Latest update: July 2021
The killer whale is the largest species in the family Delphinidae. The killer whale has a large body and a poorly defined beak compared to other dolphin species. A highly distinctive feature is its black and white colouring pattern. The body is largely black dorsally and white ventrally. Behind the eyes are noticeable oval-shaped white patches, referred to as eye patches. Behind the rear base of the dorsal fin is a grey patch, the so-called saddle patch. Pectoral fins (also called flippers) are oval in shape and the dorsal fin has a triangular shape, which may differ between individuals.
From the North Atlantic Sightings Survey (NASS) in 2001, it was estimated that there were around 15,000 killer whales in the North Atlantic between the Faroe Islands and Canada. From the 2014-2018, the Norwegian mosaic surveys (covering southern Norway, the northern North Sea and the Barents Sea) estimated around 14,00 killer whales in this area.
Killer whales are found worldwide and are widespread throughout the North Atlantic. They are, however, thought to be likely more abundant in the Northeast Atlantic than the Northwest Atlantic.
Killer whales are popular animals for whale watching activities and have also often been kept in captivity. They have been hunted opportunistically in Greenland.
NAMMCO provides advice to its member countries on the conservation status of killer whales, as well as on hunting activities in Greenland.
The species is listed as ‘Least Concern’ on the Icelandic (2018) and Norwegian (2015) national red lists and as ‘Data Deficient’ on the IUCN Red List for both the European and global stock in the most recent assessments (2007 and 2017, respectively).
Scientific name: Orcinus orca
Faroese: Bóghvítuhvalir / Mastrarhvalir
Norwegian: Spekkhogger, staurhval
English: Killer whale, Orca
Females live for an average of around 50 years, although the oldest known female in the wild was estimated to be 105 years old.
Males have an average lifespan of about 30 years (with maximum of around 60 years).
Females: 5-7 m, 3-4 metric tonnes (maximum recorded 8.5 m and 7.5 tonnes).
Males: 6-8 m, 5-6 metric tonnes (maximum recorded 10 m and 10 tonnes).
There is significant regional variation in the size of killer whales.
Migration and Movements
Killer whale movements seem to be mainly associated with the movement of their prey. This means that although some long distance movements have been documented, killer whales do not have a migration route in the North Atlantic as such.
As a species, they are considered a generalist predator with a diverse diet that includes bony fish, sharks, pinnipeds, other cetaceans, seabirds, reptiles and squid. However, some groups of killer whales can become specialists for certain prey, with adaptive behaviours for that prey.
At sea, the species can easily be identified due to its robust body, its tall standing dorsal fin, and unique black and white coloration. Even though the blow easily reaches 3 meters high, the black erect fin is the first discernible clue of their presence at sea. Killer whales are commonly found in groups.
The killer whale is the largest species in the family Delphinidae. The killer whale has a massive body and a poorly defined beak compared to other dolphin species. A highly distinctive feature of the killer whale is its black and white colouring pattern. The body is largely black dorsally and white ventrally. Behind the eyes are noticeable oval white patches, referred to as eye patches. Behind the rear base of the dorsal fin is a grey patch, the so-called saddle patch. Pectoral fins (also called flippers) are oval in shape and the dorsal fin has a triangular shape, which may differ between individuals.
Colouring pattern and morphology can greatly vary among regions and/or populations.
Sexual dimorphism is highly discernible in killer whales, both in terms of body length and the size of the dorsal fin. Flukes, pectoral and dorsal fins are much more developed in males than females. A male’s dorsal fin can easily be twice the height of a female’s.
When mature, male killer whales average 6-8 metres in length and 5-6 metric tonnes in weight, but they can reach up to 10 metres and weigh a maximum of 10 tonnes. Females average 5-7 metres in length and 3-5 metric tonnes in weight, and can reach a length of 8.5 meters and a weight of 7.5 tonnes.
Killer whale types
Although killer whales are currently considered a single species, evidence has suggested a more complex situation with the potential for separate species. Indeed, differences in colour pattern, diet, morphological traits, behaviour, acoustics and genetics have led to the description of a mosaic of types of killer whales throughout the world (Pitman & Ensor 2003, Morin et al. 2010, Foote et al. 2016). In the North Atlantic, the occurrence of two disparate types has been suggested. The generalist type 1 could be feeding on diverse prey types, with the diet of certain groups including both fish and mammals, whereas the specialist type 2 would be highly specialized on baleen whales (Foote et al. 2009).
Life history and ecology
Killer whales occur in groups, both in coastal and pelagic waters. They are one of the most popular marine mammals among whale watchers due to commonly displayed aerial behaviours including breaching (when a large part of the body is propulsed out of the water and lands on the sea surface in a huge splash), spy-hopping (when a whale rises its head vertically out of the water) and lob-tailing (when slapping the fluke on the sea surface). The meaning for these behaviours remains poorly understood but could have social implications.
Killer whales usually adopt a cruising speed of 10 to 13 km per hour, and they are able to maintain brief swimming speeds of 45 km per hour. Typically, killer whales remain less than a minute underwater but can extend their diving times to nearly 15 minutes. Killer whales tend to occur in the upper 20 m of the water column but can perform deep dives to 100-250 metres when foraging.
Killer whales are highly social animals that live in groups but social organisation and behaviour greatly vary with the environment they live in and the prey types that are hunted. The main stable unit for a group is a matriline, in which the oldest female (referred to as the matriarch) is the leader, accompanied by her daughters and sons and their offspring. A matriline can be particularly stable in composition and can gather up to 3-4 generations of related individuals. Dispersal from the natal group can occur but greatly depends, as does the group size, on the specific ecology and dietary habits of the group. Distinct but related matrilines can temporarily associate, leading to groups of several tens, or even a hundred individuals (Bigg et al. 1990).
Sound and Communication
Killer whales’ primary sense is their auditory system. They use three main types of sound, including echolocation clicks, whistles and calls. As a toothed whale species, killer whales produce low frequency, directional, broadband echolocation clicks and listen to their echo in order to get a ‘picture’ of their surroundings, as well as to navigate and locate their prey.
Loud calls are typically exchanged for long-range communication and movement coordination. These calls can be effective at ranges that exceed 10 to 20 km. Whistles appear to be used for close-range communication and behavioural interactions between individuals. The repertoire of calls, or dialect, is specific to each group (Ford 1991).
Female killer whales typically give birth to their first viable offspring at 12-14 years of age after a gestation period of 17-18 months. Calves are nursed for 1-2 years, gradually including solid foods into their milk diet. Females produce on average 4-5 calves throughout their reproductive lifespan. When they reach approximately 45 years of age, females become post-reproductive but may live for many years after this.
Males become sexually mature at about 15 years of age, after which their dorsal fin grows substantially.
Due to late sexual maturity, low calf production per female, and a prolonged post-reproductive phase, the potential for population growth and recovery is low among killer whales.
Diet and Feeding Behaviour
The killer whale, as a species, is considered a generalist predator with a diverse diet that includes bony fish, sharks, pinnipeds, other cetaceans, seabirds, reptiles and squid (Ford 2009). However, local populations may display strong prey preferences for which they develop specific feeding strategies and adaptive behaviours. A well known example of this is the two types of killer whales that occur in the coastal waters of BC, Canada and WA, USA. Whilst the resident type of killer whales are exclusively fish-eating, preferentially feeding on salmon species, the transient killer whales specialise on marine mammal prey (Baird & Dill 1995, Ford & Ellis 1998).
