geografia: Narwhal

Evidence: 100 • authority: 72

The narwhal (Monodon monoceros) is a species of toothed whale native to the Arctic. It is the only member of the genus Monodon and one of two living representatives of the family Monodontidae. The narwhal is a stocky cetacean with a relatively blunt snout, a large melon, and a shallow ridge in place of a dorsal fin. Males of this species have a spiralled tusk, which is a protruding left canine, that is 1.5–3.0 m (4.9–9.8 ft) long and thought to function as a secondary sexual characteristic, a weapon, a tool for feeding, or a sensory organ. Specially adapted slow-twitch muscles, along with the jointed neck vertebrae and shallow dorsal ridge allow for easy movement through the Arctic environm…

Evidence: 45 • authority: 92

Stroke rate detection from accelerometer data on marine mammals.. Overall dynamic body acceleration (ODBA) is widely used as a proxy for movement activity. However, for large, slow-moving animals such as cetaceans, ODBA is dominated by orientational shifts rather than dynamic movements. We argue for using stroke rate frequency as an alternative to ODBA and present a method for estimating stroke rate from acceleration data, using narwhals as a case study. The resulting stroke rates aligned with diving phases and depths, where gliding is expected to be prevalent. The results were also competitive with state-of-the-art magnetometer-assisted approaches. The method also successfully detected ind…

Evidence: 41 • authority: 72

The physiology of underwater diving is the physiological adaptations to diving of air-breathing vertebrates that have returned to the ocean from terrestrial lineages. They are a diverse group that include sea snakes, sea turtles, the marine iguana, saltwater crocodiles, penguins, pinnipeds, cetaceans, sea otters, manatees and dugongs. All known diving vertebrates dive to feed, and the extent of the diving in terms of depth and duration are influenced by feeding strategies, but also, in some cases, with predator avoidance. Diving behaviour is inextricably linked with the physiological adaptations for diving and often the behaviour leads to an investigation of the physiology that makes the be…

Evidence: — • authority: 88

Some characteristics of narwhal,<i>Monodon monoceros</i>, diving behaviour in Baffin Bay. Dive data were collected from nine narwhals, Monodon monoceros, instrumented with satellite-linked dive recorders in northwest Greenland in August–September 1993 and 1994. Data were collected for periods ranging from a few weeks to 9 months. The narwhals made daily dives to depths of more than 500 m and frequently dived to 1000 m or more. However, most of the time spent below the surface was in the water column at depths of between 8 and 52 m. For two males that were tracked from September through November the maximum dive depth increased steadily through time. There were no consistent differences in t…

Evidence: — • authority: 92

Behavioural analysis of multi-year satellite telemetry data provides insight into narwhal (Monodon monoceros) winter prey selection in Baffin Bay.. Narwhals (Monodon monoceros) are deep-diving Arctic cetaceans that migrate seasonally between summering and wintering grounds. The Baffin Bay population overwinters in southern Baffin Bay and Davis Strait, where they are known to forage on high-energy benthic prey. Studying narwhal winter behaviour and prey preference has been challenged by their remote distribution and limited lifespan of satellite tags deployed in summer, restricting data on their habitat use and foraging strategies. Since prey consumption is thought to peak in the winter, und…