Southern Right Whale (E. australis)
Great right whale , baleine de biscaye (French)
Genus Eubalaena sp .
Time of appearance on Uruguayan coasts:
August to October (July season launch).
The southern right whale is one of the mammals which best adapts to aquatic life. Its robust, oval, large body lacks a dorsal fin and ventral folds (characteristic of the Balaenidae family). Its head is highly developed, measuring almost 1/3 of the total body length. The jaw is long and narrow and arches upward giving it its typical shape. The caudal fin is fibrous, without a bony skeleton and with powerful muscles. In adults, it can measure more than 5 meters.
The skin is smooth, elastic and dark grey in colour, with white spots on the belly of different shapes and sizes. There are very few calves that are born almost white, but as the animal becomes mature, it loses that hue until it reaches its characteristic colouration or a light grey colour.
Average lengths of adults: males = 14 meters. females = 16 mts.
Average adult weights: 45 - 60 tons
Newborns: lengths = 2 to 3 meters. weight approx. = 2 tons
In order to adapt to marine life, these animals have lost their hairy cover, although not completely. Nowadays we can find hairs (12 or 14 mm long) on the tip of the snout and also on the lower jaw. Their function is believed to be sensitive.
The southern right whale has two unique characteristics that differentiate it from other species of large whales:
- The first is their "V" shaped air exhalation mode, which can reach 4 meters of height. This figure is formed because it has two external respiratory holes or spiracles, located at the top and back of the head. These are divided by a cartilaginous septum and covered by two membranes with strong muscles, which hermetically close the holes when the animal is submerged, preventing the entry of water into the airways. This form of blowing is important because it allows the species to be identified at a great distance without the need to see them closely.
- The second characteristic that distinguishes the southern right whale is the presence of calluses, areas of thickened, elevated skin (approximately 5 cm thick) and of horny consistency, located in different parts of the head (Eye region, jaw, post-breather, lower lip edge and centre of the head).
The distribution, size and shape of these calluses vary from one whale to another and are not subject to change over time, so they are used to identify animals individually throughout their lives (comparable to the fingerprints of human beings). The calluses, which develop in the fetal stage, are dark grey in colour, but are covered by dense populations of small amphipod crustaceans called Cyamids (hosts of non-parasitic whales) and sometimes Cirripediums (dog teeth) can be found as well, which make calluses appear white (characteristic colour), yellow, orange, or light pink. The general distribution of calluses occurs along the upper margin of the lower lip, jaw, the dorsal surface of the face and over the eyes. The most important and biggest callus is the "bonnet", which is located at the tip of the snout.
Popular belief assumes that whales expel a jet of water - it appears on the coat of arms of the Maldonado department. But in reality, it is a vapour cloud that arises as a consequence of the expiration in order to empty the lungs. The humid exhaled air condenses the surrounding water vapour by cooling it. Normally whales breathe five or six times per minute before diving again, and this frequency is related to its activity at that time. The columns of steam or snorts reach 8 meters in height in the sperm whale, the blue and the fin whale. The ancient sailors advised against coming into contact with the puff, as according to them it was pungent and caused irritation and skin burns. Some claimed that its smell was so unbearable, it produced brain disorders.
When the polar summer begins, as a consequence of light and accumulated nutrients, the massive "flowering" of small algae occurs. Zooplankton grows at their expense and consequently large migratory whales appear, thus one of the longest migrations in the animal kingdom starts. This tradition is surely an interesting paradox of nature: the largest animals in creation eat microscopic animals.
Different feeding strategies and preferences make it so that the feeding territories do not overlap between the whales. Usually, they go from their summer feeding polar territories - in high latitudes - to the winter-growing tropical areas - in low latitudes.
They feed in cold waters (high latitudes 60 °) during the summer, migrating in winter to warm waters, (medium and low latitudes) with the aim of breeding, presenting coastal habits during this period.
