Killer whale

Updated: July 2018

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 while colouring pattern. The body is largely black dorsally and white ventrally. Behind the eyes are noticeable oval white patches, referred to as eye patch. Behind the rear base of the dorsal fin is a grey patch 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.

Killer whale sightings during North Atlantic Sightings Surveys from 1987-2015. Not all areas were surveyed each year.
killerwhale_assessment_table

ABUNDANCE

Estimated to be around 15,000 for the whole North Atlantic from the North Atlantic Sightings Survey (NASS) in 2001.

DISTRIBUTION

Found worldwide, and widespread throughout the North Atlantic. Likely more abundant in the northeast Atlantic versus the northwest Atlantic. Low numbers observed in West Greenland.

RELATION TO HUMANS

Killer whales are popular animals for whalewatching activities. Hunted opportunistically in Greenland.

CONSERVATION AND MANAGEMENT

NAMMCO provides advice to the member countries on conservation status, and hunting in Greenland.

© Norwegian Orca Survey

© Fernando Ugarte

Latin: Orcinus orca
Faroese: Bóghvítuhvalir / Mastrarhvalir
Icelandic: Háhyrningur
Greenlandic: Aarluk
Norwegian: Spekkhogger, staurhval
Danish: Spækhugger
English: Killer whale, Orca

Lifespan

Females average about 50 years (but oldest known female in the wild was estimated to be 105 years old)

Males average about 30 years (with maximum of about 60 years)

Average Size

Females: up to 8.5 meters in length, maximum weight of 7.5 tons

Males: up to 10 meters in length, and can weigh 10 tons

The size of killer whales also varies greatly regionally

Migration and Movements

Killer whales movements seem mainly to be associated with the movement of their prey. Some long distance movements have been documented, but they do not have a “migration” in the North Atlantic per se

Feeding

As a species, they are considered a generalist predator with a diverse diet that includes bony fish, sharks, pinnipeds, other cetaceans, seabirds, reptiles and squids. However, some groups of killer whales can become specialists for certain prey, with adaptive behaviours for that prey

© Fernando Ugarte

At Sea

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 reaches easily 3 meters high, the black erect fin is the first discernable clue at sea. Killer whales are commonly found in groups.

Physical appearance

Sexual dimorphism is highly discernible in killer whales, both in terms of body length and size of the dorsal fin. When mature, male killer whales can reach up to 10 meters and weigh a maximum of 10 tons whereas females can reach 8.5 meters with a maximum weight of 7.5 tons, although the size of killer whales varies greatly regionally. 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.

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 while colouring pattern. The body is largely black dorsally and white ventrally. Behind the eyes are noticeable oval white patches, referred to as eye patch. Behind the rear base of the dorsal fin is a grey patch 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.

Although killer whales are currently considered a single species, evidence has suggested a more complex situation with potential separate species status. 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 and Ensor, 2003; Morin et al., 2010; Foote et al., 2016). In the North Atlantic, the occurrence of two disparate types was suggested. The generalist type 1 could be feeding on diverse prey types, with the diet of certain groups including both fish and mammal-prey, whereas the specialist type 2 would be highly specialized on baleen whales (Foote et al., 2009).

Behaviour

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 kph, and they are able to maintain brief swimming speeds of 45 kph. 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 meters when foraging.

killer whale breaching
Breaching killer whale © Eve Jourdain / Norwegian Orca Survey
spyhopping killer whale
Spyhopping killer whale © Eve Jourdain / Norwegian Orca Survey
lobtailing killer whale
Lobtailing killer whale © Eve Jourdain / Norwegian Orca Survey

Social organization

Pod of killer whales © Eve Jourdain / Norwegian Orca Survey

Killer whales are highly social and group-living animals. But importantly, social organisation and behaviours greatly vary with prey types hunted and ecology. The main stable unit is a matriline, in which the oldest female (referred to as 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, and so 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 of individuals (Bigg et al., 1990).

Sound and communication

Killer whales’ primary sense is the auditory system. Three main types of sound including echolocation clicks, whistles and calls are used. 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 but also to navigate and locate 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 kms. 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).

