Post by OldGreenVulture on Dec 3, 2019 12:54:43 GMT
Northern Bottlenose Whale - Hyperoodon ampullatus.
Scientific classification
Class: Mammalia
Order: Cetacea
Family: Ziphiidae
Subfamily: Hyperoodontinae
Genus: Hyperoodon
Species: Hyperoodon ampullatus
Description
Northern bottlenose whales are the largest beaked whales in the North Atlantic and reach 10 m (and possibly up to 11.2 m) body length. Their body mass can reach 7,500 kg (Jefferson et al. 2008). Body shape is robust and they have a large, bulb-shaped forehead and short, dolphin-like beak. Their colour is chocolate brown to yellowish-brown, being lighter on the flanks and belly. Some of this colouration is believed to be caused by a thin layer of diatoms. Mature males have a squared-off forehead, which turns white after sexual maturity is reached, whereas in females and immature males it is rounded and brown (Bloch et al. 1996). Older females have a white band around the neck (Jefferson et al. 2008). Males possess a single pair of conical teeth at the tip of the lower jaw, rarely visible in live animals, especially if the mouth is closed (Gowans, 2002).
Distribution
The North Atlantic bottlenose whale is found in the subarctic North Atlantic from Davis Strait, Jan Mayen, west coast of Spitsbergen, and Bjornøya, south to Nova Scotia and the western side of the British Isles (Rice, 1998).
In the eastern part of their distributional range, there are no confirmed records from Novaya Zemlya, the Barents Sea or the coast of Finnmarken in northern Norway (Mead, 1989). There are few records east of the Norwegian Sea and from the Mediterranean (Rice, 1998). One specimen was reportedly caught in the North Sea during the period 1938-1972 and Kastelein and Gerritis (1991) observed an animal off The Netherlands, however the shallow southern North Sea may not be part of its native range. Strandings are reported from the coasts of Belgium, The Netherlands, Denmark, France and England (Boschma, 1950; De Smet, 1974; Duguy 1990, Van Gompel 1991, Kinze et al, 1998). Lick and Piatkowski (1998) report on a stranding in the southern Baltic Sea. Gowans (2002) also includes the Azores into the range of the species.
Distribution of Hyperoodon ampullatus: North Atlantic Ocean, normally in water deeper than 1,000m
In the western North Atlantic, Lucas and Hooker (2000) report recent strandings from Sable Island, Nova Scotia and further strandings have been reported from as far south as Rhode Island (Mead, 1989; Reyes, 1991).
Past reports of H. ampullatus in the temperate and subarctic North Pacific seem to have been due to confusion with Berardius bairdii, because both species are known colloquially as "bottle-nose whales" (Rice, 1998).
Population size
Stocks: There seem to be certain pockets of abundance, for example: around "the Gully", between Sable Island and Nova Scotia; in the Arctic Ocean, between Iceland and Jan Mayen, southwest of Svalbard and east off Iceland-north off the Faroes; and in Davis Strait, off northern Labrador, especially around the entrance to Hudson Strait and Frobisher Bay (Carwardine, 1995).
For statistical consideration Christensen (1976) assumed that all the bottlenose whales caught east of Greenland belonged to a single population, while Mitchell (1977) defined Cape Farewell (Greenland) to divide west and east North Atlantic catches. Recently some limited evidence for stock structure is emerging. Animals in The Gully, off Nova Scotia seem to be largely or totally distinct from the population off northern Labrador: they are smaller and appear to breed at a different time of year (Whitehead et al. 1997). Gowans (2009) suggests that different length distributions in whales found in different areas of the Atlantic indicates possible geographical isolation. Furthermore, genetic studies indicate reproductive isolation between bottlenose whales in the Gully and Labrador, the latter seem to be more related to their conspecifics from Iceland (Dalebout et al. 2006).
Population size: The total number of northern bottlenose whales off the eastern U.S. coast is unknown (NEFSC 2007) and this holds true for most of their range. Barlow et al. (2006) list the reasons: mostly unknown population structure, a knowledge gap with respect to distribution, difficulties in estimating correction factors for missed animals due to long dive times and a lack of dedicated surveys.
