Antarctic bottlenose whale, Flatheaded bottlenose whale, Southern bottle-nosed whale
The southern bottlenose whale (Hyperoodon planifrons ) is a species of whale, in the Ziphiid family, one of two members of the genus Hyperoodon. Seldom observed, the southern bottlenose whale is resident in Antarctic waters. The species was first described by English zoologist William Henry Flower in 1882, based on a water-worn skull from Lewis Island, in the Dampier Archipelago, Western Australia. They live in deep ocean waters over 1000 meters.
The Southern bottlenose whale has a sturdy built and a rather unusual appearance. The species is so called due to its short, tube-like beak and a large, bulb-like forehead. These animals exhibit a head crest, which has a rounded shape in females and juveniles. Head crest of males usually becomes larger and heavier as they age, changing the shape of their forehead. Older males display a flat and squared-off head crest. There's no information on purpose of the enlargement of their forehead, although adult males are likely to use it in their fights, head-butting their opponents. The lower jaw of males holds 2 front teeth. The color of their skin ranges from chocolate-brown to yellow. Meanwhile, the flanks and under parts of these whales have lighter coloration, because of photosynthetic algae, which lives on their skin. Females of this species live more than 37 years, whereas lifespan of males is more than 50 years.
The Southern bottlenose whales are distributed throughout circumpolar area of the southern Ocean. They are likely to be migratory, travelling from the Antarctic northwards to temperate waters at the end of summer, reaching as far as South Africa, Brazil and Western Australia. The Southern bottlenose whales inhabit deep oceanic waters of more than 1,000 meters, and don't tend to occur in waters shallower than 200 meters. In summer, they can be seen within 100 km of the edge of the Antarctic ice.
Southern bottlenose whales are sociable animals, forming small groups called herd, consisting of 2 - 12 individuals. Members of a group travel and dive together. They typically dive under ice and then surface, sticking their beaks out of the water before sounding. These whales socialize only with conspecifics and do not tend to communicate with other species. When coming up to breathe, they remain at the surface for up to 10 minutes before taking a long dive. These whales release air from their blowhole very often, approximately every 30 seconds. When threatened, they can swim very fast, raising their heads completely out of the water as they surface. Breaching and porpoising are common behaviors in this species, though they do it away from boats and generally avoid any vessels.
The Southern bottlenose whales are carnivores (molluscivores). The diet of these whales mainly consists of squid, complemented with various species of fish.
Little is known about the reproductive behavior and habits of this species. Southern bottlenose whales probably mate during summer months, while births occur during the following spring - early summer. As beaked whales, these animals may breed once every few years, yielding a single baby, which is sexually mature at 11 years old.
Along with other beaked whales, these animals suffer from loud human-made sounds, produced by naval sonar and seismic exploration: these sounds are extremely dangerous for whales and can subsequently lead to gas bubble disease. On the other hand, they may be threatened by climate change, causing increase in sea level and surface temperature. However, there is no information on how exactly these changes can affect the local population of Southern bottlenose whales. Other notable concerns include pollution, due to which toxic substances accumulate in body tissues of whales. Southern bottlenose whales are often incidentally caught in driftnet fisheries and discarded. In addition, they compete for food with squid fisheries at lower latitudes of their oceanic range.
According to IUCN, the Southern bottlenose whale is abundant and the most common species throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.