 

Reproduction

Female killer whales typically give birth to their first viable offspring at 12-14 years of age after a gestation of 17-18 months. Calves are nursed for 1 to 2 years, gradually including solid food into their milk diet. Females produce in average 4 to 5 calves throughout their reproductive lifespan. When they reach approximately 45 years of age, females become post-reproductive but may live up to 80 years.

Males become sexually mature at about 15 years of age, after what the dorsal fin grows substantially. Males appear to have a shorter life expectancy, which is in average 30 years.

Importantly, due to late sexual maturity, low calf production per female and a prolonged post-reproductive phase, the potential for population growth and recovery remains low.

Killer whale with calf © Fernando Ugarte

Diet and feeding behaviour

The killer whale, as a species, is considered as a generalist predator with a diverse diet that includes bony fish, sharks, pinnipeds, other cetaceans, seabirds, reptiles and squids (Ford, 2009). However, local populations may display strong prey preferences for which they develop specific feeding strategies and adapt behaviours. A well known example is about 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 is exclusively fish-eating, preferentially feeding on salmon species, the transient killer whales entirely specialise on marine mammal prey (Baird and Dill, 1995; Ford and Ellis, 1998).

In the North Atlantic Ocean, killer whales also include a wide range of prey species. In Atlantic Canada, prey taken includes: baleen whales such as humpback whales (Megaptera novaenagliae) and minke whales (Balaenoptera acutorostrata); toothed cetaceans such as beluga whales (Delphinapterus leucas) and white-beaked dolphins (Lagenorhynchus albirostris);  pinnipeds; seabirds; herring and tuna (Sergeant and Fisher, 1957; Whitehead and Glass, 1985; Lawson et al., 2007). Whether these killer whales are generalist feeders or display group-specific prey specialisations remains unknown.

In contrast with killer whales from Greenland and Newfoundland-Labrador, where evidence suggested both fish and marine mammal prey, only marine mammals were reported as being part of the Canadian Arctic killer whale diet so far. Their diet regularly includes harp seal (Pagophilus groenlandicus), ringed seal (Pusa hispida), bearded seal (Erignathus barbatus), harbour seal (Phoca vitulina), hooded seal (Cystophora cristata), narwhal (Monodon monoceros), beluga whale and bowhead whale (Balaena mysticetus) (Reeves and Mitchell, 1988; Ferguson et al., 2012 a and b; Higdon et al., 2012). Nevertheless, predation on fish cannot be ruled out.

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), Greenland halibut (Reinhardtius hippoglossoides) but also cephalopods (see Jensen and 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 the 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 as a tight school below the sea surface, before debilitating the prey with underwater tail-slaps and consuming herring one by one (Simila and Ugarte, 1993; Similä, 1997; Simon et al., 2005; video 1). However, confirmed observations of killer whales preying on seabirds, grey seals (Halichoerus grypus) and minke whales were also reported 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 and Foote, 2015).

Other prey items documented for Norwegian killer whales include cod, squids, bottlenose whales, mackerel, Atlantic salmon (Salmo salar), pinnipeds and seabirds (Jonsgård, 1968; Vester and Hammerschmidt, 2013; Vongraen and 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, as for the mackerel fisheries between Scotland and Norway and for the herring fisheries off northern Norway. Yet, much remains to be discovered about potential prey specialisations and local feeding behaviours in the North Atlantic.

killer whales herring fishing
Killer whales feeding near herring fishing boat © Eve Jourdain / Norwegian Orca Survey

Distribution and habitat

Killer whales are cosmopolitan, ranging in all the world’s oceans, and they are increasingly abundant in high latitude productive waters (Leatherwood and Dahlheim, 1978; Forney and 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 (e.g. Sigurjónsson and Leatherwood, 1988; Similä et al., 1996).

