Southern right whales (Eubalaena australis) are among the largest animals in the Southern Hemisphere, reaching lengths of roughly 15 to 17 meters and weighing up to 80 tonnes. Once hunted to the edge of extinction, the species has become one of conservation biology’s qualified success stories, with most populations growing steadily since international protection began in the mid-twentieth century. Their recovery, though, is uneven across ocean basins and increasingly shaped by forces that have nothing to do with harpoons.
Recognizing a Southern Right Whale
If you see a large, dark whale with no dorsal fin cruising close to shore in the Southern Hemisphere’s winter, there is a good chance you are looking at a southern right whale. The most distinctive feature is the pattern of raised, roughened skin patches on the head called callosities. These patches stay gray throughout the animal’s life, but they look white, yellow, or orange because of dense colonies of whale lice (cyamids) living on them.1Encyclopedia of Marine Mammals. Callosities The callosity pattern is unique to each individual, which makes it invaluable for researchers tracking whales across years and decades using photo-identification.
Males tend to have more callosity coverage on their heads than females, and the patches appear to serve a purpose during mating competition. Observers have documented males deliberately scraping the tops of their heads along the backs of rival males, with the scraped whale twisting and writhing in response.2Encyclopedia of Marine Mammals. Callosities Beyond the callosities, the species has a broad, arched mouth, a rotund body, and paddle-shaped pectoral fins. The combination of no dorsal fin and a V-shaped blow from two widely spaced blowholes makes identification at a distance fairly straightforward.
From Near-Extinction to Cautious Recovery
Southern right whales got their name from being the “right” whale to kill: they swim slowly, float when dead, and yield enormous quantities of oil and baleen. Commercial whaling hammered them from the nineteenth century onward, pushing some regional populations to the brink. In New Zealand waters, for example, a pre-exploitation population estimated at roughly 29,000 to 47,000 animals was reduced to about 30 to 40 mature females between 1914 and 1926. Today that population remains below 12 percent of its original size.3PubMed Central. An integrated approach to historical population assessment of the great whales: case of the New Zealand southern right whale Across the Southern Hemisphere more broadly, reliable assessments of how mass depletion affected baleen whale populations remain incomplete, but the scale of the damage is clear.4Fish and Fisheries. Ecosystem modelling to quantify the impact of historical whaling on Southern Hemisphere baleen whales
Genomic evidence adds another layer to the story. Deep whole-genome sequencing of North Atlantic right whales and Southwest Atlantic southern right whales shows that the two species had already diverged in effective population size well before modern whaling began, with southern right whales historically maintaining larger populations. Whaling then drove declines in both, but the North Atlantic species had far less genetic diversity to absorb the blow.5PubMed Central. A comparison of genomic diversity and demographic history of the North Atlantic and Southwest Atlantic southern right whales That genetic head start helps explain why southern right whales have rebounded while North Atlantic right whales remain critically endangered and declining.6Diseases of Aquatic Organisms. Assessing North Atlantic right whale health: threats, and development of tools critical for conservation of the species
How Fast Are Populations Growing?
Recovery rates vary dramatically depending on which ocean basin and which coastline you look at. In southeastern Australia, the population comprises an estimated 268 individuals with 68 breeding females, growing at about 4.7 percent per year between 1996 and 2017. Despite that growth rate, the number of mother-calf pairs showing up at the sole known calving ground at Logans Beach in Victoria has not increased significantly over three decades.7Endangered Species Research. Population estimate and rate of increase of southern right whales Eubalaena australis in southeastern Australia
In South Australia, the picture is more dynamic. At the major aggregation area of Head of Bight, annual growth has moderated to about 3.3 percent per year, but at Fowlers Bay, where whales are recolonizing, growth rates are far higher, around 15 percent per year.8Marine Mammal Science. Decadal Shifts in Southern Right Whale (Eubalaena australis) Recovery in South Australian Waters: Implications for Conservation and Management That pattern suggests whales are spreading into previously abandoned habitat as core sites reach some kind of social or ecological capacity. Recovery, in other words, is not just a matter of numbers going up. It involves whales reclaiming stretches of coastline they haven’t used in over a century.
