules crystallize into a hexagonal lattice structure, salt ions are physically excluded from the ice crystal structure. This expulsion of salt results in ice that is significantly fresher than the surrounding ocean water, often containing up to 70 to 90% less salinity. Over time, gravity drains the remaining pockets of concentrated salt water, or brine, from the ice, especially in multi-year ice. By consuming or scraping older, consolidated ice, belugas can access these relatively pure pockets of frozen freshwater, effectively supplementing their hydration requirements far away from river mouths or other natural sources of liquid fresh water.
Accessing Essential Trace Minerals
A compelling secondary hypothesis suggests that the consumption of ice acts as a unique means for belugas to acquire essential trace minerals that may be scarce in their typical prey at certain times of the year. Arctic sea ice is not merely frozen water; it is a complex ecological platform that traps particulate matter from both the water column and the atmosphere. This trapped material includes wind-blown dust, sediments, and, most importantly, microalgae.
Ice-bound microalgae, such as diatoms, form the base of the Arctic food web and are known to concentrate various elements, including iron, zinc, and manganese. These elements are vital for metabolic functions but might not be consistently available in the beluga’s diet, particularly during periods when prey availability or type shifts. By ingesting the ice, the whales may be engaging in a form of geophagy, the consumption of mineral-rich earth, to supplement these micronutrients directly from the trapped biological and geological particulates.
This behavior allows the whales to bypass the entire food chain to access concentrated nutrients that have settled on or within the ice structure. The mineral content of the ice can vary significantly based on location and season, making it a potentially rich, albeit temporary, source of necessary trace elements. This suggests that the ice serves not only as a source of water but also as a supplemental nutritional delivery system for elements otherwise difficult to obtain.
Non-Nutritional Functions of Ice Consumption
Beyond the biological needs of hydration and nutrition, belugas appear to interact with ice for several non-nutritional, behavioral reasons. One theory is that the ice serves a function for dental maintenance and oral hygiene. By intentionally mouthing and crunching on pieces of ice, the whales may be using the abrasive texture to scrape away plaque or debris from their teeth. This action helps keep their oral cavity healthy, which is important for a species that relies on its teeth to grasp prey like fish and squid.
Ice also provides an important source of enrichment and play, especially for younger belugas. Highly intelligent and social, belugas are frequently observed manipulating objects in their environment, and chunks of ice become novel toys for exploration and social interaction within their pods. The ice can also be used for physical grooming, as the whales rub their bodies against the rough surface to help shed old skin. This physical interaction with the ice helps remove the yellowish layer of skin that accumulates over the winter months, revealing the fresh, white skin underneath.