Why Do Walruses Whistle? The Meaning Behind Their Sounds

Walruses whistle as part of an elaborate underwater vocal repertoire that males use primarily during the breeding season, though the full range of walrus sounds extends far beyond whistling. Recorded calls include knocks, strums, bells, grunts, and whistles, each playing a role in a complex acoustic world that researchers are still mapping out. What makes walrus vocalizations particularly fascinating is that they are not random noise: males arrange their calls into structured, repeating sequences that function like songs, while mothers and calves rely on individually distinct calls to find each other in crowded, chaotic herds.

A Surprisingly Varied Vocal Toolbox

If you picture walrus sounds at all, you probably imagine the barking and bellowing they do on land. But the most interesting part of their acoustic life happens underwater. Researchers recording male Atlantic walruses near their haul-out sites have documented at least five distinct call types beneath the surface: knocks, strums, bells, grunts, and whistles.¹ Each of these sounds has a different acoustic profile. Knocks are sharp, impulsive bursts. Strums have a rapid, rhythmic quality. Bells carry a metallic, ringing tone. Grunts sit lower in the frequency range. And whistles, the call that draws the most curiosity, are tonal signals that can cut through underwater ambient noise.

This variety is not accidental. The walrus is the only living member of its family (Odobenidae), and its vocal behavior sits in an interesting evolutionary space between the eared seals, which do most of their courtship calling on land, and the earless seals, which vocalize primarily at sea. Walruses conduct their courtship underwater, which means their sound repertoire has been shaped by the acoustic demands of the ocean environment rather than the open air.² Water transmits sound very differently than air. Low-frequency sounds travel far underwater, and tonal signals like whistles can be detected at greater distances than broadband noise, which may explain why walruses have developed such a range of call types rather than relying on a single all-purpose vocalization.

Breeding Songs and Why Males Sing

The most dramatic use of walrus vocalizations happens during the mating season. Male Atlantic walruses attending herds of females produce complex, stereotyped underwater songs, repeating the same structured sequence of calls continuously while they stay near the herd.³ These are not casual vocalizations. A singing male repeats his particular arrangement of knocks, bells, and other sounds in a highly predictable cycle, and early research showed that the pulse patterns of individual walruses are nearly identical from one vocalization cycle to the next but consistently different from the patterns of other males. One recognizable male’s diving vocalization was identical across two separate years of recording.⁴

This individual consistency matters. In a mating system where females gather in herds and males compete for access, a reliable vocal signature lets both females and rival males identify who is singing. Not every sexually mature male in the area sings, either. Other males in the vicinity may behave as silent herd members, hanging around without vocalizing, or as vocal satellite males orbiting the periphery.³ The male who holds position near the females is the one singing continuously. The structure seems to be: if you can maintain a loud, complex, unbroken song while staying close to the herd, you are advertising your fitness. If you cannot, you lurk at the edges or stay quiet.

Whistles fit into this competitive landscape as one component of these elaborate songs. A whistle that travels well through water and carries an identifiable tonal character could help a singing male broadcast over longer distances, potentially reaching females who are still deciding which male to approach. The exact function of each individual call type within a song remains an open research question, but the overall pattern is clear: the songs exist to signal quality during competition for mates.

Clapping, Knocking, and the Physics of Showing Off

Walrus males do not limit themselves to vocal cord-produced sounds. During the breeding season, they also produce intense impulsive sounds through physical actions. Research on a captive male walrus documented a striking behavior: the animal produced loud, sharp sounds by clapping its flippers together underwater, creating cavitation bubbles that collapsed with a bang. This clapping behavior was exclusively associated with the breeding season, appearing during rut and disappearing outside it, with timing that tracked the animal’s blood testosterone levels.⁵

The regularity of these claps was notable. The researchers hypothesized that the consistent pulse rate could be constrained by the drag of moving flippers through water, or it could be entrained to the animal’s heart rate during submersion. Either way, the result is a metronomic series of intense sounds that a listening walrus could use to judge the producer’s physical condition. A male who can generate louder and more regular claps may be advertising superior body condition, flipper strength, or cardiovascular fitness. The researchers proposed that this clapping could function alongside or even substitute for knocking displays during competition between males, potentially deterring rivals and attracting females within the walrus mating system.⁵

Several other captive males have produced variants of clapping behavior during breeding season while performing their own stereotyped acoustic displays, suggesting this is not a quirk of one individual but a broader behavioral pattern in the species. Whether it occurs commonly in the wild is still being investigated, since recording and observing walruses during the breeding season in Arctic waters is extraordinarily difficult.