In the North Atlantic Ocean, killer whales also include a wide range of prey species. In Atlantic Canada, the prey taken by killer whales includes baleen whales (such as humpback whales and minke whales), toothed cetaceans (such as beluga whales and white-beaked dolphins), pinnipeds, seabirds, herring, and tuna (Sergeant & Fisher 1957, Whitehead & Glass 1985, Lawson et al. 2007). Whether groups of killer whales are generalist feeders or display group-specific prey specialisations is often unknown.
For the Canadian Arctic killer whale diet, only marine mammals have been reported as being part of their diet. This includes harp seals, ringed seals, bearded seals, harbour seals , hooded seals, narwhals, belugas and bowhead whales (Reeves & Mitchell 1988, Ferguson et al. 2012 ab, Higdon et al. 2012). This contrasts with killer whales from Greenland and Newfoundland-Labrador, where evidence suggests both fish and marine mammal prey.
Based on stomach contents, west Greenlandic killer whales appear to feed on fish prey (Heide-Jørgensen 1988), including lumpsucker fish (Cyclopterus lumpus) (Laidre et al. 2006) and Greenland halibut (Reinhardtius hippoglossoides), but also cephalopods (see Jensen & Christensen 2003) while killer whales off Tasiilaq (east Greenland) appear to feed mainly (and potentially exclusively) on marine mammals (Ugarte et al. 2013).
Killer whales off Iceland and Norway specialise and primarily feed on Atlantic herring (Clupea harengus), being mainly associated with the Icelandic Summer Spawning (ISS) and Norwegian Spring Spawning (NSS) stocks, respectively (Sigurjónsson et al. 1988, Similä et al. 1996, Simon et al. 2007, Foote et al. 2010, Samarra et al. 2012). Both sub-populations adopt similar feeding strategies in which the herring is cooperatively herded into a tight school below the sea surface, before they are debilitated with underwater tail-slaps and then consumed one by one (Simila & Ugarte 1993, Similä 1997, Simon et al. 2005). However, there have also been confirmed observations of killer whales preying on seabirds, grey seals, and minke whales in Icelandic waters (Vikingsson 2004) and a few individuals are known to seasonally return to Scotland for predation on seals (Foote et al. 2010, Samarra & Foote 2015).
Other prey items documented for Norwegian killer whales include cod, squid, bottlenose whales, mackerel, Atlantic salmon, pinnipeds and seabirds (Jonsgård 1968, Vester & Hammerschmidt 2013, Vongraen & Bisther 2014, Nøttestad et al. 2014). Around Scotland-UK, killer whales mainly prey on grey seals, harbour seals and mackerel (Weir 2002, Luque et al. 2006, Bolt et al. 2009, Deecke et al. 2011).
In several locations, killer whales have been observed associating with fishing vessels and scavenging around nets. This has been seen in the mackerel fisheries between Scotland and Norway and the herring fisheries off Northern Norway.
Much remains to be discovered about potential prey specialisations and local feeding behaviours in the North Atlantic. As more research provides increasing evidence of prey switching, an ecological gradient in ecotypes instead of classifications of generalist / specialist may emerge for the killer whales in the North East Atlantic (Bourque et al. 2018).
Distribution and Habitat
Killer whales are cosmopolitan. They are found in all the world’s oceans and are increasingly abundant in high latitude productive waters (Leatherwood & Dahlheim 1978, Forney & Wade 2006). Killer whales inhabit both coastal and offshore waters and their movement appears to be primarily associated with the availability and abundance of prey (Sigurjónsson & Leatherwood 1988, Similä et al. 1996).
Distribution in the North Atlantic
Killer whales have a wide range – from the east coast of Canada to Norwegian waters. They occur all along the eastern Canadian coast, from the Bay of Fundy and north to the Arctic (Sergeant & Fisher 1957, Whitehead & Glass 1985, Lien et al. 1988, Reeves & Mitchell 1988). They are most common in the Newfoundland and Labrador regions and are only seldom seen in the Gulf of St Lawrence, coastal Nova Scotia, the Bay of Fundy and north-eastern USA (Lawson et al. 2007). In the Eastern Canadian Arctic, killer whales occur seasonally during summer.
Canada, Greenland and Iceland
Historically, killer whales were known to occur in Canadian Arctic regions such as Davis Strait and Baffin Bay (Reeves & Mitchell 1988) but killer whale sightings have recently increased in Hudson Bay, presumably following a longer ice-free season that provides a greater open water habitat (Higdon 2007, Higdon & Ferguson 2009, Matthews et al. 2019).
Killer whales are known to occur all around Greenland, yet appear to be more common off western Greenland (Heide-Jørgensen 1988). A recent increase in killer whale sightings was observed off Tasiilaq, east Greenland (Ugarte et al. 2013, Lennert & Richard 2017).
Off Iceland, killer whales occur all along the coast all year round with a peak of observation in the summer herring grounds (Gunnlaugsson et al. 1988, Sigurjónsson et al. 1988).
British waters and the Norwegian coast
Killer whales are regularly sighted off the coast of the UK, the Northern Isles and the north-east of Scotland (Bolt et al. 2009, Foote et al. 2010, Beck et al. 2012). A subset of killer whales ranging off the east coast of Iceland is known to seasonally travel to Scotland (Foote et al. 2010, Samarra & Foote 2015). An assemblage of killer whales occurring off the west coast of Scotland, Ireland and Wales has been suggested to be a population isolated from neighbouring killer whales (Beck et al. 2014).
Killer whales occur all along the Norwegian coast, with the main concentrations off Northern Norway and Finnmark. The species also visits the waters around Svalbard and occurs throughout the Barents Sea (Kovacs et al. 2009, Storrie et al. 2018)
Even though long-distance movement – over 5000 km in a month (Matthews et al. 2011), and large ranges have been documented (Young et al. 2011), there is as yet no evidence for migration in the North Atlantic.
North Atlantic Stocks
Whilst effective conservation of marine predators requires the delineation of population units, or “stocks,” baseline information about abundance, distribution and movements between different locations is required for management purposes. In the North Atlantic, the preliminary investigations of killer whale abundance and distribution were largely based on whaling records, incidental observations, or stranding data. However recent efforts dedicated to describing populations have greatly improved our understanding of the species. Extensive studies conducted off Iceland, Norway and UK-Scotland, have resulted in over 1,000 individual killer whales identified across the north-east Atlantic and a comparison of identification catalogues has revealed site fidelity at several locations with distinct populations largely associated with particular prey resources (Foote et al. 2010).
Populations and management units
Due to high site and prey resources fidelity (shown by photo-identification studies e.g. Similä et al. 1996, Foote et al. 2010), the influence of diet, movement patterns, and contact between groups can be used as indicators of population structure and management units. In the Northeast Atlantic, three distinct killer whale populations have been suggested based on their association with their major prey source:
- The Atlantic herring population (including killer whales from the North Sea, Iceland and Norway),
- The Northeast Atlantic mackerel population, and
- The eastern stock of the Atlantic bluefin tuna (Thunnus thynnus) population (Foote et al. 2011).
Iceland and Norway
No movement between killer whale groups following the Icelandic Summer Spawning (ISS) and Norwegian Spring Spawning (NSS) herring stocks was detected by photo-identification data (Foote et al. 2010). However, genetics and acoustics has suggested former or on-going contact between the Icelandic and Norwegian sub-populations (Strager 1995, Simon et al. 2007, Foote et al. 2009, Samarra et al. 2010).
