Orcinus orca, or killer whale, is a single cosmopolitan species, one of 35 in the oceanic dolphin family which first appeared on the planet about 11 million years ago.The killer whale lineage probably branched off shortly thereafter, and although it has morphological similarities with pilot whales and pygmy killer whales, its closest relative is the Irrawaddy dolphin.
With unmistakable black and white coloring, it is one of the best known of all the cetaceans. It has been extensively studied in the wild in many places around the globe, yet in Galapagos, although we occasionally see these magnificent animals on our Galapagos cruises, very little is really known about the individuals seen inside the waters of the archipelago.
An odontocete, or toothed whale, the orca is known for being carnivorous, a fast and skillful hunter, with a complex social structure. Sometimes called "the wolf of the sea", in Galapagos they have been seen eating everything from marine turtles to Risso’s dolphins to ocean sunfish.
Male orcas can grow as large as 32 feet (9.6 m) long and weigh 8 to 9 tons and females can reach 23 feet (8.2 m) in length and weigh up to 4 tons. Maturity is reached around 15 years for females, and gestation lasts around 15 to 18 months with births occurring roughly every five years. Females in the wild can live up to 50 years old, if not more. Calves have a high mortality rate of up to 50% in the first 6 months. In Galapagos they travel in small family groups, known as “pods”, and youngsters are often seen swimming in the slipstream alongside their mothers. Occasionally single animals are sighted, but with their excellent communication abilities, it is probable there are more in the area, which we are not aware of. Orca social structure matrilineal; the large male in a pod is the offspring of the matriarch. In the pod it is possible to have two or three generations, all descendants of the one female.
Over the last 30 years of research, it has been determined that there exist several “ecotypes” within this species. Individuals in these different “ecotypes” have discrete prey preferences, display unique behaviors and evidence different morphologies. Three “ecotypes” are recognized: a North Pacific, North Atlantic and Southern Oceans population. Recent studies of mtDNA variations indicate the three groups separated 150,000 to 700,000 years ago. There is little to no evidence that they interbreed.
In the Galapagos Islands, research on orcas has been difficult due to the large distances and sporadic appearances of these animals. Identification is done primarily through photographs of dorsal fins, preferably taken of the left side of the animal including the saddle-patch. Nicks and scratches can also help in the identification of individuals. Included with photographs should be GPS coordinates and time; please send in to the marine lab at the Charles Darwin Research Station.
Many species of smaller dolphins have been sighted in the Galapagos Islands, however two are by far the most commonly reported: the bottlenose dolphin Tursipos truncates andCommon dolphin Delphinus delphis.
Adult bottlenose dolphins off Great Britain can reach lengths from 8-12 feet (2.5-3.8 m) and can weigh as much as 1,430 pounds (650 kg); however most bottlenose dolphins are much smaller in other parts of the world with males being significantly larger than females. Bottlenose dolphins are found worldwide in temperate and tropical waters, absent only from 45 degrees poleward in either hemisphere.
In Galapagos these playful animals can be found bow-riding ships and boats as they travel between the islands, sometimes for hours at a time. Bow-riding can provide an animal with a free ride, energetically-speaking. Placing their tail stock in such a manner as to “surf” the pressure wave produced by the bow of the ship as it plows through the water, they are effortlessly pushed along for great distances. At times it seems they will choose to do this even if it takes them off course.
The common dolphin is found in all tropical and warm-temperate waters and can reach lengths of 7.5 - 8.5 feet (2.3-2.6 m) and weigh as much as 297 lb. (135 kg). In Galapagos they are seen most often in the western regions of the archipelago, although not exclusively. During the night they break into small groups, possibly family-related, but during the day gather into immense pods of hundreds of individuals. Although they are known to bow-ride in other places around the world, in Galapagos they do not approach vessels, rather preferring to stay away.
It was recently proposed that two forms of common dolphin exist: the short-beaked (Delphinus delphis) and long-beaked (Delphinus capensis) common dolphin. The short-beaked common dolphin is relatively heavier, and has a larger dorsal fin and flippers than the long-beaked common dolphin. The long-beaked common dolphin is foundmore in coastal waters; the short-beaked common dolphin is found in offshore waters and is the species that occurs frequently in the eastern tropical Pacific including Galapagos. Common dolphins have distinctive markings on their flanks in a colorful complex crisscross or hourglass pattern; the long-beaked common dolphin is more muted in color.
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