Orca (Orcinus orca) is the family member of larger dolphins and is a versatile superpredator, which includes in its diet prey such as fish, mollusks, birds, turtles, seals, sharks, and larger animals when hunting in groups, such as whales. Although “killer whale” is an incorrect designation, because it is a direct translation of the English “killer whale”, and because the animal is not a whale, it is commonly used. It is the second mammal with the largest geographical distribution area – right after a man – is found in all oceans and can weigh nine tons.
They have a complex social life, based on the formation and maintenance of extended family groups. They communicate through sounds and often travel in formations that occasionally sum on the surface. The first description of the species was made by Pliny the Old Man who already described it as a ferocious sea monster.
The name orca was given to these animals by the ancient Romans of the name “Orcus”, which means hell or god of death, and the name of their biological genus – “Orcinus” – means “of the kingdom of death” (see Orco). From the 1960s, when they gained popularity among oceanarium viewers, the term neutral “orca” was more used than “killer whale”, which connotes behavior incompatible with the goal of these parks.
These animals are characterized by having the black back and the white ventral zone. They also have white spots on the backside of the body, as well as above and behind the eyes. With a heavy, entropy body, they have the largest dorsal fin in the animal kingdom, which can measure up to 1.8 meters high (larger and more erect in males than in females). Males can measure from 9.8 to 10 meters in length and weigh up to 9,000 – 10,000 kg (9 – 10 tons); females are smaller, reaching 8.5 meters and 6,500 – 7,500 kg (between 6 and 8 tons), respectively. The chicks are born about 180 kg and measure about 2.4 meters in length.
Larger male orcas have a distinct aspect that gives no room for confusion when identified. However, seen at a distance in temperate waters, females, and offspring can be confused with other species, such as false-orca or big dolphin.
Most of the data on the lives of orcas were obtained in long-term surveys with populations off the coast of British Columbia and Washington, as well as by observing captive animals. The information available about this species is large and is properly systematized by naturalists, which is also due to the highly structured nature of the social groups of these animals. However, transient groups or residents in other geographical areas may have slightly different characteristics. Females reach sexual maturity at 15 years of age. From this point on, they have periods of a polyestrous cycle (regular and continuous heat) with periods without the central cycle that can last from three to sixteen months. Females can give birth to one offspring once every five years.
In the social groups analyzed, births can occur at any time of the year, with a certain preference for winter. The mortality of newborns is high – the results of an investigation suggest that about half of the offspring die before reaching six months. The chicks are breastfed until the age of two, but at twelve months already feed on solid food. Females are fertile up to 40 years of age, which, on average, means they can have up to five chicks. The life expectancy of females is usually fifty years old, even if in exceptional cases they can live up to ninety years. Males become sexually active at the age of 15 and come to live up to 30 years (or up to 50 in exceptional cases).