Facts About Dusky Dolphins
By zteve t evans
Dusky Dolphins (Lagenorhynchus obscurus) live in groups of of 15 to 500 though groups of several thousand individuals are known. They live in fission-fusion societies with individuals moving from group to group as and when it suits them. When feeding they tend to split into small groups but when finished will again join up with other groups to rest or socialise.
They are very social animals and like the company of their own species while appearing to be comfortable with that of many others. They are known to associate with variety of other species of dolphin and whales as well as seals, sea birds and also humans.
They are very social animals and like the company of their own species while appearing to be comfortable with that of many others. They are known to associate with variety of other species of dolphin and whales as well as seals, sea birds and also humans.
Acrobatic Displays
They are very curious dolphins and often approach boats and interact with people in the water. Dusky dolphins are very acrobatic often making high leaps and somersault high out of the water. They can put on a stunning performance that included tail slaps, backslaps, head slaps, leaps, spins and no spouts and a variety of spectacular head over tail leaps. They will often repeat this behavior dozens of times. Quite often when one starts this behaviour others will follow.
Range of the Dusky Dolphin Map of their range
Dusky dolphins are similar in appearance to Pacific white-sided dolphins and although genetically similar they are recognised as a different species. There are three recognised subspecies of dusky dolphins and have been classified by region with all having slight differences in physique physique and behaviour These are L. obscurus fitzroyi found off South America, L. obscurus obscurus found in the Indian Ocean and L. obscurus subsp found off New Zealand.
They live throughout the temperate waters of the Southern hemisphere liking continental shelves and coastal waters. There are three main populations in South America, including the Falkland Islands, southwestern Africa, and New Zealand including Chatham, Auckland, and Campbell Islands. They seem more populous in the northern parts of their range in winter and during summer prefer southern parts.
They are very curious dolphins and often approach boats and interact with people in the water. Dusky dolphins are very acrobatic often making high leaps and somersault high out of the water. They can put on a stunning performance that included tail slaps, backslaps, head slaps, leaps, spins and no spouts and a variety of spectacular head over tail leaps. They will often repeat this behavior dozens of times. Quite often when one starts this behaviour others will follow.
Range of the Dusky Dolphin Map of their range
Dusky dolphins are similar in appearance to Pacific white-sided dolphins and although genetically similar they are recognised as a different species. There are three recognised subspecies of dusky dolphins and have been classified by region with all having slight differences in physique physique and behaviour These are L. obscurus fitzroyi found off South America, L. obscurus obscurus found in the Indian Ocean and L. obscurus subsp found off New Zealand.
They live throughout the temperate waters of the Southern hemisphere liking continental shelves and coastal waters. There are three main populations in South America, including the Falkland Islands, southwestern Africa, and New Zealand including Chatham, Auckland, and Campbell Islands. They seem more populous in the northern parts of their range in winter and during summer prefer southern parts.
Physical Description
Dusky dolphins can grow up to 2.1 metres in length and weigh up to 90 kilograms. They have a small, robust body that has a white underbelly and a predominantly dark upperside. On each of its sides it has two pale grey or white blazes, while on its bach is a falcate two-toned fin. It has a thick short dark beak, mostly white face, with small black patches around each eye.
Diet and Hunting
Dusky dolphins eat squid and fish such as lantern fish,anchovies, sculpins, pilchards, hoki, hakes, red cod and horse mackerel. They have very flexible hunting methods and are also known to engage in cooperative hunting. For example, Dusky dolphins of Argentina and New Zealand tend to hunt in daylight. They are known to round up schools of squid or fish into stationary balls in the water before attacking. It is thought that they may control the school by using light reflected from their white underbellies.
Other tactics include herding prey towards the water’s surface forcing them horizontally against a fixed point such a point of land, the shore or even a boat. These strategies are believed to benefit other predators such as sharks, seals, seabirds and other dolphins species. They are also believed to locate schools of prey by looking for places where birds are congregating.