The krill banks, especially copepods, are their main food. They feed by furrowing the surface water, with their mouths ajar, so they "strain" the zooplankton in a method called "foaming". This feeding system does not force them to dilate the throat and therefore they do not have ventral grooves or gular folds like all fin whales. They eat up to 300 kg in 1 hour up to 1 ton per day.
At the end of the summer, they leave the feeding areas of the colder high latitudes and look for coastal regions where they concentrate for mating, calving, and lactation of offspring born in the year following fertilization. From June to November, the southern right whale searches for bays for these purposes, located between 20 and 30 º South.
Courtship and mating:
Regarding the reproductive social behaviours, only two species of mysticetes have been well studied: those of jubarta and the right whale. Both form a group during the winter, in different areas, competing for access to the females through sounds and fights. With "harem" breeding systems, only a few males have the opportunity to mate with the receptive females. Courtship and wedding stop, contrary to what is imaginable, and do not always include a successive series of complex acts and sounds, emitted by mature males (structured and cyclical sounds, "whale songs"). As part of ritual acts, courtships, chases, caresses, rubs and jumps happen.
The elusive behaviour of females has a precautionary component: to avoid breeding with the wrong male. While the paternal responsibility ends with fertilization, the maternal continues with great effort for 2 years (in most whales, killer whales and sperm whales), therefore this high-cost investment for the female must be compensated with healthy offspring. Young calves that are born sick or with little chance of survival are abandoned. The mother's prenatal investment in blue whales is impressive. In the last two months of pregnancy, the fetus increases its weight by 100 kg daily, and babies are born weighing 3000 kg.
Often, mothers take their time to recover for a full year. So the recovery of this threatened species becomes very slow.
Regarding the weight of the southern right whale hatchlings, it should be noted that it is identical to that of the blue whale calves, whose adult measures twice (32 meters + -) than the southern right whale (16 meters + -).
Despite not being able to differentiate a male from a female with the naked eye, without the need to see the animal's belly, there is a marked sexual dimorphism: Females are larger than males. In males, calluses are more numerous and larger than in females. The male genital cleft is more than twice the length of the female genital cleft. It has an inverted "Y" shape, it is separated from the anus and ends near the navel. In females, the genital cleft is located starting on the anus, it is separated from the navel, and on each side of it, the mammary grooves are present.
Gestation and birth: (for cetaceans in general)
The prenatal development of cetaceans is similar to that of other mammals. While in most mysticetes the gestation or pregnancy lasts between 10 and 12 months, in the odontocetes it is more variable, ranging from 9 to 18 months. These differences are probably related to seasonal feeding migrations in mysticetes. In the births observed so far, the young calves begin to emerge “from the tail”, contrary to most of the land mammals that come out with their heads first. Breaking the umbilical cord is fast so that the newborn takes his first breath. Usually, a single individual is born; multiple births are abnormal. Breastfeeding lasts between 11 and 14 months in mysticetes, in odontocetes it can last for more than 1 year. Most fin whales do not copulate until the end of lactation and stop once every two years.
The milk squirts into the baby's mouth. Due to its high-fat content, it is insoluble in water and on contact forms - "milk bubbles" that the young take advantage of.
It has been calculated that young blue whales nurse about 380 litres of milk a day and gain 900 kg a day for seven months. Their mothers produce about 600 litres a day. The maternal behaviour of entire groups increases the probability of survival. They are matriarchal groups analogous to African elephants.
How long do they live?
The longevity of the right whale is still unknown, but a whale was once found with a 250-year-old harpoon stabbed into its body, which was dated by radioactive carbon.
It lives in the waters of the South Atlantic, South Pacific and Indian Oceans, restricting its area between 20º and 60º latitude. Every year about 600 animals flock to Peninsula Valdés, Argentina, the most important habitat of the Southwest Atlantic. The rest occupy other important areas such as Santa Catarina, Brazil, Tristan da Cunha and South Africa.