Where They Go and Why They Come Back
Southern right whales follow a broadly predictable annual cycle: they feed in cold, productive waters at high latitudes during summer and migrate to sheltered coastal bays in temperate and subtropical regions to breed and calve during winter. Satellite tracking of tagged individuals shows just how far these migrations stretch. Whales tagged at Australia’s Head of Bight and at New Zealand’s Auckland Islands traveled southwest toward the Southern Ocean after departing their winter grounds, with one sub-adult from Tasmania reaching as far south as 65°S before turning back.9PLOS ONE. Satellite derived offshore migratory movements of southern right whales (Eubalaena australis) from Australian and New Zealand wintering grounds Daily distances ranged from 20 to 61 kilometers, depending on the individual. The paths were far from straight lines, suggesting the whales follow shifting prey patches rather than fixed corridors.
Females show strong fidelity to specific calving sites. Three decades of photo-identification data at Head of Bight found that about 77 percent of known females returned there to calve.10Journal of Cetacean Research and Management. Southern right whale residency, site fidelity and calving parameters at the Head of Bight, South Australia Some individuals were photographed with a calf at the same site up to 13 times over the study period. That fidelity extends across generations: 24 calves born at Head of Bight were later documented returning there as adults, with resighting rates climbing sharply after six years, roughly the age of sexual maturity.
Yet the same dataset reveals a decline in site fidelity over time. In the early 1990s, about 92 percent of reproductive females returned to Head of Bight between years, compared with roughly 58 percent across the full study period.11Journal of Cetacean Research and Management. Southern right whale residency, site fidelity and calving parameters at the Head of Bight, South Australia Mean residency at the site has also dropped, from 71 days down to 53 days for mothers with calves. This dovetails with the recolonization of sites like Fowlers Bay: as the population grows, whales appear to be distributing themselves more widely rather than packing into one bay.
What Southern Right Whales Eat
Southern right whales are filter feeders, swimming with their mouths open to strain zooplankton through their baleen plates. In the Southern Ocean during summer, krill is a primary food source. But they also feed opportunistically during winter, which was not always appreciated. In Golfo Nuevo off Argentina’s Península Valdés, researchers documented whales making foraging dives to reach dense aggregations of large calanoid copepods and euphausiids concentrated in deeper water.12Scientific Reports. Foraging dives of southern right whales (Eubalaena australis) in relation to larger zooplankton size prey availability in Golfo Nuevo, Península Valdés, Argentina The whales targeted the larger life stages of these tiny crustaceans, suggesting they are selective about prey size even among organisms barely visible to the naked eye.
This reliance on zooplankton makes southern right whales vulnerable to anything that disrupts plankton production, and that vulnerability connects directly to climate.
Climate, Krill, and Breeding Success
The link between climate conditions and southern right whale reproduction is one of the most striking findings in the recent literature. In the South Atlantic, calving success correlates strongly with krill density and with large-scale climate indices. Research on the population that calves off southern Brazil found significant correlations between the number of calves born and krill densities, El Niño conditions (with a six-year lag), Antarctic Oscillation, and Antarctic sea ice area.13PubMed Central. Southern Right Whale (Eubalaena australis) Reproductive Success is Influenced by Krill (Euphausia superba) Density and Climate The six-year lag with El Niño is not a coincidence: it roughly matches the time between a female feeding heavily in preparation for pregnancy and the resulting calf being counted on the breeding grounds. Poor feeding conditions years earlier mean fewer calves years later.
Studies of the Argentine population at Península Valdés have found parallel patterns, with calving output tracking sea surface temperature anomalies near South Georgia, a major krill habitat, in the preceding autumn.14PubMed Central. Global climate drives southern right whale (Eubalaena australis) population dynamics More recently, broader analyses have linked warmer, less productive conditions at mid-latitude foraging areas and reduced sea ice coverage to longer calving intervals, meaning females wait longer between pregnancies when feeding conditions are poor.15Scientific Reports. Climate-driven reproductive decline in Southern right whales If climate change reduces the frequency of high-krill years, the recovery that looked so promising could slow or stall.