Whitehead et al. (1997) estimate that approximately 230 H. ampullatus use the Gully, a prominent submarine canyon on the edge of the Nova Scotia Shelf, throughout the year. Approximately 57% of the population reside in a 20 x 8 km core area at the entrance of the canyon at any time. Gowans et al. (2000) analysed data from 11 years of photo-identification records to estimate the population size using mark-recapture techniques and found no significant change in population size over time. Sex ratio was roughly 1:1, with equal numbers of sub-adult and mature males. The population was recently estimated to contain about 163 animals (95% confidence interval 119-214), with no statistically significant temporal trend (Whitehead and Wimmer, 2005).
Estimates for Icelandic and Faroese waters are 3,142 and 287 whales respectively, although allowance was not made in the analysis for animals not observed because of their long dives (Reyes, 1991). Gunnlaugsson and Sigurjonsson (1990) estimate 5,827 whales at high latitudes in the Northeastern Atlantic and NAMMCO has calculated the population size of this species in the eastern part of the North Atlantic to be around 40,000 individuals (NAMMCO Annual Report 1995).
A study by Christensen and Ugland (1984) resulted in an estimated initial (pre-whaling) population size of about 90,000 whales, reduced to some 30,000 by 1914. The population size by the mid-1980's was said to be about 54,000, nearly 60% of the initial stock size.
Habitat
H. ampullatus is most common beyond the continental shelf and over submarine canyons, in deep water (>1,000m). It sometimes travels several kilometres into broken ice fields, but it is more common in open water. Few whales were caught over the continental shelf off Labrador and in waters less than 1,000m deep off the west coast of Norway. In the surrounding waters of Iceland, the whales were sighted at surface temperatures between -1.3°C and +0.9°C (Reyes, 1991).
Behaviour
The northern bottlenose whale is a curious animal: it will approach stationary boats and seems to be attracted by unfamiliar noises, such as those made by ships' generators. This, combined with its habit of staying with wounded companions, made it especially vulnerable to whalers. These deep divers can remain submerged for an hour, possibly as long as 2 h (Reeves et al. 1993, Bloch et al. 1996). Hooker and Baird (1999) showed that northern bottlenose whales in a submarine canyon off Nova Scotia exhibit an exceptional diving ability, with dives approximately every 80 min to over 800 m (maximum 1,453 m) depth, and up to 70 min in duration. Sonar traces of non-tagged, diving bottlenose whales in 1996 and 1997 suggest that such deep dives are not unusual. This shows that they may make greater use of deep portions of the water column than any other mammal so far studied. Many of the recorded dives of the tagged animals were to, or close to, the sea floor, consistent with benthic or bathypelagic foraging.
Reproduction
Northern bottlenose whales have a peak in calving in April (Jefferson et al. 1993).
Schooling
Most pods contain at least 4 whales, sometimes with as many as 20, and there is some segregation by age and sex (Mead, 1989, Jefferson et al. 1993). Northern bottlenose whales in the Gully also form small groups. Associations within age/sex classes (female /immature, subadult male and mature male) were significantly higher than associations between different classes. Females and immature bottlenose whales formed a loose network of associations, showing no preferential associations with particular individuals or those from specific age/sex classes nor any long-term bonds. Mature and subadult males had stronger associations with individuals in their own class, and associations between some males lasted for several years, although males also formed many short-term associations. Overall the social organization of northern bottlenose whales in the Gully appears to resemble that of some bottlenose dolphins, Tursiops truncatus, living in shallow, enclosed bays (Gowans et al. 2001).
Food
Although primarily adapted to feeding on squid, these whales also eat fish, sea cucumbers, starfish, and prawns. They apparently do much of their feeding on or near the bottom (Jefferson et al. 1993; Mead, 1989). Hooker et al. (2001) found a high proportion of the squid Gonatus steenstrupi in the stomachs of two bottlenose whales stranded in eastern Canada. They also collected remote biopsy samples from free-ranging bottlenose whales off Nova Scotia and determined fatty acid composition. Overall, the results of these techniques concurred in suggesting that squid of the genus Gonatus may form a major part of the diet of bottlenose whales in the Gully (Hooker et al. 2001).
