Northern bottlenose whale

Description

When physically mature, northern bottlenose whales can reach 9.8 metres (32 ft) in length, smaller than giant beaked whales, and larger than known records of southern bottlenose whales. Their foreheads, or melons are sexually dimorphic, so that mature males have larger melons, which are flattened or square shape, while mature females and juveniles have rounder melons. Melon coloration can vary, though it appears the head of most males becomes more white or buff colored with age. The beak is not as long as other beaked whale species, and only mature males have two small teeth, which erupt at the front end of the bottom jaw, but are not easily seen. Females also have teeth, but they are buried in the jaw and do not erupt. The dorsal fin is relatively small, at 30–38 centimetres (12–15 in) and about two thirds of the way back on their bodies. It is falcate (sickle-shaped) and usually pointed. The back is mid-to-dark grey with a lighter underside. They weigh approximately 5,800–7,500 kilograms (12,790–16,530 lb). Females generally live around 27 years, whereas males can live to be 37. Males typically become sexually mature at around the age of 9 and females at the age of 10.

Behaviours

Unlike many species of beaked whale, northern bottlenose whales are known to approach and appear curious about vessels, which made them relatively easy targets for whale hunters. However they have demonstrated avoidance to certain sounds such as those emitted by naval sonar in controlled dose response studies. 
Underwater recordings have found that northern bottlenose whales produce regular high frequency clicks in click trains, which have a characteristic frequency modulated pulse or "upsweep", commonly found in other species of beaked whales.
According to sources, it is highly possible that in between longer and deeper dives bottlenose whales have shorter and shallower dives in order to prevent decompression sickness. In between dives, these whales often socialize at the surface in groups of 4 to 20.

Reproduction

Mating behavior is mostly observed from spring to early summer. The female will carry the offspring for a year. For northern bottlenose whales off of the Scotian shelf the main calving period occurs in late summer.  It is widely believed that bottlenose whales are polygynous.

Feeding

Northern bottlenose feed mainly on deep water squid, primarily Gonatus fabricii or Gonatus steenstrupi, and bottom fish, such as Greenland halibut. Foraging dives can last an hour or more at depths reaching 1000 meters. A small percentage of northern bottlenose whales have been also been observed hunting for smaller animals off the coast of Iceland in between meals. These are including but not limited to redfish, rabbitfish, spiny dogfish, and skate.

Population and distribution

The northern bottlenose whale is endemic to the North Atlantic Ocean and populations are found in the deep (>500 m) cold subarctic waters of the Davis Strait, the Labrador Sea, the Greenland Sea and the Barents Sea, but can range as far south as Newfoundland and Nova Scotia. As of 2017, the population in the North East Atlantic is estimated to be between 10,000 and 45,000.    
"The Gully", a large submarine canyon east of Nova Scotia, is the home of the "Scotian Shelf" population of 164 whales, currently listed under Canada's Species at Risk Act as endangered. This population is the focus of a long-term research project conducted by the Whitehead Lab, at Dalhousie University since 1988. According to recent studies, bottlenose whales living in the Scotian Shelf contain higher levels of DDT than the population of whales living near the Davis Strait. 
It was widely speculated that there were two separate groups of northern bottlenose whales found in Greenland, each with separate morphology and behavior. Because there is no evidence to prove this, it was decided in 1976 by the Scientific Committee of the International Whaling Commission that only one population existed. Since 2011 it has been determined that two populations off the Scotian Shelf are genetically distinct from each other. There is evidence in different morphology in both juveniles and adults, from melon size to coloring with age.   
On 20 January 2006, a northern bottlenose whale was spotted in Central London in the River Thames. The River Thames whale reached as far up river as Albert Bridge. It was moved onto a barge and rescuers hoped to take it out to sea, but it died following a convulsion on 21 January during its rescue. Its skeleton is now in the Natural History Museum in London. 

There was another sighting on 6 August 2019 at Loch Linnhe, a sea loch located off the West coast of Scotland.  At the time it was thought to be searching for food in the area. There have been 21 previous live sightings of the northern bottlenose whale in Scotland since 2000. It is speculated that these whales may migrate to north west European shelf waters in the summertime.

History of discovery

It was first described by Johann Reinhold Forster in 1770, basing the name on the "bottle-nosed whales" seen by Pehr Kalm in his Travels into North America, and on Thomas Pennant's 1766 description of Samuel Dale's "bottle-head whale" found stranded above a bridge in Maldon, Essex, in 1717.

Conservation

Prior to the beginning of whaling, it is estimated that there were upwards of 100,000 northern bottlenose whales in the North Atlantic. Between 1850 and 1973, commercial hunting of the species, focused on populations found off Norway, Iceland, Greenland and Labrador, greatly reduced their numbers across their range. Current conservation concerns include threats from human activities such as disturbance related to offshore oil and gas developments and naval sonar, as well as entanglement, pollution, ingestion of plastic and ecosystem shifts related to climate change.
The International Whaling Commission designated the northern bottlenose whale as a protected stock in 1977 and set a zero catch quota. Northern bottlenose whales are still killed in the Faroe Islands. Faroese regulations only allow the killing of bottlenose whales which have beached themselves and cannot be driven out again. Long term statistics indicate that the most frequent beachings are in the villages of Hvalba and Sandvík on Suðuroy.
The northern bottlenose whale is listed under Canada's Species at Risk Act as endangered, as data deficient under the IUCN red list and on Appendix II  of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). In addition, the northern bottlenose whale is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS).
Unfortunately, due to this species’ low genetic diversity and low reproductive rate, recovery of the population may provide a challenge to researchers and conservationists.