Killer whales ranging in British waters appear to belong to distinct populations. Large numbers of killer whales are known to occur off the east coast of the UK continuously distributed toward the Shetland and Faroe Islands, and are associated with the Northeast Atlantic mackerel stock during autumn (Luque et al. 2006, Foote et al. 2010). Off the Northern Isles and the northeast of Scotland, about 50 individuals are site-faithful, returning every spring-summer to feed on pinnipeds (Bolt et al. 2009, Foote et al. 2010, Beck et al. 2012). A subset of these killer whales belong to the herring feeding sub-population off the east coast of Iceland, from where they seasonally migrate (Foote et al. 2010, Beck et al. 2012, Samarra & Foote 2015). Another assemblage of killer whales occurring off the west coast of Scotland, Ireland and Wales was suggested as a population isolated from neighbouring killer whales (Beck et al. 2014).
In the northwest Atlantic, photographic data and simultaneous seasonal sightings in several regions such as Greenland and Newfoundland (Heide-Jørgensen 1988, Lien et al. 1988) suggest the possibility of several populations ranging in the western Atlantic.
The main management issue for this area lies in the fact that real baseline data on killer whale abundance, distribution and population structure in this region is missing (Higdon 2007). For effective management of the species, further data are needed. Biopsy sampling for genetic analyses could assist in assessing management units and possible movement between the Canadian Arctic/Atlantic and Greenland (Higdon 2007).
Total abundance in the North Atlantic
Killer whales are largely distributed throughout the North Atlantic but densities vary greatly among locations, presumably in relation to variation in resource distribution but also possibly due to former removals that may have negatively impacted population size.
Numerous abundance estimates have been produced at different scales for Northeastern Atlantic waters. Christensen (1988) estimated that about 483-1,507 killer whales could be using Norwegian coastal waters based on questionnaire-based surveys that reflected the period 1982-1987. Later on, line transect surveys conducted in the Norwegian Sea resulted in an estimate of 3,100 animals (Øien 1990). More recently, Kuningas and colleagues (2014) investigated demographics of killer whales associated with the NSS stock of herring and estimated this sub-population to be about 1,000 individuals. On a larger scale, a North Atlantic Sightings Survey (NASS 2001) produced an estimated number of 15,014 killer whales (95% CI: 6,637-33,964) between the Faroes and Atlantic Canada.
Following a literature review, killer whales were categorised as abundant in Norwegian waters, common off Iceland and the Faroe Islands, but rarely observed off the UK (Forney & Wade 2006). No abundance estimate currently exists for the Northwest Atlantic but based on available data, it has been suggested that the Northwest Atlantic population is not as large as the one in the Northeastern Atlantic (Lawson & Stevens 2014).
Abundance in different areas
Atlantic and Arctic Canada
Due to a relatively large study area, little observer coverage and only a recent establishment of systematic effort in monitoring killer whale occurrence, there is currently no reliable estimate of killer whale abundance for Atlantic Canada. However, recent efforts have enabled photo-identification of a minimum of 67 individuals in the Newfoundland and Labrador regions (Lawson et al. 2013). In Canadian Arctic waters, a minimum of 53 individuals have been identified, with no re-sighting detected between Arctic and Newfoundland-Labrador killer whales (Young et al. 2011). Little is known about killer whales ranging in these two distinct regions and these numbers are undoubtedly under-estimates of killer whale abundance.
Killer whales do not appear to be abundant in Greenlandic waters, as suggested by the very few sightings during yearly fishery surveys (Ugarte et al. 2013). No killer whale abundance estimate currently exists for this region and preliminary results of photo-identification attempts resulted in only 15 individuals identified (source catalogue available at www.descna.com).
Preliminary abundance estimates range from 4,000 to 6,847 killer whales, but these numbers may include killer whales from several populations over large areas (Gunnlaugsson & Sigurjónsson 1990). A recent study identified a minimum of 314 individuals regularly using the waters off the southern and west coasts of Iceland (Tavares et al. 2016).
Killer whales are encountered year-round in UK waters but no abundance estimate exists for this specific location (Reid et al. 2003). Based on evidence that some killer whales may be widely travelling in this part of the Northeast Atlantic, it is likely that available abundance estimates include killer whales from UK waters as well (Samarra & Foote 2015).
Various abundance estimates have been generated for killer whales off the Norwegian coast over time. In the 1980s, Christensen (1988) estimated that at least 1,500 killer whales could be using Norwegian coastal waters when the herring over-wintered close to shore. A later North Atlantic Sighting Survey (NASS) provided an estimate of 7,000 killer whales ranging in Norwegian waters (Øien 1993), although these whales likely belonged to several populations.
Long-term photo-identification studies have enabled a cataloging of 686 individual killer whales occurring in the winter herring ground in 1986-2005 and 2007-2013 and a total abundance estimate of about 1,000 individuals was suggested on the basis of this work (Similä et al. 1996, Kuningas et al. 2014). As the identification study continues, a minimum (and temporary) number of 862 individual killer whales appear to be regularly using the coastal waters of Northern Norway (Jourdain & Karoliussen 2016).
The Norwegian mosaic surveys (covering southern Norway, the northern North Sea and the Barents Sea) have also generated a series of abundance estimates for killer whales (NAMMCO 2019). For the 2002-2007 cycle, abundance was estimated at 18,213 animals (95% CI: 11,486 – 29,992). In the 2008-2013 period, the abundance estimated was 8,984 animals (95% CI: 4,494 – 17,963). For 2014-2018, abundance was estimated as 13,909 animals (95% CI: 7,733 – 25,018).
Changes in trends
Western North Atlantic
While killer whales were historically present in Davis Strait and Baffin Bay in Arctic Canada, they recently extended their range to Hudson Bay, a region that has become regularly visited. The bay typically undergoes a yearly cycle with sea-ice formation from late October and breakup during the summer months. Sea ice persisting throughout the year in Hudson Strait may have prevented killer whales from using the bay, despite a great diversity of marine mammal prey available.
A marked climate shift has resulted in a drastic decrease in both extent and duration of sea ice in Hudson Bay. Since the 1950s, killer whale sightings have dramatically increased here. Visits have been possibly yearly from the 1980s, presumably in relation to a longer ice-free season that provides a suitable open water habitat (Gagnon & Gough 2005, Higdon 2007, Higdon & Ferguson 2009). As killer whales are known to largely prey on cetaceans in this region, predation on belugas, narwhals and bowhead whales may increase significantly with potential negative impacts on these prey populations (Ferguson et al. 2010). Concerns for the recovery of the Eastern Canada-Western Greenland bowhead whales have been raised (Reinhart et al. 2013).
Eastern North Atlantic
During the last decade, killer whales have also become more common off Tasiilaq, East Greenland. However, it is unknown if this shift in distribution and/or abundance is related to a shift of prey, increasing water temperatures, decreasing ice cover or a combination of these factors (Ugarte et al. 2013).
Off Norway, shifts in the herring wintering distribution since 2007 have resulted in a possible increase in killer whale abundance during these months. Indeed, the wintering ground for the NSS stock of herring, formerly located in inner fjords of the Lofoten region, shifted to more open waters mainly located between 69°N and 73°N (Huse et al. 2010) over the last decade. The displacement of the wintering herring ground to a more open area may have brought this abundant prey resource within the reach of additional killer whale groups, as suggested by new adult individuals identified since 2011 that were not present in the former catalogues. However, such increase in killer whale abundance on the herring wintering ground is likely to reflect shifts in killer whale distribution from other locations in response to a dynamic prey resource rather than an increase in abundance of killer whales per se.
The Northwest Atlantic population of killer whales is managed as one unit and is listed as a species of Special Concern under COSEWIC (COSEWIC 2008). Hunting activity in Greenland was listed as a threat to this population.