Stomach content analysis by Clarke and Kristensen (1980) on a specimen stranded on the Faroe Islands showed that while the cephalopods found included six cold water species which were probably taken in deep water within the vicinity of the Faroes, they also included one species, Vampyroteuthis infernalis, which is a warmer water species and probably ranges little further north than 40°N. This suggests the whale had been much further south in the Atlantic than the Faroes at 62°N just before its stranding or that the distribution pattern of this cephalopod is not that well known. The stomach contents examined in the Faroese show more diversity with 13 species eaten than those from a whale stranded in Denmark (Clarke and Kristensen, 1980) and from whales shot off Labrador and Iceland, which contained only one species, Gonatus fabricii. Santos et al. (2001) report on stomach contents of bottlenose whales stranded in the North Sea. Their results are in agreement with those of previous authors in that cephalopods in general, and G. fabricii in particular, are the main prey of the northern bottlenose whale.
Migration
Migratory movements are poorly documented, as are stock relations among the animals found in apparently disjunct centres of spring and summer abundance (Reeves et al. 1993). In the eastern part of the range H. ampullatus probably moves north in spring and south in autumn; in the west, at least some animals are believed to overwinter at lower latitudes. There may also be some inshore-offshore movements (Carwardine, 1995).
In the western North Atlantic, bottlenose whales are present during much of the year in The Gully and in the Labrador Sea. Bottlenose whales in The Gully appear to be largely non-migratory, and this population of a few hundred whales might be vulnerable to the environmental degradation associated with nearby oil and gas production (Reeves et al. 1993). However, Gowans et al. (2000) found that over the summer field season, individuals emigrated from, and re-immigrated into the Gully, spending an average of 20 days within the Gully before leaving. Approximately 34% of the population was present in the Gully at any one time. Individuals of all age and sex classes displayed similar residency patterns although there were annual differences as individuals spent less time in the Gully in 1996 than in 1990 and 1997. Sighting rates were similar in all years with extensive fieldwork, indicating little variability in the number of whales in the Gully each summer.
Mitchell (1977) suggested that in the western North Atlantic, H. ampullatus may forage into the Northeast Channel and the Gulf of Maine in winter months.
A southward migration, better known in the eastern North Atlantic begins in July, when animals are moving south from the Norwegian Sea, and continues to September. The increase of strandings on the British coasts and on the North Sea coasts probably reflects part of this summer migration, which remains unknown in the northwest Atlantic. There is evidence from the distribution of catches that a northward migration occurs in the eastern North Atlantic in April-July (Reyes, 1991 and refs. therein). Bottlenose whales occur all year round in the Faroes, but with a distinct peak a fortnight around 1 September pointing at a very synchronized southernly migration route (Bloch et al. 1996).
This is further supported by MacLeod et al. (2004): Strandings of northern bottlenose whales on the coasts of the UK and the Republic of Ireland were lowest in April and highest in September. The number of strandings between months differed significantly from an even spread, with more strandings between July and October. Most strandings in late summer and autumn occurred on North Sea coasts and their stomach contents included the squid Gonatus fabricii, which is found only in more northern waters. This suggests that these whales may be migrating southward at this time of year.
Evidence of migratory movements of beaked whales in the Northeast Atlantic was obtained from an examination of historical strandings data from the United Kingdom and the Republic of Ireland, and from whaling records from the Faroes, Iceland and the Norwegian Sea. There is strong evidence to suggest that beaked whales, particularly northern bottlenose whales, undertake regular migrations, moving south-west in late summer and autumn and moving north-east in late winter and spring (MacLeod and Reid, 2003).
Threats
The main threats to the northern bottle-nosed whale are thought to be chemical and noise pollution, prey depletion, human disturbance, and hunting. This species has been hunted more than any of the other species of beaked whales. The extent to which populations of this species have been reduced by hunting is unclear, and the current status of the population is unknown.
