The age of fin whales, as other rorquals (balaenopteridae), can be estimated by counting the growth layers present in waxy ear plugs, which are formed in the auditory canal (Lockyer 1984, Hohn 2002). Fin whales can live 80-90 years. The oldest specimen captured off Iceland was 94 years old (Konráðsson & Gunnlaugsson 1990) and off Antarctica 111 years old.
Ear plug from a 57-year old Icelandic fin whale. Photo: C. Lockyer
The biology of fin whales sampled from the Icelandic catch has been studied between 1977 and 1989 (Lockyer and Sigurjónsson 1992). In this area a female fin whale first gives birth at an age between 7 and 12 years, and a male reaches sexual maturity at about 6-10 years of age. The age of sexual maturity for both sexes has varied significantly over time, possibly in response to food availability and/or hunting pressure (e.g. Williams et al. 2013). Physical maturity is attained at approximately 25 years for both sexes.
Fin whales have generally a two-year reproductive cycle, with gestation taking about 11 months and resulting in a single calf born in mid winter. Newborn calves are approximately 6 m long and weigh two tonnes. Calves nurse for 6–8 months and are weaned when they are 10 to 12 m in length, when they travel with their mother to the feeding grounds. Mating and calving are thought to occur during the winter months, but no specific mating or calving “grounds” have been reported for fin whales.
The two-year reproductive cycle of North Atlantic fin whales (from Lockyer 1987)
Several hybrids of fin and blue whales, some pregnant, have been documented and 5 were genetically confirmed (Árnason et al. 1991, Spilleart et al. 1991, Bérubé and Aguilar 1998, Cipriano and Palumbi 1999). The hybrids, three females and two males, were all taken in commercial whaling operations in the Northern Hemisphere. In 2014 a new blue/fin hybrid was caught, and this whale had a fetus that was ¾ blue whale.
A hybrid of fin and blue whale at the Icelandic whaling station. Photo: Marine Research Institute
Fin whales are known to have a broad diet in the North Atlantic, including krill, copepods and pelagic fish such as capelin, juvenile herring and blue whiting (Sergeant 1966, Mitchell 1975, Overholtz and Nicholas 1979, Woodley and Gaskin 1996, Sigurjónsson and Víkingsson 1997, Bloch and Joensen 1985). Squid may also be eaten in some areas. In the North East Atlantic the main prey seems however, to be the swarming euphausiids Meganyctiphanes norvegica.
Although the fin whale is more flexible in its diet than the blue whale (B. musculus), its consumption of fish does not necessarily make it a significant competitor with fisheries (Reilly et al. 2008).
Fin whales can consume up to 3 tonnes of food a day. Feeding activity, however, varies greatly by season due to variation in prey abundance. It is vital for fin whales to build up energy reserves in the form of stored fat and blubber during the summer, since preys are less available in the wintering areas. During winter, daily food intake may be as low as a tenth of the summer intake.
Due to its large size and fast swimming, the fin whale has very few natural predators. Calves and even adults may occasionally be taken by killer whales.
|See a pod of killer whales chasing a fin whale.|