Killer whales in the Northeastern Atlantic appear to be associated to specific prey resources and three distinct populations have been suggested (Foote et al. 2009) – see section on North Atlantic Stocks. However, due to a small sample size relative to high abundance estimates, and poorly understood movement patterns across the Atlantic, delineation of management units remains to be improved, with further baseline information required at local levels. For instance, a small community of 10 killer whales found off Western Scotland, Ireland and Wales appears to be isolated from other local killer whale groups, with which no association has been observed. Because no new individuals have been born in nearly 20 years of monitoring, this isolated group is in decline and was recommended to be managed as a separate conservation unit (Beck et al. 2014).
NAMMCO provides management advice to the Faroe Islands, Greenland, Iceland and Norway and on the conservation status of killer whales. Killer whales in Eastern Canada are managed by the Department of Fisheries and Oceans, and the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has reviewed the species, listing the killer whales in Eastern Canada as “threatened.”
From 1938-1981, killer whales were caught over a wide area of the North Atlantic and reported catches included 1,961 animals in Norwegian coastal and offshore waters, Barents Sea, Jan Mayen, Bear Island and Svalbard, 140 in the North Sea, 153 in Iceland and 181 off Eastern and Southern Greenland. Although the target species of whaling operations was the minke whale, other cetaceans such as killer whales were caught when encountered. Killer whale catches were of minor commercial value to the whalers and the meat was only used as food for pets and fur farms. From the late 1960s, killer whales were also caught in response to complaints from fishermen that killer whales were interfering with the recovery of the depleted herring stock (Øien 1988).
Killer whales have always been hunted in Greenland, mainly opportunistically. A bounty was introduced in 1960 and maintained until 1975. Only 10 catches were reported, but this is likely an underestimate, not accounting for whales struck and lost (Heide-Jørgensen 1988). As of today, killer whales are legally hunted off Greenland, and reporting catches has been obligatory since 1996. A minimum of 130 killer whales has been taken since the 1950s (with a gap in data available for the period 1987-1995). Since 2008, a sharp increase in killer whale catches was recorded off Tasiilaq, East Greenland, where what was previously opportunistic and rare game has become a more regular hunt. No regulations for killer whale hunting currently exist in Greenland, and conservation related questions have been raised (Ugarte et al. 2013, Jourdain et al. 2019), particularly as killer whales eating marine mammals around Greenland have been documented to have extremely high PCB levels (Pedro et al. 2017), which adds further pressure on the species.
Killer whale hunting in Norway dates back to 1920, however catches were recorded only from 1938 (Bloch & Allison 2005). After licensing of small-type whaling was introduced in Norway in 1938, all killer whale catches had to be reported and the logbooks indicated 2,435 killer whales were caught from 1938 to 1981 (Øien 1988). In 1982, killer whales became protected by Norwegian law.
In Canada, killer whales were hunted either as a target or competitor species until 1972, when commercial whaling was banned (Lawson et al. 2007). Currently, only whaling for subsistence purposes by indigenous communities remains permitted, based on the importance of whales as a source of food and cultural traditions for these communities (Higdon 2007). However, lethal interactions with fisheries may still occur, as suggested by a photograph recently taken of a killer whale calf displaying a bullet wound on its head (Lawson et al. 2007).
REPORTED CATCHES IN NAMMCO MEMBER COUNTRIES
|Country||Year or Season||Area||Catch Total|
|Greenland||1992-1995||Total||*No reported catches|
This database of reported catches is searchable, meaning you can filter the information by for instance country, species or area. It is also possible to sort it by the different columns, in ascending or descending order, by clicking the column you want to sort by and the associated arrows for the order. By default, 30 entries are shown, but this can be changed in the drop-down menu, where you can decide to show up to 100 entries per page.
Carry-over from previous years are included in the quota numbers, where applicable.
You can find the full catch database with all species here.
For any questions regarding the catch database, please contact the Secretariat at firstname.lastname@example.org.
59 (1976-1988; Sigurjónsson & Leatherwood, 1988) and 64 (1960-1983; Bloch & Lockyer, 1988) killer whales were live-captured the 1960s to 1980s in Icelandic and Faroese waters, respectively. The purpose of these captures was sale and export to oceanariums.
Other Human Impacts
The main threats to killer whales include pollution, prey depletion and to a lesser extent ship-strikes, oil spills, boat traffic (and associated acoustic disturbance) and lethal interactions with fisheries (e.g. Poncelet et al. 2010).
Anthropogenic contaminants such as pesticides, industrial organics, and heavy metals have become widely distributed throughout natural habitats. Being highly toxic and persistent, they accumulate up food webs, contaminating organisms and causing deleterious effects. Because killer whales are long-lived apex predators, they accumulate high concentrations of these contaminants (Ross et al. 2000, Wolkers et al. 2007, Jepson et al. 2016, Pedro et al. 2017). Some documented negative effects of contaminants include reproductive and immune system impairment, disruption of the hormone system and increased prevalence of cancer. Whilst elevated contaminant loads have been measured in declining cetacean populations in Europe, contaminant exposure could have significant effects at the population level through lower recruitment induced by reproductive toxicity (Jepson et al. 2016).
In a study by Desforges et al. (2018) PCB levels in different killer whale populations were compared and it was concluded that 10 out of 19 populations have either a moderate or high risk of extinction in the future due to PCB pollution. These threatened killer whale stocks would either be living in some of the most polluted areas or they would be feeding on marine mammals. This would mean that killer whales around Norway and Iceland that primarily feed on fish may be fine, but those coming to southeast Greenland feeding on marine mammals would be at a high risk of decline. The model used in this work was later critiqued (Witting 2019) and although this critique did not contradict chemical contamination as a challenge for killer whale populations, it did question the validity of the predicted collapse of populations. The authors responded to this critique and emphasised that they felt the weight of evidence indicates that the current level of exposure in many killer whale populations can have potentially severe implications and that this risk should not be ignored (Desforges et al. 2019).
Due to overfishing and degradation of habitats, killer whales may have to deal with low prey concentrations at particular locations. Availability of prey species has been shown to have effects on both survival and reproduction of killer whales (Ward et al. 2009, Ford et al. 2010). Such information is of particular concern for killer whale groups or populations showing high levels of prey specialisation due to high dependence on certain prey resources. Consequently, by impacting recruitment and survival, prey availability can influence population growth.
Contact with oil spills may have lethal effects on killer whales through inhalation of toxic vapours or ingestion of oil. Such major environmental perturbation has the potential to lead entire groups and/or populations into a sharp decline or even extinction (Matkin et al. 2008).
By-catch and entanglements
Although not very common, incidental mortality caused by fishing gear has been reported (Lawson et al. 2007). Indeed, killer whales may deliberately associate with fishing boats, as has been documented between Scotland and Norway with the mackerel and herring fisheries (Luque et al. 2006), and this can increase the potential for by-catch and entanglement. Scavenging around fishing nets may provide killer whales with an important proportion of their daily energy requirements and appears to have become an emerging feeding strategy in several locations. Off Northern Norway, killer whales commonly associate with the commercial herring trawlers during the winter months and several cases of killer whales trapped in purse seine nets have been recorded.
Disturbance from anthropogenic noise sources create various behavioural responses, of differing severity, in North Atlantic killer whales. Particularly during foraging activities, where acoustic disturbance causes disruption in feeding dives, separation and displacement of group members as a result of noise avoidance (Kuningas et al. 2013, Samarra & Miller 2016). Furthermore, vessel traffic influences the activity budget of killer whales, leaving less time for foraging and could reduce foraging success (Lussea et al. 2009). The effects of noise disturbance in North Atlantic killer whales have, however, not been comprehensively assessed to date.
The Greenland Institute of Natural Resources (GINR) occasionally conducts interview surveys among hunters and collects biological samples from killer whale catches. Even though data are opportunistically collected, preliminary results indicate that killer whale hunting that was historically a rare activity, has become more important in the region of Tasiilaq.
