Fin Whale ( Balaenoptera physalus )

/ / Marine Mammals

Description

The Fin Whale is one of the rorqual whales. Rorqual whales (including the Blue whale (Balaenoptera musculus), the Humpback whale (Megaptera novaeangliae) and the Sei whale (Balaenoptera borealis) all have throat grooves which expand when feeding and dorsal fins (1).

Fin whales are dark grey to brown/black in colour (1; 2; 3) with a white belly and underside of fins (3). Their colouration is asymmetrical on their lower jaw, the right side is creamy-white while the left side is brownish-grey or black (1; 2). They also have lighter grey ‘chevrons’ on their back, starting just behind the head (1; 2; 3).

The dorsal fin is tall and can be more than 60cm high (3). It is falcate (slightly curved) (1; 2) and positioned 1/3 of the body length before the fluke (3). Pectoral fins are relatively short and tapered and the fluke is wide and pointed at the tips (1; 3).

The maximum length of Fin whales in the Northern hemisphere is 24m (2; 3) however mean length has been reported as 13.8m in the Mediterranean (4). Females are typically longer than males (4).

Behaviour

B. physalus are social marine mammals, their large vocal range enables them to maintain communication and social cohesion over large distances, even when they may seem solitary (4).

B. physalus is one of the fastest whales, capable of bursts of speed up to 37km/hr (1). Fin whales are lunge feeders, and their speed enables them to catch mobile prey of krill and fish (5). They can dive to at least 470m in order to catch prey (6).

Fin whales are not aerially acrobatic, unlike the Humpback whale (M. novaeangliae), however, they have been observed breaching in the Mediterranean (4).

Life Cycle

Like many of the rorqual whales, B. physalus’ reproductive cycle is synchronised with their feeding migrations. They mate during winter and the pregnant females will spend the longest in summer feeding grounds in order to accumulate enough fat to support lactation and the survival of the single calf (7). Gestation period is 11 months; the calf is born in the warmer winter grounds and is weaned before the migration to colder summer feeding grounds (8; 7). Male fin whales are approximately 19m when they reach sexual maturity, and females are 20m (7). Calves are born at a mean length of 6m (8) and are approximately 11.5m length at weaning (7). This pattern is the same in the Mediterranean, however, the calving period is longer, possibly due to the different environmental conditions in the Mediterranean; milder climate and possibly longer availability of seasonal food (4).

Hybridisation has been known to occur between B. physalus and B. musculus (7). A female hybrid was found to be pregnant, showing that this hybridisation can produce fertile offspring (9); however, it is thought that male hybrids are sterile (7).

Habitat

Fin whales are pelagic, usually occurring over deep off-shore waters (10). However, in the Mediterranean they have been observed in waters less than 1000m deep (11). It is thought that this is due to the density of prey (4).

Distribution

B. physalus occurs worldwide, mainly in offshore waters (10). Fin Whales mainly occur in the Western Mediterranean Sea; however they also occur, rarely, in the Eastern Mediterranean Sea (4).

Food

Fin whales have between 260-480 baleen plates that are approximately 72cm long and 30cm wide (3). The long throat grooves, characteristic of the rorqual whales, allow large amounts of water and food to be taken into the mouth (1). Fin whales mainly feed on krill species, but are known to supplement their intake with schooling fish, such as capelin and herring (8). It is thought that the whales feed on krill during the summer months and fish in the winter months (12).

Conservation Status

IUCN Red List: Endangered (13)

CITES Appendix I (14)

Bern Convention Appendix II (15)

CMS Appendices I and II (16)

References

Description written by Sarah Marjoram (2009)

(1)   (ACS), A.C.S., 2009. American Cetacean Society Fact Sheet – Fin Whale (Balaenoptera physalus). [Online] Available at: http://www.acsonline.org/factpack/finwhl.htm [Accessed 27 July 2009].

(2)   FAO, n.d. Species Fact Sheet – Balaenoptera physalus. [Online] Available at: http://www.fao.org/fishery/species/3601/en [Accessed 27 July 2009].

(3)   Sisak, M.M., n.d. Balaenoptera physalus. [Online] Available at: http://www.cites.org/eng/resources/ID/fauna/Volume1/A-111.007.001.005%20Balaenoptera%20physalus_E.pdf [Accessed 27 July 2009].

(4)   Notarbartolo-di-Sciara, G..M.Z.M.J.S.P.a.S.A., 2003. The fin whale Balaenoptera physalus (L. 1758) in the Mediterranean Sea. Mammal Review, 33(2), pp.105-50.

(5)   Wells, R.S..D.J.B.a.G.B.R., 1999. Behaviour. In Reynolds III, J.E.a.S.A.R. Biology of Marine Mammals. Washington and London: Smithsonian Institution Press.

(6)   Panigada, S..M.Z.S.C.a.M.J., 1999. How deep can baleen whales dive? Marine Ecology Progress Series, 187, pp.309-11.

(7)   Boyd, I.L..C.L.a.H.D.M., 1999. Reproduction in Marine Mammals. In Reynolds III, J.E.a.S.A.R. Biology of Marine Mammals. Washington and London: Smithsonian Institution Press.

(8)   Mizroch, S.A..D.W.R.a.J.M.B., 1984. The Fin Whale, Balaeloptera physalus. Marine Fisheries Review, 46(4), pp.20-24.

(9)   Spilliaert, R..G.V.U.A.A.P.J.S.a.A.A., 1991. Species Hybridization between a Female Blue Whale (Balaenoptera musculus) and a Male Fin Whale (B. physalus): Molecular and Morphological Documentation. The Journal of Heredity, 82(4), pp.269-74.

(10)           Reilly, S.B..J.L.B.P.B.B.M.B.R.L.B.J..D.S.B.P.J.C.J.C.G.P.D.J.U.&.A.N.Z., 2008. Balaenoptera physalus. [Online] (2009.1) Available at: www.iucnredlist.org [Accessed 28 July 2009].

(11)           Forcada, J..A.A.P.H.X.P.a.R.A., 1996. Distribution and abundance of fin whales (Balaenoptera physalus) in the western Mediterranean sea during the summer. Journal of Zoology, 238(1), pp.23-34.

(12)           Jonsgard, A., 1966. Biology of the North Atlantic Fin Whale, Balaenoptera physalus (L.): taxonomy, distribution, migration and food. Hvalradets Skrifter, 49, pp.1-62.

(13)           IUCN, 2009. IUCN Red List of Threatened Species. Version 2009.1. [Online] Available at: www.iucnredlist.org [Accessed 23 July 2009].

(14)           UNEP-WCMC, 2009. UNEP-WCMC Species Database: CITES-Listed Species. [Online] Available at: http://www.unep-wcmc.org/isdb/CITES/Taxonomy/tax-species-result.cfm/isdb/CITES/Taxonomy/tax-species-result.cfm?source=animals&displaylanguage=eng&genus=Physeter&species=catodon&tabname=legal [Accessed 23 July 2009].

(15)           Europe, C.o., 2002. Convention on the conservation of European wildlife and natural habitats: Bern Convention. [Online] Available at: http://conventions.coe.int/Treaty/FR/Treaties/Html/104-2.htm [Accessed 23 July 2009].

(16)            (CMS), C.o.t.C.o.M.S.o.W.A., Effective 5th March 2009. Appendices I and II of the Convention on the Conservation of Migratory Species of Wild Animals.