Sharks and killer whales are the natural enemies of Dusky dolphins who try and avoid predators by swimming into shallower water.
Breeding and Reproduction
During mating males will often chase the females at high speed. Females seem to prefer males who are agile and capable of high speed rather than looking for strength, size or aggression. Females tend to extend their pursuit to keep only the best males in the chase and will evade males who lack vigor or social skills. Sometimes males work together to catch a female and unlike some species such as Bottlenose dolphins, Dusky males do not tend to monopolise females.
Nursery Groups
Females with calves often work together to form nursery groups in shallow waters. This gives them the opportunity for a well earned rest and provides extra security. It also allows them to hunt fish in the shallows and teach their young how to hunt safely. Calves are especially vulnerable to predators such as sharks and Orca whales who prefer to attack in deep water.
Status
The IUCN lists the Dusky dolphin as Data Deficient in most of its range which means there is not enough information available to make an assessment on the abundance of their worldwide population. It is believed that the subpopulation of Dusky dolphins off Peru have been killed in large numbers for shark bait and human consumption and those off Chile have also suffered. In other areas of their range are trapped accidently in gill nets.
Copyright 27/09/2014 zteve t evans
Dusky dolphins can grow up to 2.1 metres in length and weigh up to 90 kilograms. They have a small, robust body that has a white underbelly and a predominantly dark upperside. On each of its sides it has two pale grey or white blazes, while on its bach is a falcate two-toned fin. It has a thick short dark beak, mostly white face, with small black patches around each eye.
Diet and Hunting
Dusky dolphins eat squid and fish such as lantern fish,anchovies, sculpins, pilchards, hoki, hakes, red cod and horse mackerel. They have very flexible hunting methods and are also known to engage in cooperative hunting. For example, Dusky dolphins of Argentina and New Zealand tend to hunt in daylight. They are known to round up schools of squid or fish into stationary balls in the water before attacking. It is thought that they may control the school by using light reflected from their white underbellies.
Other tactics include herding prey towards the water’s surface forcing them horizontally against a fixed point such a point of land, the shore or even a boat. These strategies are believed to benefit other predators such as sharks, seals, seabirds and other dolphins species. They are also believed to locate schools of prey by looking for places where birds are congregating.
Sharks and killer whales are the natural enemies of Dusky dolphins who try and avoid predators by swimming into shallower water.
Breeding and Reproduction
During mating males will often chase the females at high speed. Females seem to prefer males who are agile and capable of high speed rather than looking for strength, size or aggression. Females tend to extend their pursuit to keep only the best males in the chase and will evade males who lack vigor or social skills. Sometimes males work together to catch a female and unlike some species such as Bottlenose dolphins, Dusky males do not tend to monopolise females.
Nursery Groups
Females with calves often work together to form nursery groups in shallow waters. This gives them the opportunity for a well earned rest and provides extra security. It also allows them to hunt fish in the shallows and teach their young how to hunt safely. Calves are especially vulnerable to predators such as sharks and Orca whales who prefer to attack in deep water.
Status
The IUCN lists the Dusky dolphin as Data Deficient in most of its range which means there is not enough information available to make an assessment on the abundance of their worldwide population. It is believed that the subpopulation of Dusky dolphins off Peru have been killed in large numbers for shark bait and human consumption and those off Chile have also suffered. In other areas of their range are trapped accidently in gill nets.
Copyright 27/09/2014 zteve t evans
References and Attributions
Copyright 27/09/2014 zteve t evans
Copyright 27/09/2014 zteve t evans
- File:DuskyJump.jpg From Wikimedia Commons - dusky dolphins named "Caligo" and "Umber".- Author: AllenMcC - Creative Commons Attribution-Share Alike 3.0 Germany
- Society for Marine Mammalogy - Dusky dolphin (L. obscurus)
- Dusky dolphin - Wikipedia, the free encyclopedia
- Dusky Dolphins, Lagenorhynchus obscurus ~ MarineBio.org
- Dusky dolphin: New Zealand marine mammals