Kelp Gulls and a Unique Form of Harassment
One of the strangest threats to southern right whales does not come from the ocean at all. At Península Valdés, Argentina, kelp gulls have learned to land on the backs of resting whales and peck through their skin and blubber to feed on the tissue underneath. This behavior has been documented since the 1970s, and it has intensified over the decades. The wounds are sometimes large enough to see from shore.
The impact goes well beyond the physical injuries. Even when no gulls are actively attacking, whales at Península Valdés breathe at much higher rates than southern right whales in Australia: mothers show roughly 50 percent higher respiration rates and calves about 25 percent higher. During active attacks, calf breathing rates jump another 10 percent. Mothers frequently adopt irregular breathing postures, working against their natural buoyancy, which burns extra energy.16Marine Ecology Progress Series. Acute and chronic behavioral effects of kelp gull micropredation on southern right whale mother-calf pairs off Península Valdés, Argentina Calves at Península Valdés spend less time nursing during each bout compared to calves in Australia, though they attempt to suckle more frequently, suggesting their feeding is being chronically disrupted.
The gulls also appear to target calves that are already wounded, compounding the damage. These chronic and acute behavioral disruptions carry energetic costs that could affect calf survival and, eventually, population-level reproductive success.17PubMed Central. Effect of kelp gull harassment on southern right whale calf survival: a long-term capture-recapture analysis The situation at Península Valdés is essentially unique to that region. Southern right whales elsewhere do not face this kind of sustained aerial harassment, which makes it a localized but serious conservation concern for one of the largest known breeding aggregations.
Ship Noise and Chronic Stress
Underwater noise from commercial shipping is a problem for all baleen whales, but a natural experiment following the September 11, 2001, attacks provided unusually clear evidence of its effects. When shipping traffic dropped in the Bay of Fundy, Canada, underwater noise fell by 6 decibels, with the most significant reduction below 150 Hz, exactly the frequency range where large ships are loudest and baleen whales communicate. That noise reduction was associated with a measurable decrease in stress-related hormone levels in North Atlantic right whales’ fecal samples.18PubMed Central. Evidence that ship noise increases stress in right whales
That study was conducted on North Atlantic right whales rather than their southern cousins, but the implications extend to any right whale population living in or migrating through heavy shipping lanes. The finding was the first direct evidence linking low-frequency ship noise to chronic physiological stress in whales, not just behavioral avoidance. For southern right whales, whose calving bays in South Africa, Argentina, and southern Australia overlap with busy coastal shipping routes, the relevance is hard to ignore.
Mating by Committee
Southern right whales have a mating system that is unusual even among large whales. Females mate with multiple males during a breeding season, and males mate with multiple females, a strategy known as polygynandry. Rather than fighting for exclusive access to a female, males compete through sperm quantity. Right whales have the largest testes relative to body size of any whale, reflecting the intensity of this sperm competition.19Sex in Cetaceans. Right Whale Sexual Strategies and Behavior
Mating takes place in surface active groups, where two or more whales jostle at the surface with frequent physical contact. A single female may be attended by a dozen or more males. These groups are conspicuous, noisy, and sometimes last for hours. The female often rolls belly-up at the surface, which effectively prevents mating until she rolls back, suggesting that females exert some choice over which males eventually copulate. The large callosities on males’ heads may serve as tools during the pushing and shoving within these groups, consistent with the scraping behavior researchers have observed.
