Western South Atlantic Right Whale

Distribution

The three species of right whales are separated by ocean basins. While their calving and nursing grounds are generally located in shallow bays and nearshore waters on the continental shelf, all three species are thought to feed in productive offshore waters at high latitudes².  North Atlantic right whales are generally restricted to the coastal waters of the East coast of the United states and Canada, while southern right whales have a circumpolar distribution in the southern hemisphere roughly between the latitudes of 20° and 60° South.²

Southern right whales (E. australis) are native to the following countries and territories: Antarctica; Argentina; Australia;  Brazil; Chile; France ( Reunion, Southern Territories -Kerguelen); Gabon; Madagascar; Mauritius; Mozambique; Namibia; New Zealand; Peru;  South Africa; Uruguay

North Atlantic right whales (E. glacialis) are native to the following countries and territories: Bermuda; Canada; France (Saint Pierre and Miquelon), Greenland; Iceland; Ireland; Norway; Portugal (Mainland, Azores, and Madeira); Spain (Mainland and Canary Islands); United Kingdom; United States (East coast).

North Pacific right whales (E. japonica) are native to the following countries and territories: Japan; Russian Federation; United States (West coast).

Biology and Ecology

Feeding

Right whales feed almost exclusively on zooplankton, taking advantage of whatever species is abundant in their high latitude summer feeding grounds.  North Atlantic right whales predominantly feed on copepods (crustaceans approximately the size of a grain of rice)^2,3, while krill are likely to form a more important component of Southern right whale diets².  Right whales often skim feed at or just below the water surface, slowly swimming through clouds of plankton with their mouths half open and then straining the plankton through their long baleen plates.  But they can also feed at depth, and are known to surface with mud on their heads after a bout of bottom feeding².

Reproduction and growth

Right whales form large mating aggregations, which can include several males seeking access to a female.  However, unlike humpback whale competitive groups, male right whales do not engage in aggressive displays.  One female may successively mate with several males, and it is believed that males compete to pass their genes to the next generation through quantity of sperm they deliver when they mate, rather than fighting for access to females. This theory is supported by the fact that male right whales have the largest testes of any animal on earth (up to 500 kg each), as well as extremely large penises.   Mating has been observed year-round, but females give birth in the winter (December-March in North Atlantic right whales, and July – October in southern right whales) after a pregnancy lasting roughly 12 months².  Generally, females have one calf every three years, allowing a full year to gain strength and body condition after the demands of pregnancy and nursing².  A calf usually stays with its mother for the first year of life, during which it will double in body length⁴.  Calves appear to learn the locations of important feeding grounds by accompanying their mothers and returning to those sites for the rest of their lives.²

Research, threats and conservation status

Much of what we know about right whales today has been learned through photo-identification studies, in which individual whales are photographed and recognized over time by the unique patterns of the callosities on their heads.  Individual identification is now also often conducted through genetic sampling and matching of individuals.

The North Atlantic right whales that feed off the northeastern coast of the United States and the southern right whales off the Peninsula Valdes in Argentina are two of the best–studied populations, with accumulated data on several generations of whales^5,6. </p

In addition to individual identification studies, results from satellite telemetry (the attachment of small devices that send the whales’ GPS position and sometimes more detailed dive information) to satellite receivers) allow researchers to track whales’ movements and gain more insight into their (seasonal) migrations and fine-scale use of habitat on the breeding grounds and feeding grounds^7,8.  More information about research techniques used to study whales and dolphins can be found here.

Natural predators

There is no reliable information on natural predators of this species, although in the Southern Hemisphere, whales off the Peninsula Valdes in Argentina suffer potentially significant impacts from seagull attacks, which leave open wounds that can become infected¹³.

Human induced threats

The two most pervasive threats for endangered North Atlantic right whales are entanglement in fishing gear and ship strikes. More than 60% of North Atlantic right whales have scarring that indicates some interaction with fishing gear⁹. Some individual whales have carried rope and bits of gear on their bodies for months or years, eventually experiencing long slow deaths from infected wounds or lost feeding opportunities caused by the gear¹⁰.  Additionally, a number of North Atlantic right whales are killed each year from ship strikes as their feeding grounds overlap with major shipping lanes, particularly off the northeast coast of United States.¹¹  Recent regulations enforcing a reduction in vessel speed in areas of known right whale habitat may be helping to mitigate this threat¹² . 

Conservation status

Right whales were one of the first species of whale to be hunted, starting as early as the 11^th century¹⁴.  They were considered the ‘right’ whales to hunt, because they were slow, occur close to shore, float when dead, and yield large quantities of oil and baleen.  The species was hunted to the brink of extinction almost everywhere it occurred until it was protected under the first International Convention for the Regulation of Whaling in the 1930’s. 

North Pacific right whales have never recovered from this intensive whaling and are considered Endangered on the IUCN Redlist.  Sightings of the species are extremely rare, with almost nothing known of the species’ current distribution or numbers.  An abundance estimate for the Bering Sea and Aleutian Islands was only 31 individuals, with an estimated 8 breeding females¹⁵, while estimates generated for the migration route western north Pacific range between 416 and 1147. North Atlantic Right whales are also considered Endangered, with the western North Atlantic population currently estimated at roughly 500 individuals. There are only occasional sightings of right whales elsewhere in the North Atlantic. The population increased from 270 individuals in 1990, but is most likely in decline again since 2010¹⁶. There is particular concern about further decrease following an unusual mortality event with a high number of deaths in 2017.

Southern right whale populations breeding off the coasts of Argentina Uruguay and Brazil (southwestern Atlantic), Australia and South Africa have been  growing at rates of up to 7-8% per year since the cessation of hunting ^17,18.  As a consequence southern right whales are globally designated Least Concern on the IUCN Redlist, but sightings of animals of the southeastern Pacific population are rare and it is considered Critically Endangered. The southeastern Pacific and southwestern Atlantic populations are the subject of IWC Conservation Management Plans.

Right whales and whale watching

Please see the IWC Whalewatching Handbook