For a long time, the orca has been cloaked in an aura of terror. Now that we know best, however, its reputation as a ruthless assassin, the exaggerated tales of whales, has given way to admiration. Yet many aspects of its life remain to be discovered.
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 found in Italy (Tuscany) and England (Suffolk) from the Pliocene land (1.5 million years ago), and bone remains of orca, dating back to prehistoric times, which have been found in northern Europe.
Whale with teeth, or odontocete, like all the dolphins, porpoises, sperm whales and beaked whales, was sometimes classified as a separate subfamily along with some other dolphins such as the pilot whale, the false killer whale and dolphin Risso. Most of these lives in groups, which sometimes go aground in mass on the coast.
Also called killer whale, murderer and assassin, and known as 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 slay a whale or another dolphin. For this reason the whalers, with their stories, are the source of its reputation as ravenous hunter, which earned precisely the English name Killer Whale.
Its diet is in fact very varied. Since, it was possible to observe the different dolphinariums around the world, the horrific predator turned out to be easy to train, manifesting similar behaviors to those of smaller dolphins, with which even manages to cohabit. Its bad reputation has therefore 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, mostly near the coast. According to observations made in the area of ??Vancouver (Canada), the typical herd is formed by a slight majority of adults (57%) than young (43%), where about 4% is still breast-fed. Among adults, the number of females are higher than that of males, which is probably explained by a higher mortality rate in males.
Each pack is likely a family linked by very strong relationships, which has its own vocal repertoire, which allows you to identify it. While, however, being very stable, the group can be 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, however, and some individuals 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; 27% to the movements; 13% to the game and sexual activity; 12% to rest and sleep. Meetings with other groups take up all the remaining time, equal to 2%. These activities are carried out in sequence. According to a certain order the rest, generally, follows the hunting and can be followed by the games, which, in turn, precede the displacements. The have a life, therefore, that is splendid, organized and conducted with extreme intelligence, punctuated by very precise rhythms and rules.
Surprising agility and noisy
The jumps, dives and spectacular movements of what the killer whales do not seem related to swimming or movement. 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 vertically, sometimes emerging to the level of the pectoral fins, as if to make a tour of the horizon on the surrounding space.
Such observation positions, such as spyhopping, can sometimes be taken simultaneously from different animals of the same group and are common in young people, who thus reveal their curiosity. Equipped with an excellent view, the orcas probably manage to find such a possible prey on the shore and find a way out when you are surrounded by boats.
Often when playing with her companions, the orca violently beating the water with their fins. The noise of quick shots settling (which, given the shape of the fin, are very similar to the slaps) on the sea surface with the pectoral fins or beating rhythmically with the caudal fin spreads rapidly under water, and it is so strong that it can also be heard several kilometers away.
These same behaviors are also observed during the early stages of mating. During the hunt, however, they probably meant to frighten and disorient the fish. Even during his spectacular play, always noisy and lively, the orca and demonstrated a certain flexibility despite the bulk and weight. Raising its tail out of the water, the long swings from right to left, or makes surprising leaps emerging almost completely. Then dives head down or you let fall heavily on the belly, on the back or side, raising such a large amount of water spray to seem immersed in a white cloud.
Like the other dolphins, killer whales like to brush against each other. Individual contacts are rather short; on the contrary, these animals - as has been observed in the Strait of Puget - love to spend a lot more time, sometimes even an hour in a row, rubbing against the bottom of stones, in special places chosen for this purpose. Finally, when passing near a field of algae, killer whales do not resist the temptation to rub against those plant and 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 are adapted to the nature of prey: fish shoals of all kinds (Argentine fish and cod) or marine mammals, large and small.
Coordinating the research, identification of schools of fish is much easier. Killer whales are dispersed 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, large surface area compared to what could scour isolated orca or a compact group.
The echolocation signals emitted and received by the various individuals allow each animal to sense its position in relation to others, to stay in touch with them and to participate in the general group strategy. These signals are not enough, however, to accurately coordinate the actions of the group as a whole, in particular when it is necessary to gather a shoal of fish; Orca uses then beeps.