Distribution in the North Atlantic

Killer whales widely range from the east coast of Canada to Norwegian waters. More specifically, they occur all along the eastern Canadian coast, from the Bay of Fundy and north to the Arctic (Sergeant and Fisher, 1957; Whitehead and Glass, 1985; Lien et al., 1988; Reeves and Mitchell, 1988), although they are more common in the Newfoundland and Labrador regions. They 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. Historically, killer whales were known to occur in Canadian Arctic regions such as Davis Straight and Baffin Bay (Reeves and 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 and Ferguson, 2009). 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). 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). Off the coast of the UK, the Northern Isles and north-east of Scotland, killer whales are also regularly sighted (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 and Foote, 2015).  An 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). Killer whales occur all along the Norwegian coast, with the main concentrations off northern Norway and Finnmark.

Even though long-distance movement was documented (over 5000 km travelled in a month; Matthews et al., 2011), no evidence for migration in the North Atlantic was brought so far.

Killer whale sightings during North Atlantic Sightings Surveys from 1987-2015. Not all areas were surveyed each year.

Stock definition

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. But recent efforts dedicated to describing populations have greatly improved our understanding of the species. As such, extensive studies conducted off Iceland, Norway and UK-Scotland, resulting in over 1,000 individual killer whales identified across the north-east Atlantic and a comparison of identification catalogues revealed site fidelity at several locations with distinct populations largely associated with particular prey resources (Foote et al., 2010).

Populations and management units

In the northeast Atlantic, three distinct killer whale populations have been suggested based on their  association their major prey source: 1) the Atlantic herring population (including killer whales from the North Sea, Iceland and Norway), 2) the northeast Atlantic mackerel population, and 3) the eastern stock of the Atlantic bluefin tuna (Thunnus thynnus) population (Foote et al., 2011).

Killer whales around Iceland © Fernando Ugarte

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 an indicator of population structure and management units. 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, and are associated with the north-east Atlantic mackerel stock during autumn (Luque et al., 2006; Foote et al., 2010). Off the Northern Isles and the north-east 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 and 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 a possibility of several populations ranging in the western Atlantic, or one large and widespread population.

The main management issue lies in the fact that real baseline data on killer whale abundance, distribution and population structure in this region is still missing (Higdon, 2007). For effective management of the species, further data are needed and biopsy sampling for genetic analyses could assist in assessing management units and possible movement between Canadian Arctic/Atlantic and Greenland (Higdon, 2007).

Total abundance in the North Atlantic

Killer whales are largely distributed throughout the North Atlantic but densities greatly vary among locations, presumably in relation with variations in resource distribution and possibly due to former removals that may have negatively impacted population size. Numerous abundance estimates were produced at different scales for North eastern Atlantic waters. As such, 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 to the NSS stock of herring and estimated this sub-population to count 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 and Wade, 2006). No abundance estimate currently exists for the Northwest Atlantic but based on available data, it was suggested that the north-west Atlantic population is not as large as the north-eastern Atlantic (Lawson and Stevens, 2014).

Abundance in different areas

Atlantic and Arctic Canada

Due to a relatively large study area combined to a little observer coverage and a systematic effort in monitoring killer whale occurrence only recently established, 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 was 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.

Greenland

Killer whales do not appear to be abundant in Greenlandic waters, as suggested by very few sightings on 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).

Iceland

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 and 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).

UK-Scotland

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 NE Atlantic, it is likely that available abundance estimates include killer whales from UK waters as well (Samarra and Foote, 2015).

Norway

Various abundance estimates were provided for killer whales off the Norwegian coast. Christensen (1988) estimated that at least 1,500 killer whales could be using Norwegian coastal waters when the herring over-winters close to shore. The North Atlantic Sighting Survey (NASS) later provided an estimate of 7,000 killer whales ranging in Norwegian waters (Øien, 1993), although these whales likely belong to several populations.

Long-term photo-identification studies enabled to catalogue a minimum of 686 individual killer whales occurring in the winter herring ground from 1986-2005 and 2007-2013 and a total abundance estimate of about 1,000 individuals was suggested (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 coastal waters of northern Norway (Jourdain and Karoliussen, 2016).

Changes in trends

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. In Hudson Bay, a marked climate shift has resulted in a drastic decrease in both extent and duration of sea ice. Since the 1950’s, killer whale sightings have dramatically increased in Hudson Bay, with possibly yearly visits from the 1980s, presumably in relation to a longer ice-free season that provides a suitable open water habitat (Gagnon and Gough 2005; Higdon, 2007; Higdon and 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; video 2). Concerns for the recovery of the Eastern Canada-Western Greenland bowhead whales have been raised (Reinhart et al., 2013).