How Mothers and Calves Find Each Other

Breeding songs get the most attention, but walrus vocalizations serve a completely different purpose outside the mating context. Mothers and calves use individually distinctive calls to maintain contact with each other, and the system is remarkably precise. Field experiments with Atlantic walruses showed that calves produce barks with consistent individual signatures embedded in their frequency patterns, and mothers responded more strongly to the barks of their own calf than to those of unrelated young.⁶

The key acoustic features that let mothers tell their own calf apart from others relate to frequency modulation and the overall frequency spectrum of the bark. These features are not just individually distinctive; they are also durable over distance. Propagation experiments revealed that barks travel farther over open water than over ice, and the frequency parameters that carry individual identity are highly resistant to degradation as the sound moves through the environment.⁶ In other words, a mother walrus can hear her calf’s bark at a distance and still recognize it as belonging to her offspring rather than someone else’s. For animals that haul out in dense, noisy aggregations of hundreds or thousands of bodies, this acoustic recognition system is essential for keeping mother-calf pairs bonded after separations.

The walrus mother-calf bond is among the longest in pinnipeds, with calves staying dependent for two years or more. Over that period, maintaining reliable vocal contact through crowded haul-outs and murky water is not a luxury. It is a survival requirement. Losing track of your mother in a herd of jostling adults, some weighing well over a ton, is dangerous for a small calf.

Walruses Can Learn New Sounds

One of the more surprising findings in walrus vocal research is that these animals can deliberately vary their sound production when motivated to do so. A study on Pacific walruses used a training approach where the animals were rewarded only for producing sounds they had not already made in a given session. The walruses responded by generating increasingly varied and novel sounds in air. When the same task was then tested underwater, with no additional training for the aquatic context, the walruses transferred the strategy, varying their underwater emissions until they hit something new enough to earn a reward.⁷

Many of the sounds and combinations the walruses produced during underwater testing were quite different from anything recorded during their baseline behavior or their in-air training sessions.⁷ This is not a trivial result. Vocal learning and vocal flexibility are relatively rare among mammals. Most mammal species produce a fixed set of calls determined largely by their anatomy and genes. The ability to generate novel sounds on demand, and to transfer that creative strategy from one medium (air) to another (water), puts walruses in a select group alongside cetaceans, bats, elephants, and a handful of other mammals with demonstrated vocal flexibility.

This flexibility also raises interesting questions about the breeding songs described earlier. If walruses can learn and modify their vocal output, then the stereotyped songs of breeding males may not be entirely hardwired. There could be a learned component, with young males acquiring song structure through exposure to adult singers. Researchers have not yet confirmed this in walruses the way it has been demonstrated in songbirds or humpback whales, but the underlying cognitive machinery for vocal learning is clearly present.

What Walruses Actually Hear

To understand why walruses produce the sounds they do, it helps to know what they can hear. An underwater audiogram of a Pacific walrus showed a hearing range with peak sensitivity at 12 kHz and a band of best hearing extending from 1 to 12 kHz.⁸ Below 1 kHz, sensitivity fell gradually. Above 12 kHz, it dropped sharply. The audiogram had the typical U-shape seen in most mammals, with one oddity: a peculiar dip in sensitivity around 2 kHz, even though the animal could hear 1.5 kHz and 3 kHz signals much better. The researchers attributed this to a narrow-band phenomenon specific to the tested individual, though whether it reflects something broader about walrus auditory anatomy remains unclear.

The practical takeaway is that walrus hearing is well tuned to exactly the frequency range their social calls occupy. The knocks, bells, and whistles of breeding males, and the barks of calves, fall squarely within the 1 to 12 kHz sweet spot. The relatively good sensitivity to low-frequency sound also means walruses are picking up environmental cues from waves, ice movement, and distant storms, which could help with navigation and habitat assessment. But that same low-frequency sensitivity creates a vulnerability.

