Balaenidae () is a
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of
whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s of the
parvorder Mysticeti
Baleen whales (systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea (whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in their ...
that contains two living genera: the right whales (genus ''
Eubalaena''), and in a separate genus, the closely related bowhead whale (genus ''
Balaena'').
Evolutionary history
Baleen whale
Baleen whales (systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea (whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in their ...
s belong to a monophyletic lineage of
Mysticeti
Baleen whales (systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea (whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in their ...
. Mysticeti are large filter-feeding
cetacea
Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
ns that also include some of the largest animals on earth as well as some of the most critically endangered.
[''Kaliszewska, Z. A.J. SegerV. Rowntreeet al2005Population histories'' of right whales (Cetacea: Eubalaena) inferred from mitochondrial sequence diversities and divergences of their whale lice (Amphipoda: Cyamus)Molecular Ecology1434393456] Based on morphology and molecular data, four extant family-level clades are recognized within Mysticeti: Balaenidae (bowhead and right whales), Neobalaenidae (pygmy right whales), Eschirichtiidae (gray whales), and Balaenopteridae (rorquals).
Phylogenetic relationships of the mysticeti order remain unclear due to legal and logistical challenges.
However, recent morphological analysis, support Balaenidae as a monophyletic group that is the sister group to Neobalaenidae.
Characteristics
Balaenids are large whales, with an average adult length of 15 to 17 metres (45–50 feet), and weighing 50-80 tonnes. Their principle distinguishing feature is their narrow, arched, upper jaw, which gives the animals a deeply curved jawline. This shape allows for especially long
baleen
Baleen is a filter-feeding system inside the mouths of baleen whales. To use baleen, the whale first opens its mouth underwater to take in water. The whale then pushes the water out, and animals such as krill are filtered by the baleen and ...
plates. The animals utilise these by
ram feeding
Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identifi ...
, swimming at or near the surface with their mouth open for minutes at a time, and straining food from the water, which they then scrape off the baleen with their tongues
– a feeding method that contrasts with those of the
rorqual
Rorquals () are the largest group of baleen whales, which comprise the family Balaenopteridae, containing ten extant species in three genera. They include the largest animal that has ever lived, the blue whale, which can reach , and the fin wha ...
s and the
gray whale
The gray whale (''Eschrichtius robustus''), also known as the grey whale,Britannica Micro.: v. IV, p. 693. gray back whale, Pacific gray whale, Korean gray whale, or California gray whale, is a baleen whale that migrates between feeding and bree ...
.
Their diet consists of small
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s, primarily
copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...
s, although some species also eat a significant amount of
krill.
Similarities in terms of physical appearances of jawlines and usages between balaenidae and
flamingo have been pointed as a result of possible
convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
.
Balaenids are also robustly built by comparison with the rorquals, and lack the grooves along the throat that are distinctive of those animals. They have exceptionally large heads in comparison with their bodies, reaching 40% of the total length in the case of the
bowhead whale
The bowhead whale (''Balaena mysticetus'') is a species of baleen whale belonging to the family Balaenidae and the only living representative of the genus ''Balaena''. They are the only baleen whale endemic to the Arctic and subarctic waters, ...
. They have short, broad, flippers, and lack a dorsal fin.
All species are at least somewhat migratory, moving into warmer waters during the winter, during which they both mate and give birth.
Gestation
Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
lasts 10–11 months, results in the birth of a single young, and typically occurs once every three years.
Distribution
The four species of the Balaenidae are found in temperate and polar waters; ''
Eubalaena glacialis'' (North Atlantic right whale), ''
Eubalaena japonica'' (North Pacific right whale), ''
Eubalaena australis'' (southern right whale), and ''
Balaena mysticetus'' (bowhead whale). Bowhead and right whales can reach up to 18 meters in length and over 100 tons at maturity.
Exploitation and conservation status
Members of Balaenidae can live over 70 years and were hunted extensively in the late 1800s
for their blubber. Approximately 40% of right whales' body mass is blubber, and
thus they were known as the "right" whale to kill.
[Eubalaena glacialis (Müller, 1776) North Atlantic right whale, Encyclopedia of Life, accessed 11-30-2015] After death,
the large blubber deposits caused right whales to float to the surface, which
facilitated an easier oil harvest. With a population estimated at between 300-350 individuals,
the North Atlantic right whale is the most critically endangered great whale. The
Northern Pacific right whale is also endangered with only about 500 individuals
extant.
The Southern right whale (~7500 individuals in
1997) and the Bowhead whale (20,000 to 40,000) have made stronger recoveries
since whale hunting was significantly curtailed by international agreement.
Taxonomy
*Family Balaenidae
**Genus ''
Balaena''
***
Bowhead whale
The bowhead whale (''Balaena mysticetus'') is a species of baleen whale belonging to the family Balaenidae and the only living representative of the genus ''Balaena''. They are the only baleen whale endemic to the Arctic and subarctic waters, ...
, ''Balaena mysticetus''
**Genus ''
Eubalaena''
***
North Atlantic right whale, ''Eubalaena glacialis''
***
North Pacific right whale, ''Eubalaena japonica''
***
Southern right whale
The southern right whale (''Eubalaena australis'') is a baleen whale, one of three species classified as right whales belonging to the genus ''Eubalaena''. Southern right whales inhabit oceans south of the Equator, between the latitudes of 20 ...
, ''Eubalaena australis''
Until recently, all right whales of the genus ''Eubalaena'' were considered a single species—''E. glacialis''. In 2000, genetic studies of right whales from the different ocean basins led scientists to conclude that the populations in the North Atlantic, North Pacific and Southern Hemisphere constitute three distinct species.
Further genetic analysis in 2005 using mitochondrial DNA and nuclear DNA has supported the conclusion that the three populations should be treated as separate species,
and the separation has been adopted for management purposes by the U.S. National Marine Fisheries Service and the International Whaling Commission.
[National Marine Fisheries Service: Review of the Status of the Right Whales in the North Atlantic and North Pacific Oceans (2006)]
(PDF). Retrieved September 15, 2011.
The
cladogram is a tool for visualizing and comparing the evolutionary relationships between
taxa. The point where a node branches off is analogous to an evolutionary branching – the diagram can be read left-to-right, much like a timeline. The following cladogram of the family Balaenidae serves to illustrate the current scientific consensus as to the relationships between the North Pacific right whale and the other members of its family.
References
External links
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{{Authority control
Baleen whales
Mammal families
Taxa named by John Edward Gray