A few samples collected from Greenlandic killer whales were included in a global study that aimed at identifying killer whale populations across the North Atlantic (Foote et al. 2013). These killer whales appear to be related to the herring and mackerel feeding killer whales found in Iceland, Norway and in the North Sea. Studies to evaluate contamination levels of the killer whales caught off Tasiilaq and potential effects for humans that consume the meat are underway at Aarhus University, Denmark.
The Marine and Freshwater Research Institute (MFRI) initiated the first investigations of killer whales occurring in the herring overwintering grounds of East Iceland. Currently, the Institute, along with the Icelandic Orca Project and the Sea Mammal Research Unit (Saint Andrews, Scotland), are the main actors monitoring population abundance and structure, acoustics, behaviour, feeding ecology and levels of contamination. The Icelandic killer whale catalogue containing over 400 killer whale individuals identified between 2006 and 2015 was published on the MFRI website in 2017.
A long-term project on killer whales was started in 2008, with a current focus on investigating dietary specialisation and acoustic behaviour, and observing interspecific interactions with pilot whales (National Progress Report Iceland 2020). The MRFI, University of Iceland (UI) and the Icelandic Orca Project conduct fieldwork in Vestmanaeyjar during summers, collecting information on prey targeted and dietary preferences of individual whales through the scollection of photo-identifications and observations of feeding events. Two moored hydrophones were also deployed in 2018 to monitor cetacean occurrence in the area and the effects of vessel noise (National Progress Report Iceland 2018).
During line-transect surveys dedicated to monitor cetacean abundance across the Norwegian Sea during the summer months, the Institute of Marine Research (IMR, Bergen, Norway) has recorded killer whale occurrence and produced data about killer whale distribution and abundance in these waters (e.g. Nøttestad et al. 2015).
The Norwegian Orca Survey
The Norwegian Orca Survey (Andenes, Norway) is a non-profit research organisation established in 2013 that is dedicated to long-term monitoring of killer whales occurring off Northern Norway. The main goals of the organisation include studying population abundance, foraging ecology and habitat use. The ongoing research also aims to continue the photo-identification study initiated by colleagues in 1986 (Similä et al. 1996, Vongraven & Bisther 2013). As part of this project, efforts have been directed towards further data collection throughout the year in Northern Norway. This includes collection of ID-photographs, biopsy samples, behavioural observations, aerial (drone) imagery, sound recordings and prey remains. Data are being used for various studies based on individuals’ recognition, including mark-recapture analyses and investigations of group-specific foraging ecology. The Norwegian killer whale identification database is a work in constant progress and the latest version of the ID-catalogue was published in March 2018 (Jourdain & Karoliussen 2018). The Norwegian Orca ID-project also relies on citizens’ photographs which contribute by building individual killer whales’ sighting histories and this ID-Catalogue.
Through this ongoing research on killer whales, molecular identification of prey species foraged upon in spring documented a new prey species: the lumpfish (Cyclopterus lumpus) (National Progress Report Norway 2019). 75 photo-identified killer whales that returned to Andfjord in spring for temporary residency were found to forage upon lumpfish as the fish migrates to coastal habitats for spawning. These whales are also known to be herring-eaters from winter observations in the same years. This research (Jourdain et al. 2019b) was the first documentation of individual killer whales seasonally switching between alternative resources. Analysis of dietary markers confirmed that the Norwegian killer whale population is generalist, with dietary habits varying between groups (Jourdain et al., 2020). There appears to be an ecological gradient between fish specialists and others that, to some extend, specialize on pinnipeds. The pinniped-eating killer whales that were sampled were also found to include fish in their diets, and are therefore not prey-specialists (Jourdain et al., 2020).
The Whaletrack project
The Arctic University of Norway (UiT, Tromsø, Norway) conducted tagging experiments on killer whales during the winter months in 2015-2017. The Whaletrack project was initiated in 2013 with an aim to map humpback and killer whale behaviour and migration related to their winter aggregations in the Northern Norwegian fjords. In 2018, the Whalefeast project was also included under the Whaletrack framework. The UiT Arctic University of Norway leads the project, with close cooperation with the Institute for Marine Research (IMR, Tromsø and Bergen). The project also includes cooperation with other Norwegian and international institutions and has several PhD and MSc candidates associated with it.
The main purpose of the project is to gain better knowledge about the behavior of humpback and killer whales before, during and after the period they feed on overwintering herring in the fjords or off the coast of Northern Norway. Whilst the Whaletrack project has focused on mapping the horizontal and vertical migration patterns of humpback and killer whales, the Whalefeast project (2018-2021) also includes a closer cooperation with the fisheries and tourism industry, as well as using eDNA-techniques in addition to already collected data. It includes social science studies of the impacts that the whale arrivals have and have had on the tourist and fisheries industries (National Progress Report Norway 2018).
Ocean Sounds is a non-profit organisation focusing on the biology, acoustics and education about whales and dolphins in several locations worldwide, including killer whales occurring in the Lofoten region in Norway.
Baird, R.W. and Dill, L. M. (1995). Occurrence and behaviour of transient killer whales: seasonal and pod-specific variability, foraging behaviour, and prey handling. Canadian Journal of Zoology, 73(7), 1300-1311. https://doi.org/10.1139/z95-154
Beck, S., Foote, A.D., Kötter, S., Harries, O., Mandleberg, L., Stevick, P.T., … and Durban, J. W. (2014). Using opportunistic photo-identifications to detect a population decline of killer whales (Orcinus orca) in British and Irish waters. Journal of the Marine Biological Association of the United Kingdom, 94(6), 1327. https://doi.org/10.1017/S0025315413001124
Beck, S., Kuningas, S., Esteban, R. and Foote, A.D. (2012). The influence of ecology on sociality in the killer whale (Orcinus orca). Behavioral Ecology, 23(2), 246-253. https://doi.org/10.1093/beheco/arr151
Bigg, M. A., Olesiuk, P. F., Ellis, G. M., Ford, J. K. B. and Balcomb, K. C. (1990). Social organization and genealogy of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Reports of the International Whaling Commission, 12, 383-405.
Bloch, D. and Allison, C. (2005). Whale catches in the North Atlantic 1894-1984, taken by Norway, the Faroes, Shetland, the Hebrides, Ireland and Greenland. NAMMCO SC/13/18: 1- 46.
Bloch, D. and Lockyer, C. (1988). Killer whales (Orcinus orca) in Faroese waters. Rit Fiskideildar 11, 55-64.
Bolt, H. E., Harvey, P. V., Mandleberg, L. and Foote, A. (2009). Occurrence of killer whales in Scottish inshore waters: temporal and spatial patterns relative to the distribution of declining harbour seal populations. Aquatic Conservation: Marine and Freshwater Ecosystems, 19(6), 671-675. https://doi.org/10.1002/aqc.1030
Bourque, J., Dietz, R., Sonne, C., St Leger, J., Iverson, S., Rosing-Asvid, A., Hansen, M. and McKinney, M. A. (2018). Feeding habits of a new Arctic predator: insight from full-depth blubber fatty acid signatures of Greenland, Faroe Islands, Denmark, and managed-care killer whales Orcinus orca. Marine Ecology Progress Series 603, 1–12. https://doi.org/10.3354/meps12723.
Christensen, I. (1988). Distribution, movements and abundance of killer whales (Orcinus orca) in Norwegian coastal waters, 1982-1987, based on questionnaire surveys.
