Northern Bottlenose Whale
Common Names: Northern bottlenose whale
Irish Name: An míol mór bolgshrónach
Key Identification Features
Maximum body length: Adult male 9.8m (33ft), adult female c8.6m (28ft)
Average body length: Adult 7-9m (23 to 29.5ft}
Blow: Bushy blow, every 30-40sec when at surface, 1-2m high, only visible in calm conditions.
Head and beak: The head is the dominant feature of this species; in females and young, it is rounded but not particularly defined from the beak. In males, however, the front surface is flat and it overhangs the beak, becoming more and more buff as they age. The bottle-like beak is moderately long.
Teeth: There are two teeth on the lower jaw on males only, and sometimes another pair can be found just behind these.
Dorsal fin: Slightly falcate or triangular shape, pointed tip, may be darker than rest of back.
Fluke: Broad flukes with concave trailing edges, no caudal notch on fluke.
Colouration: The dorsal surface being dark grey to brown and a grayish white ventral surface, forehead and beak. The skin can appear to have a mottled appearance, and in old males, the facial regions can turn white.
Markings: Lighter band around neck on some animals, body often scratched and scared
The Northern bottlenose whale is the only beaked whale in the North Atlantic with a large bulging melon, and should be easy to identify. They occasionally raise their tail flukes when diving; are curious and often approach boats.
Species Similar in Appearance
Females and young males can be confused with smaller beaked whales such as Cuvier's and Sowerby's. If only seen from behind, they could be confused with the minke whale.
Northern bottlenose whales travel in groups of four to ten. They are extremely curious and will often investigate stationary boats for lengthy periods. Mixed herds seem to occur early in the spring, including newborn calves, while in autumn, solitary males are common. Care giving (epimeletic) behaviour is known for the bottlenose whale. They do not leave a wounded companion until it dies.
- Spy hopping: Thrusting of head clear out of water to look around
- Breaching: Frequently logged
- Fluke slapping: Fluke rarely leaves water.
Status and Distribution
Northern bottlenose whales are widely distributed in the North Atlantic, but seem to avoid shallow waters such as the continental shelf. They are found from Nova Scotia to parts of the Davis Strait, along the east coast of Greenland, around Iceland, Ireland and up to the west coast of Norway.
The winter distribution is poorly known, but they probably stay in the lower latitudes of the North Atlantic, although there are reports of sightings in south western Europe in winter. Population unknown but listed as vulnerable since 1976.
Where and When Best Seen in Ireland
The migrations of northern bottlenose whales are little known, although it appears that they migrate northwards to sub-arctic regions in spring and southwards in the early autumn. The number of bottlenose whales stranded in the UK and Irish coasts seem to increase in the autumn, possibly due to a southward migration at that time of year. Rarely sighted off the Irish coast, more commonly seen in deeper waters beyond continental shelf
Food and Feeding
Squid form the bulk of their diet, but fish and invertebrates such as deep- sea prawns are also eaten. The amount of fish consumed seems to vary between regions. Herring has been found in large amounts in the stomachs of individuals.
Bottlenose whales probably feed near the sea bed, since benthic animals such as starfish and sea cucumbers have been found in some animal's stomachs, as well as stones, shells, clay and bits of wood. It has been suggested they may sometimes use the beak as a plough in the mud when foraging.
Reproduction and Life Cycle
Female bottlenose whales attain sexual maturity at a mean length of about 6.9 m and usually at 8 to 12 years of age (although some may not mature until about 18 years of age). Males become sexually mature at a mean length of 7.5 m and about 11 years of age. The gestation period is estimated to be about 12 months. The peak of mating and births is in April. Lactation is estimated to last at least 1 year, although observations of female whales accompanied simultaneously by newborn calves and juvenile animals, suggest that lactation may be prolonged. The calving interval is estimated to be 2 years.
Beginning in the late 19th century, the northern bottlenose whale was intensively hunted by Norway. The species has been protected by the IWC since 1977. Their population is falling but there is disagreement on the extent of this. They were listed as "vulnerable", although they are still locally abundant in some areas. There are concerns however, that human activities, such as shipping, oil/gas surveys and production, close to their core habitat may affect northern bottlenose whales, who produce social sounds that are of very low amplitude of 30khz and so may be affected by noise from shipping traffic and seismic vessels. In common with other deep diving whales, they may also be vulnerable to ship strikes, due to the long "surface time" needed to recover from deep dives.