Friday, February 13, 2015


The dusky dolphin (Lagenorhynchus obscurus) is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithetis Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, but current scientific consensus holds they are distinct species. The dolphin's range is patchy, with major populations around South America, southwestern AfricaNew Zealand, and various oceanic islands, with some sightings around southern Australia and Tasmania. The dusky dolphin prefers cool currents and inshore waters, but can also be found offshore. It feeds on a variety of fish and squid species and has flexible hunting tactics. The dusky dolphin is known for its remarkable acrobatics, having a number of aerial behaviors. The status of the dolphin is unknown, but it has been commonly caught in gill nets.

he dusky dolphin and the Pacific white-sided dolphin are considered phylogenetically related species. Some researchers have suggested they are the same species, but morphological and life-history evidence shows otherwise. The two sister species diverged at around 1.9–3.0 million years ago.Dusky dolphins from Argentina and southwest Africa separated 2000 generations ago from an ancestral Atlantic are four subspecies classified; (Lagenorhynchus obscurus obscurus), (L. o. fitroyi), (L. o. posidonia) and (L. o. superciliosis).The dusky dolphin is best known for his striped like appearance and its incredible acrobatic character.Possible hybrids of dusky dolphins have been described with a long-beaked common dolphin and a southern right whale dolphin.The dusky dolphin is small to medium in length compared with other species in the family. There is significant variation in size among the different population areas. The largest dusky dolphins have been encountered off the coast of Peru, where they are up to 210 cm (6 feet) in length and 100 kg (210 pounds) in mass. The size for dusky dolphins in New Zealand have been recorded to be a length range of 167–178 cm and a weight range of 69–78 kg for females and a length range of 165–175 cm and a weigh range of 70–85 kg for males.

The males have have more curved dorsal fins with broader bases and greater surface areas.he back of the dolphin is dark grey or black, and the dorsal fin is distinctively two-toned; the leading edge matches the back in color, but the trailing edge is a much lighter greyish white. The dusky dolphins has a long, light-grey patch on its fore side leading to a short, dark-grey beak. The throat and belly are white, and the beak and lower jaw are dark grey. Two blazes of white color run back on the body from the dorsal fin to the tail. Right between the white areas remains a characteristic thorn-shaped patch of dark color, by which the species can easily be recognized. Aside from that, dusky dolphins may be confused with other members of their genus when observed at sea. It can be distinguished from the common dolphin, which has a more prominent and longer beak and yellow flank markings. The skull of a dusky dolphin has a longer and narrower rostrum than that of an hourglass dolphin or Peale's dolphin of similar age and size.

The dolphins can be found off the coasts of South America, southwestern Africa, southern Australia and Tasmania, New Zealand, and some oceanic islands.Dusky dolphins are found throughout New Zealand waters.Dusky dolphins prefer cool, upwelling waters, as well as cold currents. They largely live in inshore waters and can be found up to the outer continental shelf and in similar zones in offshore islands.They can move over great distances (around 780 km), but have no well-defined seasonal migrations. However, dolphins off Argentina and New Zealand make inshore and offshore seasonal and diurnal movements.They have been found around bottlenose dolphins, but apparently do not interact with them, and may share feeding areas with Risso's dolphins.

Dusky dolphins prey consume a variety of fish and squid species. Common fish species eaten include anchovieslantern fish,pilchardssculpinshakeshorse mackerelhoki and red cod. They are generally coordinated hunters. Their very flexible foraging strategies can change depending on the environment. In certain parts of New Zealand, where deep oceanic waters meet the shore, dusky dolphins forage in deep scattering layers at night. They arrive at the hunting site individually, but form groups when in the layer. The dolphins use their echolocation to detect and isolate an individual prey. Groups of foraging dolphins tend to increase when the layer is near the surface and decrease when it descends.The dolphins chase schools of fish or squid and herd them into stationary balls. They may control the school with light reflected from their white bellies.Dolphins herd prey against the surface, but also horizontally against the shore, a point of land, or the hull of a boat.During these times, dusky dolphins are believed to increase prey availability for other predators, including other dolphins, seabirds,sharks, and pinnipeds.
Dusky dolphins perform a number of aerial displays, including leaps, backslaps, headslaps, tailslaps, spins, and noseouts.They also perform head-over-tail leaps which have been called the most "acrobatic" of the displays. A headfirst re-entry is performed when a dolphin leaps entirely water and positions its back in a curve while it flips the tail to land back in the water head-first. "Humping" is similar, except the snout and tail remain in the water when the dolphin is the arch. Leaps, head-over-tail leaps, backslaps, headslaps, tailslaps, and spins are often done over and over again. Young dusky dolphins apparently are not born with the ability to perform the leaps and must learn to master each one Calves appear to learn the leaps in this order: noisy leaps, head first re-entries, coordinated leaps, and acrobatic leaps.Adults may perform different leaps in different contexts, and calves may independently learn how to perform leaps, but learn when to perform these when interacting others.

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