The Role Whales Play in the Ocean
Southern right whales are not just passengers in the Southern Ocean ecosystem. They are active participants in nutrient cycling. By feeding on krill at depth and defecating iron-rich feces near the surface, whales effectively pump limiting trace elements from the lower water column into the zone where phytoplankton can use them. Krill themselves help retain trace elements in surface waters because they are long-lived and actively swim, but whales concentrate certain elements through their physiology and then redistribute others through their waste.20PLOS ONE. The Biogeochemical Role of Baleen Whales and Krill in Southern Ocean Nutrient Cycling
This means that the historical removal of hundreds of thousands of great whales through industrial whaling did not just reduce whale numbers. It likely altered the productivity of the Southern Ocean itself by disrupting the nutrient recycling loop between krill, whales, phytoplankton, and the atmosphere. As whale populations recover, restoring this ecological function is an underappreciated benefit.
Whale Watching and the Question of Disturbance
Southern right whales are a major draw for whale-watching tourism, particularly at Península Valdés in Argentina, Hermanus in South Africa, and several bays along Australia’s southern coastline. The whales’ habit of calving in shallow, sheltered water close to shore makes them unusually accessible. But that proximity raises questions about whether boats disturb the animals.
Research in Patagonia found that whales responded differently depending on how boats approached. When vessels approached with engines off, whales reacted positively, sometimes approaching the boat and seeking contact. When boats came in with engines running, whales moved away and avoided contact.21Tourism Management Perspectives. Impact of whale-watching on the short-term behavior of Southern right whales (Eubalaena australis) in Patagonia, Argentina In South Australia’s Encounter Bay, researchers documented a significant drop in resting behavior after whale-watching interactions: mothers went from resting about 62 percent of the time during control periods to just 30 percent afterward, while calves dropped from 16 percent to barely 1 percent.22Marine Policy. Effects of whale-watching activities on southern right whales in Encounter Bay, South Australia
These disruptions may seem minor in isolation, but for a lactating mother already expending enormous energy to nurse a growing calf, repeated disturbances over a calving season can add up. Regulations governing approach distances, engine use, and time spent near whales exist in most jurisdictions where whale watching occurs, but enforcement varies widely. The Argentine research suggests that how boats behave matters at least as much as how close they get.
Conservation Across Borders
Southern right whales do not respect national boundaries. A whale that calves off Argentina may feed near South Georgia, which falls under British jurisdiction, and pass through the territorial waters of Uruguay and Brazil along the way. This creates a governance challenge. A recent analysis of marine protected area networks in the western South Atlantic found that cooperation for the conservation of southern right whales is limited to within-country networks, with no meaningful transboundary collaboration.23PubMed. Networks of interactions between Marine Protected Areas and their effects on the conservation of the South American sea lion and the Southern right whale in the Western South Atlantic Ocean The networks that exist have low density, meaning the protected areas along a whale’s migratory route are managed independently rather than as parts of a connected system.
This gap matters most for threats that are diffuse and cumulative: shipping noise, fisheries entanglement, and pollution do not concentrate neatly inside one country’s marine park. A whale protected in its calving bay may spend the rest of the year in waters where no protections apply. Strengthening international coordination has been identified as essential for the long-term conservation of migratory marine species like southern right whales, but translating that recognition into functional agreements between countries with different economic priorities and institutional capacities remains slow work.
Colonial History and Indigenous Relationships
Southern right whales shaped human cultures long before industrial whaling. In Australia and New Zealand, Aboriginal and Māori communities had deep relationships with the species that predated European arrival. Research into the cross-cultural histories of bay whale fisheries in the early nineteenth-century Tasman region suggests that the changing behaviors and distributions of right whales themselves influenced how Indigenous communities participated in the emerging colonial whaling industry.24Environment and History. A Whale of a Difference: Southern Right Whale Culture and the Tasman World’s Living Terrain of Encounter In this reading, the whales were not just passive resources but agents whose own cultural patterns, including migration routes and site fidelity, shaped the encounters between Indigenous peoples and colonial newcomers.
Today, southern right whales hold cultural significance for coastal communities around the Southern Hemisphere, from the annual whale festival at Hermanus in South Africa to the recognition of Península Valdés as a UNESCO World Heritage Site partly because of its right whale population. For many of these places, the whale is simultaneously a symbol of ecological recovery, a tourist attraction, and a reminder of how quickly a species can be brought to the edge of disappearing.