COSEWIC. (2008). COSEWIC assessment and update status report on the Killer Whale Orcinus orca, Southern Resident population, Northern Resident population, West Coast Transient population, Offshore population and Northwest Atlantic/Eastern Arctic pop- ulation, in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa, Canada. viii + 65 pp.
Deecke, V. B., Nykänen, M., Foote, A. D. and Janik, V. M. (2011). Vocal behaviour and feeding ecology of killer whales Orcinus orca around Shetland, UK. Aquatic Biology, 13(1), 79-88. https://doi.org/10.3354/ab00353
Desforges, JP., Hall, A., McConnell, B., Asvid, A. R., Barber, J. L., Brownlow, A., … and Dietz, R. (2019). Response to L. Witting: PCBs still a major risk for global killer whale population. Marine Mammal Science, 35, 1201-1206. https://doi.org/10.1111/mms.12615
Desforges, JP., Hall, A., McConnell, B., Asvid, A. R., Barber, J. L., Brownlow, A., … and Dietz, R. (2018). Predicting global killer whale population collapse from PCB pollution. Science 361, 1373-1376. https://doi.org/10.1126/science.aat1953
Ferguson, S. H., Higdon, J. W. and Westdal, K. H. (2012a). Prey items and predation behavior of killer whales (Orcinus orca) in Nunavut, Canada based on Inuit hunter interviews. Aquatic Biosystems, 8(1), 1. https://doi.org/10.1186/2046-9063-8-3
Ferguson, S. H., Kingsley, M. C. and Higdon, J. W. (2012b). Killer whale (Orcinus orca) predation in a multi-prey system. Population Ecology, 54(1), 31-41. https://doi.org/10.1007/s10144-011-0284-3
Ferguson, S. H., Higdon, J. W. and Chmelnitsky, E. G. (2010). The rise of killer whales as a major Arctic predator. In Ferguson, S. H., Loseto, L. L. and Mallory, M. L. (eds.), A Little Less Arctic (pp. 117-136). Dordrecht: Springer. https://doi.org/10.1007/978-90-481-9121-5_6
Foote, A. D., Vijay, N., Ávila-Arcos, M. C., Baird, R. W., Durban, J. W., Fumagalli, M., … and Robertson, K. M. (2016). Genome-culture coevolution promotes rapid divergence of killer whale ecotypes. Nature communications, 7. https://doi.org/10.1038/ncomms11693
Foote, A. D., Newton, J., Ávila-Arcos, M. C., Kampmann, M. L., Samaniego, J. A., Post, K., … and Gilbert, M. T. P. (2013). Tracking niche variation over millennial timescales in sympatric killer whale lineages. Proceedings of the Royal Society of London B: Biological Sciences, 280(1768), 20131481. https://doi.org/10.1098/rspb.2013.1481
Foote, A. D., Vilstrup, J. T., De Stephanis, R., Verborgh, P., Abel Nielsen, S. C., Deaville, R., … and Pérez-Gil, M. (2011). Genetic differentiation among North Atlantic killer whale populations. Molecular Ecology, 20(3), 629-641. https://doi.org/10.1111/j.1365-294X.2010.04957.x
Foote, A.D., Similä, T., Víkingsson, G.A. and Stevick, P.T. (2010) Movement, site fidelity and connectivity in a top marine predator, the killer whale. Evolutionary Ecology, 24, 803–814. https://doi.org/10.1007/s10682-009-9337-x
Foote, A. D., Newton, J., Piertney, S. B., Willerslev, E. and Gilbert, M. T. P. (2009). Ecological, morphological and genetic divergence of sympatric North Atlantic killer whale populations. Molecular Ecology, 18(24), 5207-5217. https://doi.org/10.1111/j.1365-294X.2009.04407.x
Ford J.K.B., Ellis G.M., Olesiuk P.F. and Balcomb K.C. (2010) Linking killer whale survival and prey abundance: food limitation in the ocean’s apex predator? Biology Letters, 6, 139–142. https://doi.org/10.1098/rsbl.2009.0468
Ford, J. K. B. (2009). Killer whales Orcinus orca. In W. F. Perrin, B. Würsig, and J. G. M. Thewissen (eds.), The encyclopedia of marine mammals (2nd ed., pp. 650-657). San Diego: Academic Press. https://doi.org/10.1016/B978-0-12-373553-9.00150-4
Ford, J. K. B., Ellis, G. M., Barrett-Lennard, L. G., Morton, A. B., Palm, R. S. and Balcomb III, K. C. (1998). Dietary specialization in two sympatric populations of killer whales (Orcinus orca) in coastal British Columbia and adjacent waters. Canadian Journal of Zoology, 76(8), 1456-1471. https://doi.org/10.1139/z98-089
Ford, J. K. B. (1991). Vocal traditions among resident killer whales (Orcinus orca) in coastal waters of British Columbia. Canadian Journal of Zoology, 69, 1454–1483. https://doi.org/10.1139/z91-206
Forney, K. A. and Wade, P. R. (2006). Worldwide distribution and abundance of killer whales. In Estes, J. (ed.), Whales, whaling and ocean ecosystems (pp. 145-162). https://doi.org/10.1525/california/9780520248847.003.0012
Gagnon, A. S., and W. A. Gough. 2005. Trends in the dates of ice freeze-up and breakup over Hudson Bay, Canada. Arctic 58:370–382. https://doi.org/10.14430/arctic451
Gunnlaugsson, T. and Sigurjónsson, J. (1990). NASS-87: Estimation of whale abundance based on observations made onboard Icelandic and Faroese survey vessels. Reports of the International Whaling Commission, 40, 571-580.
Gunnlaugsson, T., Sigurjónsson, J. and Donovan, G. P. (1988). Aerial survey of cetaceans in the coastal waters of Iceland, June-July 1986. Reports of the International Whaling Commission, 38.
Heide-Jørgensen, M. P. (1988). Occurrence and hunting of killer whales in Greenland. Rit Fiskideildar 11, 115-135.
Higdon, J. W., Hauser, D. D. and Ferguson, S. H. (2012). Killer whales (Orcinus orca) in the Canadian Arctic: Distribution, prey items, group sizes, and seasonality. Marine Mammal Science, 28(2), E93-E109. https://doi.org/10.1111/j.1748-7692.2011.00489.x
Higdon, J. W., and Ferguson, S. H. (2009). Loss of Arctic sea ice causing punctuated change in sightings of killer whales (Orcinus orca) over the past century. Ecological Applications, 19(5), 1365-1375. https://doi.org/10.1890/07-1941.1
Higdon, J. (2007). Status of knowledge on killer whales (Orcinus orca) in the Canadian Arctic. Canadian Science Advisory Secretariat. https://www.academia.edu/2489358/Status_of_knowledge_on_killer_whales_Orcinus_orca_in_the_Canadian_Arctic
Huse, G., Fernö, A. and Holst, J. C. (2010). Establishment of new wintering areas in herring co-occurs with peaks in the ‘first time/repeat spawner’ratio. Marine Ecology Progress Series, 409, 189-198. https://doi.org/10.3354/meps08620
Jensen, D. B. and K. D. Christensen (eds.). (2003). The biodiversity of Greenland – a county study. Technical Report No. 55. Pinngortitalerifik: Grønlands Naturinstitut.
Jepson, P.D., Deaville, R., Barber, J.L. et al. (2016). PCB pollution continues to impact populations of orcas and other dolphins in European waters. Nature – Scientific Reports 6, 18573. https://doi.org/10.1038/srep18573
Jonsgård, A. (1968). A note on the attacking behaviour of the killer whale (Orcinus orca). Norsk Hvalfangst-Tidende, 57, 84-85.
