Whale of the Month - Northern Bottlenose Whale
Species fact file
Common names: northern bottlenose whale
Icelandic name: andarnefja
Scientific name: Hyperoodon ampullatus
Family: Ziphiidae (beaked whales)
Max length: 9.8m (males), 8.5m (females)
Distribution: North Atlantic Ocean
The northern bottlenose whale is the largest beaked whale in the North Atlantic. Beaked whales are some of the most elusive cetaceans and as such these species can be very difficult to research. But northern bottlenose whales were previously hunted throughout the Atlantic, and have been relatively well-studied due to the availability of specimens from whaling. In addition to this, they are an inquisitive species and regularly approach boats.
Bottlenose whales have a very distinctive protruding round melon and short beak. Males are slightly larger than females, and there are also some differences in the shape and colour of the melon which can help to identify the sex. Males have larger and much steeper foreheads, so that their melon appears almost square, which lighten with age.
As is characteristic of beaked whales, only the males have teeth: one pair of small, conical teeth protrude forwards from the tip of the bottom jaw. Their remaining teeth (and all pairs of teeth for females) stay buried in the gums for their whole life.
This singular pair of teeth are not used for hunting or feeding. Most male beaked whales use their teeth while fighting other males in competitions for mates. The northern bottlenose whale is unusual in this respect, as they do not use their teeth while fighting – instead, they use their large melons to head-butt or ram one another.
Northern bottlenose whales primarily eat deep-water squids, but they may also feed on some bottom-dwelling fish species and invertebrates. Since their food live at the bottom of the ocean, these whales live away from the shallow coasts in areas which are very deep. Like all beaked whales, they are expert deep divers, and hunt near the seafloor at depths of over 800m – sometimes as deep as 1,400m. Northern bottlenose whales are capable of making dives two hours or more, but they are normally less.
Although we have more information on northern bottlenose whales compared to most other beaked whales, behavioural studies are still rare. Most of our knowledge in this respect comes from a deep-water canyon system in Nova Scotia, which a relatively small and isolated population of northern bottlenose whales inhabit. Here, photo identification – using photographs of the dorsal fin to identify and individual whale – can be used successfully to assess this population’s size and how it changes over time, seasonal movements within the region, and its social structure.
These northern bottlenose whales form small social units, normally consisting of less than 10 individuals, but occasionally aggregate in groups up to 50. Despite being deep divers, with similar prey to sperm whales, northern bottlenose whales appear to have a very different social structure. Their social groups are much more similar to those of typically shallow-feeding bottlenose dolphins. Females have loose networks with other females and juveniles, and do not appear to form particularly strong or long-term social bonds. On the other hand, males do form strong associations, but only with other males.
In Icelandic waters research is carried out on bottlenose whales using the same photo ID technique, as well as acoustic monitoring. However, in Iceland and the northeastern Atlantic as a whole, obtaining reliable estimates of population size has proven challenging.
In 1995, there was extensive, in-depth research into the population of northern bottlenose whales in the Northeast Atlantic. This project used a wealth of data from many different sources. Unfortunately, the results were inconclusive: estimating the pre-whaling population as anywhere between 35,000 and 110,000 whales, and the current population as either recovered or still greatly reduced in the aftermath of commercial whaling.
The species as a whole is classed as near-threatened, but the IUCN considers the status of northern bottlenose whales in European waters to be data-deficient. Current research being carried out in Iceland will help to fill in the gaps in current scientific knowledge, and provide much-needed data for the conservation of this mysterious and enigmatic whale.
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The social structure of northern bottlenose whales