Hyperoodon ampullatus, Forster, 1770

Russell A. Mittermeier & Don E. Wilson, 2014, Ziphiidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 326-357 : 348-349

4.

Northern Bottlenose Whale

Hyperoodon ampullatus

French: Baleine-a-bec boréale / German: Nordlicher Entenwal / Spanish: Zifio calderén septentrional

Other common names: Bottlehead, Bottlie, Common Bottlenose Whale, Flounder's Head, North Atlantic Bottlenose Whale

Taxonomy. Balaena ampullatus Forster, 1770 ,

Maldon (England).

Forster named this species based on descriptions of whales seen at sea by P. Kalm during his travels in North America and on the description written by T. Pennant in 1769 of S. Dale’s “beaked whale” which was found stranded in Maldon, Essex, United Kingdom,as long ago as September 1717. Monotypic.

Distribution. Restricted to the cooler waters of the N Atlantic Ocean, as far N as the Davis Strait, Jan Mayen, and Spitsbergen, and as far S as NE USA, Azores, and Canary Is; in E Atlantic Ocean, this species appears to be relatively rare S of Bay of Biscay. Although its occurrence seems to be relatively continuous in some parts of its distribution, such as in the E Atlantic Ocean, it appears to be more fragment ed in others, such as in the waters off E Canada.

Descriptive notes. Total length 600-1000 cm; weight 7500-10,000 kg. The Northern Bottlenose Whale is the only beaked whale where there is evidence that adult males are consistently larger than adult females. Body is spindle-shaped, with greatest girth around its midpoint. Flukes are wide in relation to body length, and tailstock is compressed laterally. Dorsal fin is small and set approximately two-thirds the distance between tip of the beak and end of the tail. Coloration is typically dark brown, dark gray, or black. Unlike many other species of beaked whales, Northern Bottlenose Whales, even older males, do not accumulate white linear scars resulting from intraspecific aggression. Rostrum and lower jaw form a short but well-defined beak, and there are two grooves on the throat. Shape of forehead is notably sexual dimorphic. In young males and females, forehead is rounded and similar to that of the bottlenose dolphins (7ursiops spp.). As males mature, forehead becomes enlarged and flattened due to growth of bony crests on maxillary bones of the skull. When fully mature, heads of adult males can rise almost vertically from the beak. With maturity, pigmentation of skin on the front of the forehead may become reduced until it becomes a pale white in the oldest males. Unlike many other species of beaked whales, adult males have no functional teeth and lack tusks that are one of the most distinctive features of the family Ziphiidae .

Habitat. Deep oceanic waters and generally in areas where water depths are greater than 500 m. Northern Bottlenose Whales appear to favor areas with complex seabed topography and are most commonly recorded in canyons along shelf margins, around oceanic islands, or around seamounts. Northern Bottlenose Whales may be yearround residents in some locations. In others, there is evidence of large-scale seasonal movements. In particular, a large number of individuals seem to move into the Norwegian Sea in early spring and summer and move out again in late summer and early autumn. Its not known where these individuals go, but seasonal patterns of strandings around the Faroe Islands, UK, and the Republic of Ireland suggest that they may move through the Faroe-Shetland channel and into the Atlantic Frontier region to the west of the British Isles. During these movements, it is not uncommon for some individual Northern Bottlenose Whales to stray into shallower shelf waters, where they may remain for extended periods of time before either leaving or stranding.

Food and Feeding. Primary prey of the Northern Bottlenose Whale throughout most of its distribution is the squid Gonatusfabricii, but they consume a wide range ofspecies of deep-water squid, and deep-water fish are not uncommon in the diet in some locations. They primarily consume a very narrow range of prey sizes. Most prey is 0-5-6% of an individual whale’s total body length. Prey capture is almost certainly achieved through suction feeding. Information from dive tags suggests that most foraging of Northern Bottlenose Whales occurs at or near the seabed and that they spend ¢.67% of theirlife at water depths greater than 1000 m. Individual dives are commonly longer than 30 minutes and may last more than an hour.

Breeding. Northern Bottlenose Whales become sexually mature at a body length of ¢.600 cm for females and c.730 cm for males when they are 7-8 years old. Gestation lasts for ¢.12 months, and a single offspring is born at a length of ¢.300-350 cm. Weaning is thought to occur after one year, and there may be a minimum of two years between births. Nothing is known of the courtship behavior of Northern Bottlenose Whales, but it appears that males engage in aggressive interactions that involve head butting, and this may be the function of the large maxillary crests found in adult males. Males also appear to form long-term alliances, but it is not known how this relates to mating. Northern Bottlenose Whales maylive as long as 37 years, with males possibly living longer than females.

