Balaenoptera musculus ssp. intermedia
|Scientific Name:||Balaenoptera musculus ssp. intermedia|
|Species Authority:||Burmeister, 1871|
Balaenoptera musculus (Linnaeus, 1758)
The sub-specific taxonomy of blue whales is not yet fully elucidated in all regions, but the Antarctic blue whale is distinguished by its large body size and Antarctic distribution in summer. It is morphologically distinct from its neighbouring subspecies, the pygmy blue whale B. m. brevicauda (Ichihara 1966), but only a limited number of the distinguishing characteristics are discernible at sea, making field differentiation between the two subspecies imperfect (Kato et al. 2002). The ranges of the two subspecies do not overlap in summer (Kato et al. 1995, Branch 2006) but they may overlap in winter if the Antarctic blue whale migrates into pygmy blue whale habitat. The morphological distinction between Antarctic blue whales and those off western South America is not always clear (van Waerebeek et al. 1997, Palacios 1999) but the summer presence of the southeastern Pacific whales and the gap in summer sightings of blue whales between 44°S in Chile and the Antarctic implies that the Antarctic whales are geographically well separated from the southeastern Pacific whales. LeDuc et al. (2007) found that Antarctic blue whales were genetically distinct at the population level from pygmy blue whales and southeastern Pacific whales, but no definitive, diagnostic genetic marker for the Antarctic blue whale has been found to date. A recent acoustic study has shown that the sounds produced by Antarctic and pygmy blue whales are distinct (Ljungblad et al. 1998). The unique songs produced by both forms are also different from those produced by other blue whales world-wide (McDonald et al.2006).
|Red List Category & Criteria:||Critically Endangered A1abd ver 3.1|
|Assessor(s):||Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N.|
|Reviewer(s):||Taylor, B.L. & Notarbartolo di Sciara, G. (Cetacean Red List Authority)|
The population is less than 3% of its level of three generations ago (at least a 97% decline) (1914-2007), and therefore qualifies for CR under the reduction criterion A1 based on a combination of direct recent observations, and inferred reductions from known past catches (subcriteria a, b, d).
|Previously published Red List assessments:||
The Antarctic blue whale occurs in summer between the Antarctic Polar Front and into the pack ice zone, being most abundant near the ice edge (Branch et al. 2007). Modern sightings are aggregated close to the edge of the pack ice, while past catches extended further north. Whether this is due to retreat of the pack ice since the time of catching (de la Mare 1997), or because the distribution of the species has contracted following exploitation, is unclear. Over 40,000 blue whales were caught in the waters around
The winter distribution is poorly known, except that Antarctic blue whales occur in winter around southern Africa (including
Native:Angola (Angola); Antarctica; Argentina; Australia; Chile; Congo; Falkland Islands (Malvinas); French Southern Territories; Indonesia; Namibia; South Africa; South Georgia and the South Sandwich Islands (South Georgia, South Sandwich Is.)
|FAO Marine Fishing Areas:||
Atlantic – Antarctic; Indian Ocean – Antarctic; Pacific – Antarctic
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The Antarctic blue whale
was extremely abundant in the past; about 341,830 blue whales were recorded
caught in the Antarctic and sub-Antarctic (IWC 2006) in the 20th
century, of which 12,618 were identified as pygmy blue whales or are assumed to
have been so from their location (Branch et
al. 2004). About 40,000 of these
were taken around
|Current Population Trend:||Increasing|
|Habitat and Ecology:||
Antarctic blue whales are the largest living animal, with lengths up to 33.6m. They feed almost exclusively on euphausiids (krill), especially Euphausia superba (Mackintosh and Wheeler 1929). In summer they feed predominantly near the edge of the pack ice zone.
|Movement patterns:||Full Migrant|
The main threat in the
past was direct exploitation, which only became possible (on more than an
occasional basis) in the modern era using deck-mounted harpoon cannons. Whaling
on Antarctic blue whales began in 1904 based in
Blue whales are protected worldwide, including the Antarctic, by the International Whaling Commission, and no hunting currently occurs.
The species is on Appendix I of both CITES and CMS.
|Citation:||Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Balaenoptera musculus ssp. intermedia. The IUCN Red List of Threatened Species 2008: e.T41713A10543676. . Downloaded on 06 October 2015.|
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