Jourdain, E, Andvik, C, Karoliussen, R, Ruus, A, Vongraven, D, Borgå, K. (2020). Isotopic niche differs between seal and fish‐eating killer whales (Orcinus orca) in northern Norway. Ecology and Evolution 2020; 00: 1-13. doi: 10.1002/ece3.6182.
Jourdain, E., Ugarte, F., Víkingsson, G.A., Samarra, F.I.P., Ferguson, S.H., Lawson, J., Vongraven, D. and Desportes, G. (2019a). North Atlantic killer whale Orcinus orca populations: a review of current knowledge and threats to conservation. Mammal Review, 49, 384-400. https://doi.org/10.1111/mam.12168
Jourdain, E., Karoliussen, R., de Vos, J., Zakharov, S.E. and Tougard, C. (2019b). Killer whales (Orcinus orca) feeding on lumpfish (Cyclopterus lumpus) in northern Norway. Marine Mammal Science, 36, 1-14. https://doi.org/10.1111/mms.12618.
Jourdain, E. and Karoliussen, R. (2018). Identification Catalogue of Norwegian killer whales : 2007-2018. doi: 10.6084/m9.figshare.4205226.
Jourdain, E. and Karoliussen, R. (2016). The Norwegian Orca ID-Catalogue. doi: 10.6084/m9.figshare.4205226.
Kovacs, K. M., Haug, T. and Lydersen, C. (2009) Marine mammals of the Barents Sea. In Sakshaug, E., Johnsen, G. and Kovacs, K. M. (eds.), Ecosystem Barents Sea (pp. 453–497). Trondheim: Tapir Academic Press.
Kuningas, S., Similä, T. and Hammond, P. S. (2014). Population size, survival and reproductive rates of northern Norwegian killer whales (Orcinus orca) in 1986–2003. Journal of the Marine Biological Association of the United Kingdom, 94(06), 1277-1291. https://doi.org/10.1017/S0025315413000933
Laidre, K. L., Heide-Jørgensen, M. P. and Orr, J. R. (2006). Reactions of narwhals, Monodon monoceros, to killer whale, Orcinus orca, attacks in the eastern Canadian Arctic. The Canadian Field-Naturalist, 120(4), 457-465. https://doi.org/10.22621/cfn.v120i4.355
Lawson, J. W. and Stevens, T. S. (2014). Historic and current distribution patterns, and minimum abundance of killer whales (Orcinus orca) in the north-west Atlantic. Journal of the Marine Biological Association of the United Kingdom, 94(06), 1253-1265. https://doi.org/10.1017/S0025315413001409
Lawson, J. W., Stevens, T. S. and Snow, D. (2007). Killer whales of Atlantic Canada, with particular reference to the Newfoundland and Labrador Region, Research Document 2007/062. Ottawa: Fisheries and Oceans Canada, Canadian Science Advisory Secretariat.
Leatherwood, J. S. and Dahlheim, M. E. (1978). Worldwide distribution of pilot whales and killer whales. Naval Ocean Systems Center. Tech. Rep., 443, 1-39.
Lennert, A. E. and Richard, G. (2017). At the cutting edge of the future: unravelling depredation, behaviour and movement of killer whales in the act of flexible management regimes in Arctic Greenland. Ocean and Coastal Management, 148, 272–281. https ://doi.org/10.1016/j.oceco aman.2017.08.016.
Lien, J., Stenson, G. B. and Jones, P. W. (1988). Killer whales (Orcinus orca) in waters off Newfoundland and Labrador, 1978-1986.
Luque, P. L., Davis, C. G., Reid, D. G., Wang, J. and Pierce, G. J. (2006). Opportunistic sightings of killer whales from Scottish pelagic trawlers fishing for mackerel and herring off North Scotland (UK) between 2000 and 2006. Aquatic Living Resources, 19(4), 403-410. https://doi.org/10.1051/alr:2007009
Lusseau, D., Bain, D. E., Williams, R. and Smith, J. C. (2009). Vessel traffic disrupts the foraging behavior of southern resident killer whales Orcinus orca. Endangered Species Research, 6, 211–221. https://doi.org/10.3354/esr006211.
Matkin, C. O., Saulitis, E. L., Ellis, G. M., Olesiuk, P. and Rice, S. D. (2008). Ongoing population-level impacts on killer whales Orcinus orca following the ‘Exxon Valdez’oil spill in Prince William Sound, Alaska. Marine Ecology Progress Series, 356, 269-281. https://doi.org/10.3354/meps07273
Matthews, C. J. D., Raverty, S. A., Noren, D. P., Arragutainaq, L. and Ferguson, S. H. (2019) Ice entrapment mortality may slow expanding presence of Arctic killer whales. Polar Biology, 42, 639-644. https ://doi.org/10.1007/s00300-018-02447-3.
Matthews, C. J., Luque, S. P., Petersen, S. D., Andrews, R. D. and Ferguson, S. H. (2011). Satellite tracking of a killer whale (Orcinus orca) in the eastern Canadian Arctic documents ice avoidance and rapid, long-distance movement into the North Atlantic. Polar Biology, 34(7), 1091-1096. https://doi.org/10.1007/s00300-010-0958-x
Morin, P. A., Archer, F. I., Foote, A. D., Vilstrup, J., Allen, E. E., Wade, P., … and Bouffard, P. (2010). Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome research, 20(7), 908-916. https://doi.org/10.1101/gr.102954.109
North Atlantic Marine Mammal Commission (NAMMCO). (2019). Report of the Abundance Estimates Working Group. October 2019. Tromsø, Norway. https://nammco.no/topics/abundance_estimates_reports/
Nøttestad, L., Krafft, B. A., Anthonypillai, V., Bernasconi, M., Langård, L., Mørk, H. L. and Fernö, A. (2015). Recent changes in distribution and relative abundance of cetaceans in the Norwegian Sea and their relationship with potential prey. https://doi.org/10.3389/fevo.2014.00083
Nøttestad, L., Sivle, L. D., Krafft, B. A., Langård, L., Anthonypillai, V., Bernasconi, M., … and Fernö, A. (2014). Prey selection of offshore killer whales Orcinus orca in the Northeast Atlantic in late summer: spatial associations with mackerel. Marine Ecology Progress Series, 499, 275-283. https://doi.org/10.3354/meps10638
Pedro, S., Boba, C., Dietz, R., Sonne, C., Rosing-Asvid, A., Hansen, M., Provatas, A. and McKinney, M. A. (2017) Blubberdepth distribution and bioaccumulation of PCBs and organochlorine pesticides in Arctic-invading killer whales. Science of the Total Environment, 601–602, 237–246. https ://doi.org/10.1016/j.scito tenv.2017.05.193.
Pitman, R. L. and Ensor, P. (2003). Three forms of killer whales (Orcinus orca) in Antarctic waters. Journal of Cetacean Research and Management, 5(2), 131-140. https://archive.iwc.int/pages/search.php?search=%21collection15&k=
Poncelet, E., Barbraud, C. and Guinet, C. (2010). Population dynamics of killer whales (Orcinus orca) in the Crozet Archipelago, southern Indian Ocean: a mark-recapture study from 1977 to 2002. Journal of Cetacean Research and Management, 11, 41–48. https://archive.iwc.int/pages/search.php?search=%21collection15&k=
Reeves, R. R. and Mitchell, E. (1988). Distribution and seasonality of killer whales in the eastern Canadian Arctic. Rit Fiskideildar, 11, 136-160.
Reid, J. B., Evans, P. G. H. and Northridge, S. P. (2003). Atlas of cetacean distribution in North-west European waters. Peterborough: Joint Nature Conservation Committee.
