Evolution and systematics
The pygmy proper whale, Caperea marginata, is the smallest baleen whale and the one member of household Neobalaenidae. In the previous, it was placed among the many proper and bowhead whales (Balaenidae). It is now thought of to be a more in-depth relative to the rorquals (Balaenopteridae) and grey whales (Eschrichtiidae). DNA analysis from 1992 and 1993 by Úlfur Árnason and colleagues, in addition to morphological proof, have supported its membership in a separate household. Caperea marginata differs from different proper whales in having a proportionally smaller head and humerus, a unique kind of baleen, a dorsal fin, 4 digits as a substitute of 5, and 44 or fewer vertebrae. The cranium can be very completely different from these of the Balaenidae. The occipital protect is bigger, and initiatives farther to the fore. The rostrum is shorter, wider, and though it types much less of an arch, the arch turns into extra pronounced with age. The supraorbital processes are shorter. The nasal bones are smaller. The glenoid fossae and the orbits are much less ventrally placed than on the Balaenidae. No research of geographic variation have been performed, and there aren't any acknowledged subspecies. No fossils are identified. The taxonomy for this species is Caperea marginata (Gray, 1846), temperate waters of the Southern Hemisphere.
Caperea marginata is the smallest of the baleen whales. The biggest size and weight ever recorded are 21.Three ft (6.5 m) and seven,562 lb (3,430 kg). Caperea marginata is streamlined. Adults are heftier than rorquals however not as extensive as bowhead or proper whales. The comparatively giant head contains about one-fourth of complete size. The jawline arches after which reverses path simply northwest of the attention, considerably like a scythe or a query mark that has been laid over to the left and the sharp angle smoothed into a mild curve. The flippers, placed simply aft of and beneath the posterior finish of the jawline, are small and slender. Features that distinguish C. marginata from different proper whales include a small and strongly hooked dorsal fin 25-30% of physique size ahead from the tip of the flukes, and two throat grooves. The colour is darkish grey or black on the again, shading to paler on the stomach. The inside the mouth and tongue are ivory coloured, as is the gum on the base of the baleen. The baleen is lengthy and slender, with very fantastic bristles, and it's creamy white in colour apart from the margin, which varies from brown to black. Each facet of the jaw has 213 to 230 baleen plates, which measure up to 33 in (840-850 mm). The space of the filtering equipment is comparatively giant for the physique measurement. The skeleton and cranium are completely different from these of all different cetaceans. Caperea marginata has essentially the most ribs (34-36) and the least variety of vertebrae (40-44) of any cetacean. The ribs, extensive and flat, turn into extra so posteriorly, presumably to shield inside organs, and so they lengthen farther aft than these of every other genera, leaving solely two ribless vertebrae anterior to the tail. The seven cervical vertebrae are all fused.
The pygmy proper whale seems to inhabit the Southern Hemisphere between latitudes 31° and 52°, in each coastal and pelagic waters of the Atlantic, Pacific, and Indian Oceans. More sightings—greater than one-third of the entire—have taken place off the coast of southeastern Australia, primarily off Tasmania, than wherever else. Sightings and strandings have additionally occurred in South Africa, southern South America, New Zealand, The Falkland Islands, the Crozet Islands, and the south Atlantic Ocean.
Caperea marginata inhabits temperate and sub-antarctic waters in coastal and pelagic zones, between the 5° and 20° isotherms.
Little is thought about this small, obscure species, as a result of residing animals have been noticed solely hardly ever. There have been fewer than 20 observations of people or teams at sea, partly due to the animal’s inconspicuous conduct, and to the paucity of exercise on the floor. Pods of up to ten animals have been seen, and in a single occasion, roughly 80 people had been noticed collectively in pelagic waters, however most reside pygmy proper whales have been noticed singly or in pairs. Caperea marginata have been seen within the firm of dolphins and pilot (Globicephala melas), sei (B. borealis), and minke whales. Caperea marginata normally swims slowly, round three to 5 knots, however can speed up and swim in a short time if needed, propagating a notable wake. It swims by flexing its physique laterally, in waves. It doesn't seem to soar, and the blow is inconspicuous. Caperea marginata has been noticed to dive for under up to 4 minutes at a time, surfacing briefly between dives. Vocalizations are characterised as sounding like intense thumps or tone bursts, the amount of every rapidly rising, then slowly falling, whereas the frequency drops. They are available cycles of 11-19, every with a imply period of 180 m/sec, separated from one another by a imply of 460 m/sec. Strandings can happen at any time of 12 months, suggesting that pygmy proper whales could not migrate seasonally. However, elevated sightings and strandings within the waters off the Cape Peninsula of South Africa throughout December, January, and February have steered a seasonal migration throughout these months.
Feeding ecology and food plan
Diet seems to consist virtually solely of copepods, and presumably different plankton. Observations and comparisons with different copepod eaters (sei and proper whales) counsel that C. marginata could use a surface-skimming method for feeding. As talked about, elevated sightings and strandings within the waters off the Cape Peninsula of South Africa from December to February have steered a seasonal inward migration throughout these months, which coincides with a rise within the biomass of zooplankton that happens through the Southern Hemisphere’s spring and summer season.
Little is thought about reproductive biology. The mating season, the mating system, the gestation interval, and the calving interval are all unknown. Some researchers imagine that calving could happen year-round. Newborns are round 6.5 ft (2 m) and attain 9-11.5 ft (3.0-3.5 m) at weaning. S*xual maturity is reached at 16-20 ft (5-6 m).
Caperea marginata is now listed on appendix I of the CITES, which means it's thought of “Threatened, though it is not listed by the IUCN.” Though it's the solely baleen whale to escape large-scale business whaling, it's thought to be comparatively uncommon. It could also be in danger due to the issue of distinguishing it from the Antarctic minke whale ( B. bonaerensis), 440 of which the Japanese harvested yearly within the Southern Ocean. The International Whaling Commission has estimated inhabitants measurement due to lack of knowledge. Caperea marginata is assumed to be threatened by world local weather change, however not by poisonous contamination.
Significance to people
Though C. marginata have by no means been caught commercially, people have been caught intentionally by inshore fisheries, and by accident in fishing nets.