Resident killer whales in the Strait of Puget populations, it was possible to distinguish forty different signals, some of which are specific to the group, and represent a kind of dialect. The researchers noted similarities in their dialects of various groups, and the similarities, allowing to assess the degree of familiarity existing between these groups. Finally, each individual can emit a specific sound, comparable to the timbre of the human voice. This signature allows animals to recognize acoustically and, perhaps, for some of them, to direct the operations.
The search for other marine mammals seems to unfold differently. The difficulty is not the same, since killer whales can also be detected acoustically from other cetaceans (whales and other dolphins) and visually by pinnipeds (sea lions, for example), they would have time to flee to their occurrence. Patrolling so silently, relying hearing to locate their prey, thanks to the noise they make these moving or signals they emit. They also know the places where whales, seals or sea lions are used 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, they are difficult opponents. To catch one, a number of killer whales coalesces: in order to immobilize it, the biting some fins, while others stick to the head biting his lip to force her to open her mouth; They may as well grab the tongue, very vulnerable part, true Achilles heel of the giant. Some whales can escape struggling violently. If you are located in the coastal area, their only chance of salvation is to take refuge in the shallow waters near the shore, where 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) coming out of the water quickly. For marine mammals the most effective method to escape a pack of ravenous killer whales it is to reach a school of fish. The observations show that in fact, if the fish is abundant, whale, sea lions and seals can approach safely to the orcas without fear of being mugged.
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 with fins and various caresses, and the partner will rub and roll against one another on the surface. After these preliminary steps, often also the coupling occurs at the surface, between a large amount of water splashes and vortices. The actual sex act is very short and lasts up to 30 seconds during which the animals mate in horizontal or vertical position, belly to belly, holding tight with the pectoral fins.
The duration of gestation is relatively long of 15 to 16 months, and the females give birth to a single pup, no more than once every three years. Childbirth and the first treatment given to the little ones are not very different from that observed for the other dolphins. The mother, probably 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 rapidly. The first year it seems that they only feed on breast milk and that will never turn away from the mother. When it wants to nurse, the calls with a tap of the muzzle into the belly, near the breast and, drunk with dexterity the jet of milk that comes out under pressure.
Sometimes you encounter subgroups of orcas composed only of infants and young. In reality, however, they are not alone, because there is always an adult nearby and its function is to monitor and, in some circumstances, also coordinate activities.
As in all cetaceans, the Orca growth occurs very rapidly during the first years of life. Then a decade, that of females slows sharply, 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 it is usually a weight difference with adult males weigh sometimes double of females (8:4 tons respectively).
The Orca age is evaluated based on the number of ivory layers that constitute the teeth. The maximum longevity so calculated is approximately 35 years. It must be said that, in nature, the orca has little to fear. Apart from humans and other killer whales, its enemies are few. However they are so tough that stand up well to the harpoons.
Spots: the three white patches that adorn the belly and the orca back are characteristic of the species. On the back, a crescent stain is placed, a bit 'like a saddle behind the dorsal fin; 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, occupies the entire ventral surface and takes the form of a trident.
Teeth: fifty teeth, of each length of 12-14 centimeters, have conical crown characterized by an internal flattening; They are implanted in a strong jaw, with strong muscles. They allow the animal to hold and tear prey of large size, as the whale or the smallest marine mammals (seals and sea lions).
Pectoral fin: the skeleton of the pectoral fin comprises the same bony elements of the forelimbs of mammals. The bones appear, however, strongly modified. The humerus, radius and ulna are particularly short and the last two are much flattened above and below. Only the joint between the humerus and the scapula is mobile, the others are sinartrosate, ie fixed. The hand is composed of five fingers wide apart, covered by a single envelope of fibrous tissue and skin, which gives the appearance to the fin of a double length racquet than the width. The second finger is longer and presents phalanges more developed than in the other fingers.