Reinhart, N. R., Ferguson, S. H., Koski, W. R., Higdon, J. W., LeBlanc, B., Tervo, O. and Jepson, P. D. (2013). Occurrence of killer whale Orcinus orca rake marks on Eastern Canada-West Greenland bowhead whales Balaena mysticetus. Polar biology, 36(8), 1133-1146. https://doi.org/10.1007/s00300-013-1335-3
Ross, P. S., Ellis, G. M., Ikonomou, M. G., Barrett-Lennard, L. G. and Addison, R. F. (2000). High PCB concentrations in free-ranging Pacific killer whales, Orcinus orca: effects of age, sex and dietary preference. Marine Pollution Bulletin, 40(6), 504-515. https://doi.org/10.1016/S0025-326X(99)00233-7
Samarra, F. I. P., Deecke, V. B. and Miller, P. J. O. (2016). Low-frequency signals produced by northeast Atlantic killer whales (Orcinus orca). Journal of the Acoustical Society of America 139, 1149–1157. https://doi.org/10.1121/1.4943555
Samarra, F. I. P. and Foote, A. D. (2015). Seasonal movements of killer whales between Iceland and Scotland. Aquatic Biology, 24(1), 75-79. https://doi.org/10.3354/ab00637
Samarra, F. I. P., Fennell, A., Aoki, K., Deecke, V. B. and Miller, P. J. (2012). Persistence of skin marks on killer whales (Orcinus orca) caused by the parasitic sea lamprey (Petromyzon marinus) in Iceland. Marine Mammal Science, 28(2), 395-401. https://doi.org/10.1111/j.1748-7692.2011.00486.x
Samarra, F. I. P., Deecke ,V. B., Vindin,g K., Rasmussen, M.H., Swift, R. and Miller, P. J. O. (2010). Killer whales (Orcinus orca) produce ultrasonic whistles. Journal of the Acoustical Society of America, 128, EL205–EL210. https://doi.org/10.1121/1.3462235
Sergeant, D. E. and Fisher, H. D. (1957). The smaller Cetacea of eastern Canadian waters. Journal of the Fisheries Board of Canada, 14(1), 83-115. https://doi.org/10.1139/f57-003
Sigurjónsson, J. and Leatherwood, S. (1988) The Icelandic live-capture fishery for killer whales, 1976–1988. Rit Fiskideildar, 11, 307– 316.
Sigurjónsson, J., Lyrholm, T., Leatherwood, S., Jónsson, E. and Víkingsson, G. A. (1988). Photoidentification of killer whales, Orcinus orca, off Iceland, 1981 through 1986. Rit Fiskideildar, 11, 99–114.
Similä, T. (1997). Sonar observations of killer whales (Orcinus orca) feeding on herring schools. Aquatic Mammals, 23, 119-126.
Similä, T., Holst, J. C. and Christensen, I. (1996). Occurrence and diet of killer whales in northern Norway: seasonal patterns relative to the distribution and abundance of Norwegian spring-spawning herring. Canadian Journal of Fisheries and Aquatic Sciences, 53(4), 769-779. https://doi.org/10.1139/f95-253
Similä, T. and Ugarte, F. (1993). Surface and underwater observations of cooperatively feeding killer whales in northern Norway. Canadian Journal of Zoology, 71(8), 1494-1499. https://doi.org/10.1139/z93-210
Simon, M., McGregor, P. K. and Ugarte, F. (2007). The relationship between the acoustic behaviour and surface activity of killer whales (Orcinus orca) that feed on herring (Clupea harengus). Acta Ethologia, 10, 47–53. https://doi.org/10.1007/s10211-007-0029-7
Simon, M., Wahlberg, M., Ugarte, F. and Miller, L. A. (2005). Acoustic characteristics of underwater tail slaps used by Norwegian and Icelandic killer whales (Orcinus orca) to debilitate herring (Clupea harengus). Journal of Experimental Biology, 208, 2459-2466. https://doi.org/10.1242/jeb.01619
Storrie, L., Lydersen, C., Andersen, M., Wynn, R. B. and Kovacs, K. M. (2018). Determining the species assemblage and habitat use of cetaceans in the Svalbard archipelago, based on observations from 2002 to 2014. Polar Research, 37, 1463065. https ://doi.org/10.1080/17518369.2018.1463065
Strager, H. (1995). Pod-specific call repertoires and compound calls of killer whales, Orcinus orca, in the waters of northern Norway. Canadian Journal of Zoology, 73, 1037–1047. https://doi.org/10.1139/z95-124
Tavares, S. B., Samarra, F. I. and Miller, P. J. (2016). A multilevel society of herring-eating killer whales indicates adaptation to prey characteristics. Behavioral Ecology, 28(2), 500-514. https://doi.org/10.1093/beheco/arw179
Ugarte, F., Simon, M., Laidre, K. and Rosing-Asvid, A. (2013). Recent increase of catches of killer whales in Southeast Greenland – Is there a need for NAMMCO advice? Document NAMMCO SC/20/20 presented to the 20th Scientific Committee of NAMMCO (13 – 16 November), Reykjavik, Iceland. 5pp. https://nammco.no/topics/scientific-committee-reports/
Vester, H. and Hammerschmidt, K. (2013). First record of killer whales (Orcinus orca) feeding on Atlantic salmon (Salmo salar) in northern Norway suggest a multi-prey feeding type. Marine Biodiversity Records, 6, E9. https://doi.org/10.1017/S1755267212001030
Víkingsson, G. A. (2004). Hahyrningur. In Hersteinsson, P. (ed.), Islensk spendyr (pp. 166-171). Reykjavik: Vaka-Helgafell.
Vongraven, D. and Bisther, A. (2014). Prey switching by killer whales in the north-east Atlantic: observational evidence and experimental insights. Journal of the Marine Biological Association of the United Kingdom, 94(06), 1357-1365. https://doi.org/10.1017/S0025315413001707
Ward, E. J., Holmes, E. E. and Balcomb, K. C. (2009). Quantifying the effects of prey abundance on killer whale reproduction. Journal of Applied Ecology, 46(3), 632-640. https://doi.org/10.1111/j.1365-2664.2009.01647.x
Weir, C. R. (2002). Killer whales in British waters. British Wildlife, 14, 106-108.
Whitehead, H. and Glass, C. (1985). Orcas (killer whales) attack humpback whales. Journal of Mammalogy, 66(1), 183-185. https://doi.org/10.2307/1380982
Witting, L. (2019). Rebuttal against Desforges et al. (2018): No evidence for a global killer whale population collapse. Marine Mammal Science, 35(3), 1197-1200. https://doi.org/10.1111/mms.12599
Wolkers, H., Corkeron, P. J., Van Parijs, S. M., Similä, T. and Van Bavel, B. (2007). Accumulation and transfer of contaminants in killer whales (Orcinus orca) from Norway: indications for contaminant metabolism. Environmental Toxicology and Chemistry, 26(8), 1582-1590. https://doi.org/10.1897/06-455R1.1
Young, B. G., Higdon, J. W. and Ferguson, S. H. (2011). Killer whale (Orcinus orca) photo-identification in the eastern Canadian Arctic. Polar Research, 30, 7203. https://doi.org/10.3402/polar.v30i0.7203
Øien, N. (1993). Abundance of killer whales (Orcinus orca) in waters off Norway. Bergen, Norway (unpublished).
Øien, N. (1990). Sightings surveys in the northeast Atlantic in July 1988: distribution and abundance of cetaceans. Reports of the International Whaling Commission 40, 499-511.
Øien, N. (1988). The distribution of killer whales (Orcinus orca) in the North Atlantic based on Norwegian catches, 1938-1981, and incidental sightings, 1967–1987. Rit Fiskideildar, 11, 65–78.