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Possible fourth species of Killer whale identified

25/06/2013 15:26:49
whales/nov_2009/killer_whales_noaa

Three different Antarctic killer whales: Top - Type A; Middle - Type B; Bottom - Type C were recognised in 2010, and now a 4th, Type D, has been identified (as designated by Pitman and Ensor, J. Cetacean Research and Management.

New technology supports evidence of multiple species
June 2013. In April 2010, scientists reported finding strong genetic evidence supporting the theory that there are at least three species of killer whales (Orca) in the world's oceans. New evidence suggests that a fourth species, type D, has been identified.

Type D
The first possible sighting of the new ‘Type D' was in 1955 when a pod of unusual-looking orca stranded on a beach in New Zealand. Recent photographs of similar orca from the southern Indian Ocean reveal that they have a very small white eye-patch and bulbous forehead. Analysis of a skeleton from the 1955 stranding, now in a museum in Wellington, indicates that ‘Type D' is highly divergent from all previously genetically sequenced killer whale forms. The estimated divergence was as long ago as 390,000 years, the second oldest split within the killer whale phylogeny.

Very different behaviour patterns
Scientists have suspected for some time that there was more than one species of killer whales because of differences in behaviour, feeding preferences and subtle physical features.

The following killer whales were recognised as separate species in 2010: 

Type-B "pack ice killer whale" from the Antarctic. Note the large eye-patch and two-tone gray color pattern. This type specializes in hunting seals, which are often on the ice and need to be knocked off the ice by the whales before they can be caught. 

Photo Credit: Bob Pitman, NOAA Southwest Fisheries Science Center 



Type-C "Ross Sea killer whale" from the Antarctic. Note the narrow angled eye patch. These are the smallest of the 3 Antarctic types and they eat fish that are found primarily under the ice pack, so they follow leads deep into the ice as it breaks up in the summer months.

Photo Credit: Bob Pitman, NOAA Southwest Fisheries Science Center 

Type-A killer whale from the Antarctic. Note the striking black and white colour pattern. This type is found in open water areas and feeds primarily on other cetaceans (whales and dolphins).  

Photo Credit: John Durban, NOAA Southwest Fisheries Science Center 

NE Pacific Transient killer whale in Alaska. Note the typical black and white colour pattern and eye-patch, similar to Antarctic Type A killer whales (left), but genetically distinct. The Transients are known to feed on all types of marine mammals, including other whales, dolphins, and seals and sea lions. 

Photo Credit: Dave Ellifrit, NOAA Alaska Fisheries Science Center 

139 killer whale samples analyzed - Several species identified
In all, tissue samples from 139 killer whales were analyzed. Samples came from killer whales found in the North Pacific, the North Atlantic and oceans surrounding Antarctica. As a result of the study, two types of killer whales in the Antarctic that eat fish and seals, respectively, are suggested as separate species, along with mammal-eating "transient" killer whales in the North Pacific. Several other types of killer whales may also be separate species or subspecies, but additional analysis is required.

These findings also highlight the value of natural history museum collections and new technologies to investigate the taxonomy of rare, cryptic or difficult to access species. 

Read more information in the journal Polar Biology 

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