When Boat Noise Drowns Out the Conversation

Walrus vocal behavior does not exist in a vacuum. Increasing vessel traffic in Arctic waters, driven by retreating sea ice and expanding shipping routes, is intruding on the acoustic space walruses depend on. A study monitoring walrus vocalizations in a proposed marine protected area found that vocalization rates dropped during and after vessel transits. The decrease was more pronounced around ships than around smaller motorboats, and rates were consistently highest before vessels arrived and lowest during and after encounters.⁹

This suppression effect matters because walrus calls are not background chatter. As the earlier sections make clear, these sounds carry specific social information: breeding fitness, individual identity, mother-calf bonding. When vessel noise causes walruses to go quiet, it is not just an annoyance. It potentially disrupts mate selection if singing males stop performing, weakens the mother-calf bond if recognition calls are suppressed, and alters social dynamics if rival males can no longer assess each other acoustically.

The walrus audiogram confirms the biological basis for this vulnerability. With strong sensitivity to low-frequency sound, walruses are tuned right into the frequency band where ship engines produce the most noise.⁸ The overlap between the noise profiles of vessels and the hearing range of walruses means that even vessels passing at a distance could be masking social signals. Whether walruses can compensate over time by shifting call frequencies, increasing call amplitude, or timing vocalizations around vessel passages is an open question. The documented vocal flexibility of the species suggests some adaptive capacity, but no one has shown that walruses actually deploy those compensatory strategies in wild settings under noise pressure.

Why Walrus Acoustics Are Hard to Study

One reason so many questions remain open is that walrus acoustic behavior is exceptionally difficult to study in the wild. The breeding season occurs during Arctic winter, when ice, darkness, cold, and rough seas make fieldwork dangerous and expensive. Most underwater recordings come from opportunistic deployments of hydrophones near known haul-out sites or from captive animals. Captive studies have been invaluable for documenting behaviors like flipper clapping and vocal learning, but captive environments are acoustically nothing like the open Arctic Ocean, and the social dynamics of a few animals in a pool cannot replicate the pressures of competing among hundreds of males in the wild.

Remote acoustic monitoring is improving the situation. Autonomous underwater recorders can be anchored in areas where walruses are known to gather, left for months, and retrieved later for analysis. This technology is how researchers documented the suppressive effect of vessel noise on walrus vocalizations, and it is also how call repertoires are being catalogued in locations that researchers cannot physically occupy during the breeding season. But automated recording generates enormous volumes of data, and distinguishing individual walrus calls from background noise, ice sounds, and other marine mammals requires either painstaking manual analysis or machine-learning tools that are still being refined for walrus-specific vocalizations.

The result is a field where major behavioral questions remain genuinely unresolved. Do different populations of walruses have distinct song dialects, the way some whale populations do? Do young males learn songs from older males, or is the song structure largely innate with individual embellishment? How far can a breeding male’s song propagate under realistic Arctic ice conditions, and does that propagation range match the spacing between competing males? These are questions the data should eventually answer, but the logistical barriers mean that progress comes in small increments, with each new hydrophone deployment or captive observation filling in one piece of a large puzzle.

Sounds That Are Not Vocal at All

It is worth noting that walruses also communicate through non-vocal sounds that sometimes get lumped into discussions of their “vocalizations.” The flipper clapping described earlier is one example: it produces sound, but through cavitation rather than the vocal tract. On land, walruses produce loud percussive sounds by striking their tusks against ice or rock, and the clacking of tusks during dominance disputes on haul-outs is a familiar sound to anyone who has watched walrus footage. These percussive and mechanical sounds are distinct from the tonal and pulsed calls of the underwater repertoire, but they serve overlapping social functions, particularly in establishing dominance hierarchies.

Even the sound of a walrus hauling its body onto ice conveys information to nearby animals. The splash and scrape of a large male climbing out of the water signals his size and vigor to others on the haul-out before any visual assessment takes place. In the perpetual twilight of the Arctic winter and the murky conditions underwater, acoustic information often reaches other walruses long before visual information does. The entire walrus social system, from breeding competition to maternal care to herd coordination, runs on sound to a degree that land-dwelling observers can easily underestimate.