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° (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.

Western Atlantic

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.

Eastern Atlantic

Killer whales in the North-eastern Atlantic appear to be associated to specific prey resources and three distinct populations were suggested (Foote et al., 2009). However, due to a small sample size relative to high abundance estimates and poorly understood movement patterns across the Atlantic, delineation of management units yet 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).

Management

NAMMCO provides management advice to Norway, Iceland, Greenland, and the Faroe Islands 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.”

Direct catches

Reported killer whale catches in Greenland from 2002. Data from the National Progress Reports.

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 (gap in data for 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 regular hunting activity. No regulations for killer whale hunting currently exist in Greenland, and conservation related questions have been raised (Ugarte et al., 2013).

Killer whale hunting in Norway dates as far back as 1920, but catches were recorded only from 1938 (Bloch and Allison, 2005). After licensing of small-type whaling was introduced in Norway in 1938, all killer whale catches were required to be reported, and the logbook counted 2,435 killer whales caught from 1938 to 1981 (Øien, 1988). In 1982, killer whale became protected by the 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 Aboriginal subsistence remains permitted, based on the importance of whales as a food source and for the culture of Aboriginal communities (Higdon, 2007). However, lethal interactions with fisheries may still occur, as suggested by a photographed recently taken of a killer whale calf displaying a bullet wound on its head (Lawson et al., 2007).

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, 181 off East and Southern Greenland. Although the target species of whaling operations was the minke whale, other cetaceans such as killer whale 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).

Live-capture fisheries

Fifty-nine (1976-1988; Sigurjónsson and Leatherwood, 1988) and 64 (1960-1983; Bloch and Lockyer, 1988) killer whales were live-captured 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). 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).

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 specialisations 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 could greatly lead entire groups and/or populations to a sharp decline or even extinction (Matkin et al., 2008).

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 documented between Scotland and Norway with the mackerel and herring fisheries (Luque et al., 2006). 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, while killer whales commonly associate with the commercial herring trawlers during the winter months, several cases of killer whales trapped in purse seine nets were recorded.

© Norwegian Orca Survey

Greenland

The Greenland Institute of Natural Resources (GINR) occasionally conducts interview-related surveys among hunters and collect biological samples on killer whale catches. Even though data are opportunistically collected, preliminary results showed that killer whale hunting that was historically a rare activity, has become a more important game species 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.

Iceland

The Marine and Freshwater Research Institute 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, behaviours, feeding ecology and levels of contamination.

Norway

During line-transect surveys dedicated to monitor cetacean abundance across the Norwegian Sea during the summer months, the Institute of Marine Research (Bergen, Norway) records killer whale occurrence and produce updated data about killer whale distribution and abundance in these waters (e.g. Nøttestad et al., 2015).

Norwegian Orca Survey (Andenes, Norway), a non-profit research organisation established in 2013, is dedicated to long-term monitoring of killer whales occurring off northern Norway. Main goals consist in studying population abundance, foraging ecology and habitat use. The ongoing research also aims at continuing the photo-identification study initiated by colleagues in 1986 (Similä et al., 1996; Vongraven and Bisther, 2013).

The Arctic University of Norway (UiT, Tromsø, Norway) has conducted tagging experiments on killer whales during the winter months in 2015-2017.

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.

References

Baird, R. W., & 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.


Beck, S., Foote, A. D., Kötter, S., Harries, O., Mandleberg, L., Stevick, P. T., … & Durban, J. W. (2014). Using opportunistic photo-identifications to detect a population decline of killer whales (Orcinus orca) in British and Irish waters. Marine Biological Association of the United Kingdom. Journal of the Marine Biological Association of the United Kingdom, 94(6), 1327.


Beck, S., Kuningas, S., Esteban, R., & Foote, A. D. (2012). The influence of ecology on sociality in the killer whale (Orcinus orca). Behavioral Ecology, 23(2), 246-253.


