Walruses mate in the water during the Arctic winter, primarily in January and February, while gathered around openings in the pack ice. The process involves elaborate underwater singing by males, physical competition for access to females, and a mating system where dominant bulls guard and breed with groups of females over periods of days at a time.
When and Where Breeding Happens
Walrus breeding is tightly tied to the Arctic ice pack. In the Pacific population, several thousand adult males spend much of the year separated from females in the Bristol Bay area of Alaska. Come fall, these bulls migrate northward to the St. Lawrence Island region, where they rejoin the larger herd wintering along the edge of the sea ice in the Bering Sea. Mating takes place in January and February at polynyas, which are areas of open water surrounded by ice where walruses haul out and feed.
Atlantic walruses follow a similar pattern in the Canadian High Arctic, congregating around polynyas during the breeding months. These ice-edge gatherings provide both the social density needed for mating and access to the water where most courtship and copulation occur.
How Males Compete for Females
The walrus mating system is best described as female-defense polygyny. A single large, mature male gains exclusive access to a herd containing several females and defends that position for one to five days at a stretch. During that window, he is the only male that participates in breeding activities. Other sexually mature males are present in the herd but take on subordinate roles, either staying silent among the group or hovering nearby as vocal satellites.
Tusks play a central role in sorting out which males get access. When two males encounter each other, they raise and turn their heads sideways to display their tusks. If one male’s tusks are clearly smaller, he typically backs off without a fight. When the tusks are similar in size, the confrontation escalates into stabbing and wrestling that can leave both animals with bruises and puncture wounds. The result is a dominance hierarchy where the largest, most heavily tusked males monopolize breeding opportunities.
Males that can’t claim a herd employ alternative strategies. Some remain as silent members of the group, blending in without challenging the attending male. Others position themselves as vocal satellites nearby, singing fragments of their own songs in sporadic bursts. Some alternate between both roles, presumably waiting for an opportunity if the dominant male tires or moves on.
Underwater Songs and Courtship
The most distinctive feature of walrus mating is the male’s underwater song. While attending a herd, a dominant male continuously repeats a complex, stereotyped vocal sequence that can last for hours or even days without significant interruption. These songs consist of hundreds of short, repetitive pulses delivered in cycling patterns, and they include rhythmic knock sequences punctuated by metallic, bell-like sounds.
The knocks are low-frequency pulses with most of their energy between 500 and 2,000 Hz, repeated at a steady rhythm of roughly one per second. Males also produce intense clapping sounds created by a physical mechanism called cavitation, where rapid movement of body parts in water generates powerful pressure waves. The regularity and intensity of these claps likely signal a male’s fitness to both rivals and potential mates.
A female most likely mates with whichever male is attending the herd when she becomes receptive. Physical courtship behaviors between males and females include grabs, rolls, and holds in the water, sometimes paired with tusk contact or nuzzling. Observations of captive walruses suggest males may show preference for certain females, with some pairings involving more frequent and sustained interaction than others.
Pregnancy and Calving
After mating in January or February, the fertilized egg does not immediately implant in the uterus. This strategy, called delayed implantation, means the embryo essentially pauses development for about four months. Active fetal growth begins around mid-June, and calves are born the following spring, in late April or May, during the northward migration. The total time from mating to birth is roughly 15 months, though only about 11 of those involve active development.
Calves are born on the sea ice, where mothers nurse and protect them. Because raising a calf demands so much energy, females typically produce only one calf every three years. This slow reproductive rate makes walrus populations vulnerable to disruption, since losses are difficult to replace quickly.
Age and Readiness to Breed
Female walruses reach sexual maturity and begin cycling earlier than males, with estrus occurring primarily between February and June, peaking in March. Males, while they may become physically capable of breeding at a younger age, rarely get the chance to mate until they are large and dominant enough to claim a herd. The social structure means that even young adult males with full reproductive capacity spend years as silent herd members or vocal satellites before they can compete with the biggest bulls. This creates a significant gap between biological maturity and actual reproductive success in males, a gap that can span several years depending on the individual’s size and fighting ability.
How Sea Ice Loss Affects Mating
Walrus reproduction depends on stable pack ice for hauling out, giving birth, and nursing. In recent years, ice-free summers in the Chukchi Sea have forced walruses to haul out on shore instead, creating massive, crowded gatherings on beaches. While mating itself occurs during the winter ice season, the broader disruption to walrus habitat and migration patterns has raised concerns about long-term reproductive success. With females already producing a calf only once every three years, any additional pressure on survival or breeding conditions compounds slowly but significantly across generations.