From Carnivora.
carnivora.net/northern-bottlenose-whale-hyperoodon-ampullatus-t2777.html
Scientific classification
Class: Mammalia
Order: Cetacea
Family: Ziphiidae
Subfamily: Hyperoodontinae
Genus: Hyperoodon
Species: Hyperoodon ampullatus
Description
Northern bottlenose whales are the largest beaked whales in the North Atlantic and reach 10 m (and possibly up to 11.2 m) body length. Their body mass can reach 7,500 kg (Jefferson et al. 2008). Body shape is robust and they have a large, bulb-shaped forehead and short, dolphin-like beak. Their colour is chocolate brown to yellowish-brown, being lighter on the flanks and belly. Some of this colouration is believed to be caused by a thin layer of diatoms. Mature males have a squared-off forehead, which turns white after sexual maturity is reached, whereas in females and immature males it is rounded and brown (Bloch et al. 1996). Older females have a white band around the neck (Jefferson et al. 2008). Males possess a single pair of conical teeth at the tip of the lower jaw, rarely visible in live animals, especially if the mouth is closed (Gowans, 2002).
Distribution
The North Atlantic bottlenose whale is found in the subarctic North Atlantic from Davis Strait, Jan Mayen, west coast of Spitsbergen, and Bjornøya, south to Nova Scotia and the western side of the British Isles (Rice, 1998).
In the eastern part of their distributional range, there are no confirmed records from Novaya Zemlya, the Barents Sea or the coast of Finnmarken in northern Norway (Mead, 1989). There are few records east of the Norwegian Sea and from the Mediterranean (Rice, 1998). One specimen was reportedly caught in the North Sea during the period 1938-1972 and Kastelein and Gerritis (1991) observed an animal off The Netherlands, however the shallow southern North Sea may not be part of its native range. Strandings are reported from the coasts of Belgium, The Netherlands, Denmark, France and England (Boschma, 1950; De Smet, 1974; Duguy 1990, Van Gompel 1991, Kinze et al, 1998). Lick and Piatkowski (1998) report on a stranding in the southern Baltic Sea. Gowans (2002) also includes the Azores into the range of the species.
Distribution of Hyperoodon ampullatus: North Atlantic Ocean, normally in water deeper than 1,000m
In the western North Atlantic, Lucas and Hooker (2000) report recent strandings from Sable Island, Nova Scotia and further strandings have been reported from as far south as Rhode Island (Mead, 1989; Reyes, 1991).
Past reports of H. ampullatus in the temperate and subarctic North Pacific seem to have been due to confusion with Berardius bairdii, because both species are known colloquially as "bottle-nose whales" (Rice, 1998).
Population size
Stocks: There seem to be certain pockets of abundance, for example: around "the Gully", between Sable Island and Nova Scotia; in the Arctic Ocean, between Iceland and Jan Mayen, southwest of Svalbard and east off Iceland-north off the Faroes; and in Davis Strait, off northern Labrador, especially around the entrance to Hudson Strait and Frobisher Bay (Carwardine, 1995).
For statistical consideration Christensen (1976) assumed that all the bottlenose whales caught east of Greenland belonged to a single population, while Mitchell (1977) defined Cape Farewell (Greenland) to divide west and east North Atlantic catches. Recently some limited evidence for stock structure is emerging. Animals in The Gully, off Nova Scotia seem to be largely or totally distinct from the population off northern Labrador: they are smaller and appear to breed at a different time of year (Whitehead et al. 1997). Gowans (2009) suggests that different length distributions in whales found in different areas of the Atlantic indicates possible geographical isolation. Furthermore, genetic studies indicate reproductive isolation between bottlenose whales in the Gully and Labrador, the latter seem to be more related to their conspecifics from Iceland (Dalebout et al. 2006).
Population size: The total number of northern bottlenose whales off the eastern U.S. coast is unknown (NEFSC 2007) and this holds true for most of their range. Barlow et al. (2006) list the reasons: mostly unknown population structure, a knowledge gap with respect to distribution, difficulties in estimating correction factors for missed animals due to long dive times and a lack of dedicated surveys.
