For a long time, the orca gets cloaked in an aura of terror. Now we know best its reputation as a ruthless assassin. The exaggerated tales of whales has given way to admiration. Yet many aspects of its life remain unknown.
The family of dolphins appeared in the Miocene, about 11 or 12 million years ago. The orca is the largest of all dolphins. Some fossils of the species were in Italy (Tuscany) and England (Suffolk). They were from the Pliocene land (1.5 million years ago). The bone remains of orca, date back to prehistoric times in northern Europe.
Most of these lives in groups, which sometimes go aground in mass on the coast.
Orca is also called killer whale, murderer, and assassin. It is the most powerful and fearsome predator of the animal world. The orca is the only cetacean that assaults other marine mammals, even the greatest. To feed themselves, they can also kill a whale or another dolphin. For this reason, it earned the English name Killer Whale.
Its diet is in fact very varied. The horrific predator turned out to be easy to train. It manifests similar behaviors to those of smaller dolphins. With which even manages to cohabit. Its bad reputation has thus given way to a feeling of affectionate admiration.
A quiet community and united family
Lovers of community life, killer whales travel in small herds of 5-20, near the coast. The typical herd is a slight majority of adults than young. Among adults, the number of females is higher than that of males. This explains the higher mortality rate in males.
Each pack is likely a family linked by very strong relationships. It has its own vocal repertoire, which allows you to identify it. While, being very stable, the group can split for a few hours, in particular when the animals are in search of food. You can then see them swim alone in small distance of several kilometers one from the other subgroups.
The stability of the group is not absolute. Some may choose to lead a solitary life. Family groups are generally independent of each other. Although several groups can also play together in community.
In a typical day, Orca devotes half of its time to search for food and to catch prey. Meetings with other groups take up all the remaining time. According to a certain order the rest, generally, follows the hunting. The games, in turn, precede the displacements. The life thus is splendid and organized. It has extreme intelligence, punctuated by very precise rhythms and rules.
Surprising agility and noisy
Killer whales often adopt attitudes of observation. Rising to the surface, they raise for a moment his head out of the water. Or stand on end, sometimes emerging to the level of the pectoral fins. As if to make a tour of the horizon of the surrounding space.
Such observation positions, such as spy hopping, can sometimes be simultaneous. They are common in young people, who thus reveal their curiosity. Equipped with an excellent view, the orcas manage to find such a possible prey on the shore.
Often when playing with her companions, the orca beat the water with their fins. The noise of quick shots settles which, given the shape of the fin, are very like the slaps on the sea surface. The pectoral fins beating with the caudal fin spreads under water.
These same behaviors are also observed during the early stages of mating. During the hunt, they mean to frighten and disorient the fish. This spectacular play is always noisy and lively. The orca shows a certain flexibility despite the bulk and weight. Raising its tail out of the water, it swings from right to left. Or makes surprising leaps emerging almost completely.
Like the other dolphins, killer whales like to brush against each other. Individual contacts are rather short. But, these animals as in the Strait of Puget love to spend a lot more time, sometimes even an hour in a row. They rub against the bottom of stones, in special places chosen for this purpose. Killer whales cannot resist the temptation to rub against algae. They bring back to the surface some to better feel the caress on the tail fin. It is not known whether this is a game, a pleasure or a necessity.
A ruthless and intelligent slayer
Killer whales, like other dolphins, almost always in the hunt group. Research and capture prey involve the cooperation of all the animals. The hunting techniques and group size adapt to the nature of prey.
Coordinating the research, identification of schools of fish is much easier. Killer whales disperse over an area of two kilometers and swim at a speed of 5 km/h approx. They may as well explore the sonar 10 square kilometers per hour.
The echolocation signals allow each to sense its position in relation to others. They stay in touch in the general group strategy. These signals are not enough, to coordinate the actions of the group as a whole. In particular, when it is necessary to gather a shoal of fish, Orca uses the beeps.
The signals are specific to the group, and represent a kind of dialect. The researchers noted similarities in their dialects of various groups. Finally, each can emit a specific sound, comparable to the timbre of the human voice. This signature allows animals to recognize and, for some of them, to direct the operations.
They also know the places where whales, seals or sea lions use to focus at certain times of the year to breed.
The capture of those coveted prey and putting them to death depend on the size and the number of future victims. The whales, which usually move alone or in small groups are difficult opponents. To catch a prey, many killer whales coalesces. If you are in the coastal area, their only chance of salvation is to take refuge in the shallow waters near the shore. Here they are less attackable.
On the open sea, seals and sea lions are easy prey. But when you are near the coast or ice, they can escape their predators (if they have identified them in time). For marine mammals the most effective method to escape a pack of killer whales is to reach a school of fish. In fact, if the fish is abundant, whale, sea lions and seals can approach the orcas without fear.
An affectionate baby every three years
When it begins the season of love, the approach between male and female begins almost like a game. Between flips and various caresses, the partner rub and roll against one another. After these preliminary steps, the coupling occurs at the surface. There is a large amount of water splashes and vortices. The actual act is very short and lasts up to 30 seconds. The animals mate in horizontal or vertical position, belly to belly, holding tight with the fins.
The duration of gestation is 15 to 16 months. The females give birth to a single pup, no more than once every three years. Childbirth and the treatment of the little ones are not different from that of dolphins. The mother, helped by another female, pushes the newborn to the surface to allow it to breathe.
At birth, the little orca measure from 2.20 to 2.90 meters, but it grows fast. The first year it seems that they only feed on breast milk and that will never turn away from the mother.
Sometimes you encounter subgroups of orcas composed only of infants and young. In reality, they are not alone. There is always an adult nearby and its function is to watch. And, in some circumstances, also coordinate activities.
As in all cetaceans, the Orca growth occurs very fast during the first years of life. Then a decade, that of females slows, while males continue to grow. In adulthood, they can reach a length of almost 10 meters, while females do not exceed 7 meters. To this difference in size also is usually a weight difference. Adult males weigh sometimes double of females (8:4 tons).
The Orca longevity is approximately 35 years. In nature, the orca has little to fear. Apart from humans and other killer whales, its enemies are few. Yet they are so tough that stand up well to the harpoons.
The three white patches that adorn the belly and the orca back are characteristic of the species. On the back, a crescent stain is a bit like a saddle behind the dorsal fin. There is another on the head, above the eye and set back from that, it has an oblong shape. The most important spot starts from the lower jaw. It occupies the entire ventral surface and takes the form of a trident.
The fifty teeth allow the animal to hold and tear prey of large size.
The skeleton of the fin comprises the same bony elements of the forelimbs of mammals. The humerus, radius and ulna are particularly short. The last two are much flattened above and below. Only the joint between the humerus and the scapula is mobile. The others are sinartrosate or fixed.