Activity patterns. There is no specific information available for this species, but the majority of their time is spent foraging at depths greater than 500 m.

Movements, Home range and Social organization. Some populations of Northern Bottlenose Whales, such as the one found in and around the Gully (a submarine canyon off the east coast of Nova Scotia, Canada), are known to be resident, but there is evidence of large-scale seasonal movements in other areas, such as the Norwegian Sea. Movements of individuals have only been studied in the population found in the Gully. Individuals studied remain resident in this area for extended periods of time; however, it is not known how representative this population is of the species as a whole. Northern Bottlenose Whales usually occur in small groups of 1-4 individuals, with a maximum group size of¢.20 individuals. Studies ofthe social organization of the Gully population suggest that it has a social system similar to that of some populations of Common Bottlenose Dolphin ( Tursiops truncatus ), where males form long-term stable alliances and females form loose and more fluid associations. Nevertheless, it is not known how representative thisis of the species as a whole. Evidence from whaling suggests that a tight social bond can exist among individuals in a single group, with other whales coming to the aid of a harpooned individual.

Status and Conservation. CITES Appendix I. Classified as Data Deficient on The IUCN Red List. There are no estimates of global population size of Northern Bottlenose Whales, although estimates are available from some regions. A population of ¢.40,000 individuals has been estimated for the eastern North Atlantic as a whole, with estimates ofjust over 3000 individuals for Icelandic waters and just under 300 for Faroese waters.

However,it is not clear how reliable these estimates are due to difficulties associated with conducting surveys for deep-diving species that spend prolonged periods of time below the surface. An isolated population of ¢.160 individuals is known to occur around the Gully off Nova Scotia. Commercial whalers hunted Northern Bottlenose Whales, and more than 65,000 were killed between the mid-1800s when they were first targeted and 1977 when whaling for this species was banned. By then, the global population may have been as low as 30% ofits pre-whaling size. It is now estimated to have rebounded to ¢.60% of that size, but it is thought that many subpopulations are still depleted. Small numbers of Northern Bottlenose Whales are still killed in traditional drive fisheries in the Faroe Islands from time to time. Although whaling was the main conservation issue for Northern Bottlenose Whales in the past, at present other known or potential impacts are of more concern. These include damage to deep-water ecosystems from fishing and noise pollution from shipping and military activities. Impacts of such activities on oceanic species are difficult to study and quantify, and it is not currently known how great a threat they are to Northern Bottlenose Whales as a species or to individual populations or subpopulations within their distribution. As a species restricted to cooler waters, Northern Bottlenose Whales may also be at risk from effects of climate change. Nevertheless, nothing is known about the form or extent of these potential impacts.

Bibliography. Gowans & Rendell (1999), Gowans et al. (2001), Hooker, Whitehead & Gowans (1999), Hooker, Whitehead, Gowans & Baird (2002), MacLeod (2006, 2009), MacLeod & D'Amico (2006), Macleod, Perrin et al. (2006), MacLeod, Pierce & Santos (2004), MacLeod, Santos & Pierce (2003), Mead (1989a), Rice (1998).

Figures

1. Baird’s Beaked Whale (Berardius baiwrdu), 2. Arnoux’s Beaked Whale (Berardius arnuxu), 3. Cuvier’s Beaked Whale (Ziphius cavirostris), 4. Northern Bottlenose Whale (Hyperoodon ampullatus), 5. Southern Bottlenose Whale (Hyperoodon planifrons), 6. Shepherd’s Beaked Whale (Tasmacetus shepherd), 7. Longman’s Beaked Whale (Indopacetus pacificus), 8. Hubbs’s Beaked Whale (Mesoplodon carlhubbsi), 9. Stejneger’s Beaked Whale (Mesoplodon stejnegeri), 10. Pygmy Beaked Whale (Mesoplodon peruvianus), 11. Perrin’s Beaked Whale (Mesoplodon perrini), 12. True’s Beaked Whale (Mesoplodon marus), 13. Strap-toothed Whale (Mesoplodon layardii), 14. Hector’s Beaked Whale (Mesoplodon hectori)

Distribution. Restricted to the cooler waters of the N Atlantic Ocean, as far N as the Davis Strait, Jan Mayen, and Spitsbergen, and as far S as NE USA, Azores, and Canary Is; in E Atlantic Ocean, this species appears to be relatively rare S of Bay of Biscay. Although its occurrence seems to be relatively continuous in some parts of its distribution, such as in the E Atlantic Ocean, it appears to be more fragment ed in others, such as in the waters off E Canada.