Whitehead et al. (1997) estimate that approximately 230 H. ampullatus use the Gully, a prominent submarine canyon on the edge of the Nova Scotia Shelf, throughout the year. Approximately 57% of the population reside in a 20 x 8 km core area at the entrance of the canyon at any time. Gowans et al. (2000) analysed data from 11 years of photo-identification records to estimate the population size using mark-recapture techniques and found no significant change in population size over time. Sex ratio was roughly 1:1, with equal numbers of sub-adult and mature males. The population was recently estimated to contain about 163 animals (95% confidence interval 119-214), with no statistically significant temporal trend (Whitehead and Wimmer, 2005).
Estimates for Icelandic and Faroese waters are 3,142 and 287 whales respectively, although allowance was not made in the analysis for animals not observed because of their long dives (Reyes, 1991). Gunnlaugsson and Sigurjonsson (1990) estimate 5,827 whales at high latitudes in the Northeastern Atlantic and NAMMCO has calculated the population size of this species in the eastern part of the North Atlantic to be around 40,000 individuals (NAMMCO Annual Report 1995).
A study by Christensen and Ugland (1984) resulted in an estimated initial (pre-whaling) population size of about 90,000 whales, reduced to some 30,000 by 1914. The population size by the mid-1980's was said to be about 54,000, nearly 60% of the initial stock size.
Habitat
H. ampullatus is most common beyond the continental shelf and over submarine canyons, in deep water (>1,000m). It sometimes travels several kilometres into broken ice fields, but it is more common in open water. Few whales were caught over the continental shelf off Labrador and in waters less than 1,000m deep off the west coast of Norway. In the surrounding waters of Iceland, the whales were sighted at surface temperatures between -1.3°C and +0.9°C (Reyes, 1991).
Behaviour
The northern bottlenose whale is a curious animal: it will approach stationary boats and seems to be attracted by unfamiliar noises, such as those made by ships' generators. This, combined with its habit of staying with wounded companions, made it especially vulnerable to whalers. These deep divers can remain submerged for an hour, possibly as long as 2 h (Reeves et al. 1993, Bloch et al. 1996). Hooker and Baird (1999) showed that northern bottlenose whales in a submarine canyon off Nova Scotia exhibit an exceptional diving ability, with dives approximately every 80 min to over 800 m (maximum 1,453 m) depth, and up to 70 min in duration. Sonar traces of non-tagged, diving bottlenose whales in 1996 and 1997 suggest that such deep dives are not unusual. This shows that they may make greater use of deep portions of the water column than any other mammal so far studied. Many of the recorded dives of the tagged animals were to, or close to, the sea floor, consistent with benthic or bathypelagic foraging.
Reproduction
Northern bottlenose whales have a peak in calving in April (Jefferson et al. 1993).
Schooling
Most pods contain at least 4 whales, sometimes with as many as 20, and there is some segregation by age and sex (Mead, 1989, Jefferson et al. 1993). Northern bottlenose whales in the Gully also form small groups. Associations within age/sex classes (female /immature, subadult male and mature male) were significantly higher than associations between different classes. Females and immature bottlenose whales formed a loose network of associations, showing no preferential associations with particular individuals or those from specific age/sex classes nor any long-term bonds. Mature and subadult males had stronger associations with individuals in their own class, and associations between some males lasted for several years, although males also formed many short-term associations. Overall the social organization of northern bottlenose whales in the Gully appears to resemble that of some bottlenose dolphins, Tursiops truncatus, living in shallow, enclosed bays (Gowans et al. 2001).
Food
Although primarily adapted to feeding on squid, these whales also eat fish, sea cucumbers, starfish, and prawns. They apparently do much of their feeding on or near the bottom (Jefferson et al. 1993; Mead, 1989). Hooker et al. (2001) found a high proportion of the squid Gonatus steenstrupi in the stomachs of two bottlenose whales stranded in eastern Canada. They also collected remote biopsy samples from free-ranging bottlenose whales off Nova Scotia and determined fatty acid composition. Overall, the results of these techniques concurred in suggesting that squid of the genus Gonatus may form a major part of the diet of bottlenose whales in the Gully (Hooker et al. 2001).