Bigg, M. A., Olesiuk, P. F., Ellis, G. M., Ford, J. K. B., & Balcomb, K. C. (1990). Social organization and genealogy of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Report 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 Fisk.. 11: 55-64.


Bolt, H. E., Harvey, P. V., Mandleberg, L., & 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.


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. Available at http://www.sararegistry.gc.ca/status/status_e.cfm.


Deecke, V. B., Nykänen, M., Foote, A. D., & Janik, V. M. (2011). Vocal behaviour and feeding ecology of killer whales Orcinus orca around Shetland, UK. Aquatic Biology, 13(1), 79-88.


Ferguson, S. H., Higdon, J. W., & 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.


Ferguson, S. H., Kingsley, M. C., & Higdon, J. W. (2012b). Killer whale (Orcinus orca) predation in a multi-prey system. Population Ecology, 54(1), 31-41.


Ferguson, S. H., Higdon, J. W., & Chmelnitsky, E. G. (2010). The rise of killer whales as a major Arctic predator. In A Little Less Arctic (pp. 117-136). Springer Netherlands.


Foote, A. D., Vijay, N., Ávila-Arcos, M. C., Baird, R. W., Durban, J. W., Fumagalli, M., … & Robertson, K. M. (2016). Genome-culture coevolution promotes rapid divergence of killer whale ecotypes. Nature communications, 7.


Foote, A. D., Newton, J., Ávila-Arcos, M. C., Kampmann, M. L., Samaniego, J. A., Post, K., … & 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.


Foote, A. D., Vilstrup, J. T., De Stephanis, R., Verborgh, P., Abel Nielsen, S. C., Deaville, R., … & Pérez-Gil, M. (2011). Genetic differentiation among North Atlantic killer whale populations. Molecular Ecology, 20(3), 629-641.


Foote, A.D., Similä, T., Víkingsson, G.A., Stevick, P.T. (2010) Movement, site fidelity and connectivity in a top marine predator, the killer whale. Evolutionary Ecology, 24, 803–814.


Foote, A. D., Newton, J., Piertney, S. B., Willerslev, E., & Gilbert, M. T. P. (2009). Ecological, morphological and genetic divergence of sympatric North Atlantic killer whale populations. Molecular Ecology, 18(24), 5207-5217.


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.


Ford, J. K. B. (2009). Killer whales Orcinus orca. Pages 650-657 in W. F. Perrin, B. Würsig, and J. G. M. Thewissen, editors. The encyclopedia of marine mammals. Academic Press, San Diego, USA.


Ford, J. K., Ellis, G. M., Barrett-Lennard, L. G., Morton, A. B., Palm, R. S., & 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.


Ford JKB (1991) Vocal traditions among resident killer whales (Orcinus orca) in coastal waters of British Columbia. Can J Zool 69:1454–1483.


Forney, K. A., & Wade, P. R. (2006). Worldwide distribution and abundance of killer whales. Whales, whaling and ocean ecosystems, 145-162.


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.


Gunnlaugsson, T., & 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 and Donovan 1988. Aerial survey of cetaceans in the coastal waters of Iceland, June-July 1986. Rep. Int. Whal. Commn 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., & 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.


Higdon, J. W., & 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.


Higdon, J. (2007). Status of knowledge on killer whales (Orcinus orca) in the Canadian Arctic. Canadian Science Advisory Secretariat= Secrétariat canadien de consultation scientifique.


Huse, G., Fernö, A., & 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.


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 | DOI: 10.1038/srep18573 1. 17pp.


Jonsgård, A. (1968). A note on the attacking behaviour of the killer whale (Orcinus orca). Norsk Hvalfangst-Tidende, 57, 84-85.


Jourdain E. and Karoliussen R. (2016). The Norwegian Orca ID-Catalogue. doi: 10.6084/m9.figshare.4205226.


Kuningas, S., Similä, T., & 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.


Laidre, K. L., Heide-Jørgensen, M. P., & 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.


Lawson, J. W., & 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.


Lawson, J. W., Stevens, T. S., & 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., & Dahlheim, M. E. (1978). Worldwide distribution of pilot whales and killer whales. Naval Ocean Systems Center. Tech. Rep. 443: 1-39.