Stomach content analysis by Clarke and Kristensen (1980) on a specimen stranded on the Faroe Islands showed that while the cephalopods found included six cold water species which were probably taken in deep water within the vicinity of the Faroes, they also included one species, Vampyroteuthis infernalis, which is a warmer water species and probably ranges little further north than 40°N. This suggests the whale had been much further south in the Atlantic than the Faroes at 62°N just before its stranding or that the distribution pattern of this cephalopod is not that well known. The stomach contents examined in the Faroese show more diversity with 13 species eaten than those from a whale stranded in Denmark (Clarke and Kristensen, 1980) and from whales shot off Labrador and Iceland, which contained only one species, Gonatus fabricii. Santos et al. (2001) report on stomach contents of bottlenose whales stranded in the North Sea. Their results are in agreement with those of previous authors in that cephalopods in general, and G. fabricii in particular, are the main prey of the northern bottlenose whale.
Migration
Migratory movements are poorly documented, as are stock relations among the animals found in apparently disjunct centres of spring and summer abundance (Reeves et al. 1993). In the eastern part of the range H. ampullatus probably moves north in spring and south in autumn; in the west, at least some animals are believed to overwinter at lower latitudes. There may also be some inshore-offshore movements (Carwardine, 1995).
In the western North Atlantic, bottlenose whales are present during much of the year in The Gully and in the Labrador Sea. Bottlenose whales in The Gully appear to be largely non-migratory, and this population of a few hundred whales might be vulnerable to the environmental degradation associated with nearby oil and gas production (Reeves et al. 1993). However, Gowans et al. (2000) found that over the summer field season, individuals emigrated from, and re-immigrated into the Gully, spending an average of 20 days within the Gully before leaving. Approximately 34% of the population was present in the Gully at any one time. Individuals of all age and sex classes displayed similar residency patterns although there were annual differences as individuals spent less time in the Gully in 1996 than in 1990 and 1997. Sighting rates were similar in all years with extensive fieldwork, indicating little variability in the number of whales in the Gully each summer.
Mitchell (1977) suggested that in the western North Atlantic, H. ampullatus may forage into the Northeast Channel and the Gulf of Maine in winter months.
A southward migration, better known in the eastern North Atlantic begins in July, when animals are moving south from the Norwegian Sea, and continues to September. The increase of strandings on the British coasts and on the North Sea coasts probably reflects part of this summer migration, which remains unknown in the northwest Atlantic. There is evidence from the distribution of catches that a northward migration occurs in the eastern North Atlantic in April-July (Reyes, 1991 and refs. therein). Bottlenose whales occur all year round in the Faroes, but with a distinct peak a fortnight around 1 September pointing at a very synchronized southernly migration route (Bloch et al. 1996).
This is further supported by MacLeod et al. (2004): Strandings of northern bottlenose whales on the coasts of the UK and the Republic of Ireland were lowest in April and highest in September. The number of strandings between months differed significantly from an even spread, with more strandings between July and October. Most strandings in late summer and autumn occurred on North Sea coasts and their stomach contents included the squid Gonatus fabricii, which is found only in more northern waters. This suggests that these whales may be migrating southward at this time of year.
Evidence of migratory movements of beaked whales in the Northeast Atlantic was obtained from an examination of historical strandings data from the United Kingdom and the Republic of Ireland, and from whaling records from the Faroes, Iceland and the Norwegian Sea. There is strong evidence to suggest that beaked whales, particularly northern bottlenose whales, undertake regular migrations, moving south-west in late summer and autumn and moving north-east in late winter and spring (MacLeod and Reid, 2003).
Threats
The main threats to the northern bottle-nosed whale are thought to be chemical and noise pollution, prey depletion, human disturbance, and hunting. This species has been hunted more than any of the other species of beaked whales. The extent to which populations of this species have been reduced by hunting is unclear, and the current status of the population is unknown.
From Carnivora.
carnivora.net/northern-bottlenose-whale-hyperoodon-ampullatus-t2777.html