Lien, J., Stenson, G. B., & 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., & 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.


Matkin, C. O., Saulitis, E. L., Ellis, G. M., Olesiuk, P., & 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.


Matthews, C. J., Luque, S. P., Petersen, S. D., Andrews, R. D., & 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.


Morin, P. A., Archer, F. I., Foote, A. D., Vilstrup, J., Allen, E. E., Wade, P., … & Bouffard, P. (2010). Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome research, 20(7), 908-916.


Nøttestad, L., Krafft, B. A., Anthonypillai, V., Bernasconi, M., Langård, L., Mørk, H. L., & Fernö, A. (2015). Recent changes in distribution and relative abundance of cetaceans in the Norwegian Sea and their relationship with potential prey.


Nøttestad, L., Sivle, L. D., Krafft, B. A., Langård, L., Anthonypillai, V., Bernasconi, M., … & 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.


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. Rep. Int. Whal. Commn. 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.


Reeves, R. R., & Mitchell, E. (1988). Distribution and seasonality of killer whales in the eastern Canadian Arctic. Rit Fiskideildar, 11, 136-160.


Samarra, F. I. P., & Foote, A. D. (2015). Seasonal movements of killer whales between Iceland and Scotland. Aquatic Biology, 24(1), 75-79.


Samarra, F. I., Fennell, A., Aoki, K., Deecke, V. B., & 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.


Samarra FIP, Deecke VB, Vinding K, Rasmussen MH, Swift R, Miller PJO (2010) Killer whales (Orcinus orca) produce ultrasonic whistles. Journal of the Acoustical Society of America, 128, EL205–EL210.


Sergeant, D. E., & Fisher, H. D. (1957). The smaller Cetacea of eastern Canadian waters. Journal of the Fisheries Board of Canada, 14(1), 83-115.


Sigurjónsson J, 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, Víkingsson GA (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., & 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.


Similä, T., & Ugarte, F. (1993). Surface and underwater observations of cooperatively feeding killer whales in northern Norway. Canadian Journal of Zoology, 71(8), 1494-1499.


Simon M, McGregor PK, 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.


Simon, M., Wahlberg, M., Ugarte, F. & 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.


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.


Tavares, S. B., Samarra, F. I., & Miller, P. J. (2016). A multilevel society of herring-eating killer whales indicates adaptation to prey characteristics. Behavioral Ecology, arw179.


Pitman, R. L., & Ensor, P. (2003). Three forms of killer whales (Orcinus orca) in Antarctic waters. Journal of Cetacean Research and Management, 5(2), 131-140.


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.


Reid J.B., Evans P.G.H., Northridge S.P., 2003, Atlas of cetacean distribution in North-west European waters. Joint Nature Conservation Committee, Peterborough.


Reinhart, N. R., Ferguson, S. H., Koski, W. R., Higdon, J. W., LeBlanc, B., Tervo, O., & 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.


Ross, P. S., Ellis, G. M., Ikonomou, M. G., Barrett-Lennard, L. G., & 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.


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 2013, Reykjavik, Iceland. 5pp.


Vester, H., & 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.


Víkingsson GA (2004) Hahyrningur. In: Hersteinsson P (ed) Islensk spendyr, Vaka-Helgafell, Reykjavık, pp 166–171


Vongraven, D., & 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.


Ward, E. J., Holmes, E. E., & Balcomb, K. C. (2009). Quantifying the effects of prey abundance on killer whale reproduction. Journal of Applied Ecology, 46(3), 632-640.


Weir CR (2002) Killer whales in British waters. Br Wildl 14:106 – 108


Whitehead, H., & Glass, C. (1985). Orcas (killer whales) attack humpback whales. Journal of Mammalogy, 66(1), 183-185.


Wolkers, H., Corkeron, P. J., Van Parijs, S. M., Similä, T., & 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.


Young, B. G., Higdon, J. W., & Ferguson, S. H. (2011). Killer whale (Orcinus orca) photo-identification in the eastern Canadian Arctic. Polar Research, 30.

Start typing and press Enter to search