European regional assessment: Least Concern (LC)

Current abundance estimates of killer whales in European waters suggest they number in the 10s of thousands and they are widely distributed throughout the Atlantic Ocean. Killer whales therefore do not qualify for a threatened category under criteria B (geographic range), C (small population size and decline) or D (very small or restricted population). The relevant IUCN Red List criterion for this species is therefore category A (population size reduction).

Killer whales have an estimated generation period of 24 years, the three-generation assessment period is therefore the 72-years from 1950 and 2022. There are no trend data available for killer whales in European waters during this time or historical abundance estimates for comparison to recent estimates. During the assessment period, European killer whales have been subjected to hunts, culls, and live capture to supply aquaria. With the exception of ongoing subsistence hunt off Greenland this direct exploitation has ceased in European waters.

The highest level of exploitation was from Norwegian whalers that took 2435 killer whales between 1938 and 1981 (Vongraven and Bisther 1995). Between 1976 and 1988, 59 were taken as live capture from Icelandic waters (Sigurjónsson and Leatherwood 1988). This historic level of anthropogenic removal, however, is not sufficient to suggest or infer a reduction of the European population by 50% required under A1d to be assessed as Vulnerable.

Ongoing threats such as high contaminate burden, prey depletion and habitat degradation are cause for concern and are of critical importance for some small subpopulations of European Killer whales (e.g. UK and Gibraltar). However, there is no evidence to suggest or infer that these threats have resulted or will result in a reduction of the total population size of European killer whales by 30%, the threshold required for Vulnerable under A2, 3 or 4.

The current global and previous European regional assessment for killer whales is Data Deficient based on taxonomic uncertainties and the potential for ongoing decline, respectively. Under the current Red List Guidelines (Version 15.1, 2022), Data Deficient is to be applied when there is insufficient evidence to determine between Critically Endangered and Least Concern. As there is sufficient data to reject the possibility that European killer whales could be classified as Critically Endangered and there is no evidence for any threatened category, the European regional assessment for killer whales is Least Concern.

The Gibraltar killer whale subpopulation has been previously assessed as is Critically Endangered (C2a(i,ii); D) (Esteban and Foote 2019).

Killer Whales have a cosmopolitan distribution and are found in all the World’s oceans from polar to equatorial latitudes. Within European waters, they occur throughout the Barents Sea, off East Greenland, around Iceland and the Faroe Islands, and offshore in deep waters of the North Atlantic. They occur all along the Norwegian coast and are seasonal visitors to Svalbard (Storrie et al. 2018). They also occur off the British Isles, specifically Orkney and Shetland and the northwestern North Sea. There is also a small subpopulation that occupies waters off the west coast of Scotland and around Ireland (Beck et al. 2014). Further South there are Killer Whales off Gibraltar and the Canary Islands. The species is considered vagrant in the Mediterranean Sea (Mrusczok et al. 2022).

Within the North Atlantic, genetic analysis supports the delineation of three putative subpopulations of Killer Whales (termed A, B and C), that are defined by their association with specific fish stocks (Foote et al. 2011). Subpopulations A and B occupy the northern waters of the North Atlantic and are associated with Herring (Clupea harengus) and Mackerel (Scomber scombrus) stocks, respectively. Samples for genetic analysis have been collected from population A individuals from Norway, Iceland, and East Scotland, and subpopulation B individuals from Iceland, Ireland, and Scotland. There is evidence of male-mediated gene flow between subpopulations A and B (Foote et al. 2011). Harvested Killer Whales off East Greenland were also allocated to subpopulation A, suggesting either a recent divergence in these subpopulations or continued gene flow (Foote et al. 2013). Population C is considered allopatric to population A, with these two populations showing the most genetic separation. Subpopulation C is associated with Atlantic Blue Fin Tuna (Thunnus thynnus) and included individuals sampled further south, off the Canary Islands and Gibraltar (Foote et al. 2011, Esteban et al. 2014). Killer whales from Gibraltar and the Canary Islands are considered genetically distinct with no female-mediated gene flow (Esteban et al. 2016c).

Photoidentification of killer whales off Iceland and Norway suggests further structuring of population A, with separation between killer whale communities associated with Icelandic summer-spawning herring and Norwegian spring-spawning herring stocks, as there were no matches between these groups of animals (Foote et al. 2010). It is possible that the collapse of the Norwegian Herring stocks in the 1970s resulted in the isolation of these communities and with the recovery of these stocks connectivity between these communities may be re-established and requires further research (Jourdain et al. 2019).

Two ecotypes of Killer Whales have been suggested for the North Atlantic that separates generalist feeders and marine mammal eaters, termed type I and II, similar to ecotypes identified in the Pacific and Southern oceans (Foote et al. 2009). This was based on molecular analysis, morphology, and teeth wear. However, the authors of the original study have recently suggested that this distinction of ecotypes in the North Atlantic is no longer valid (Foote 2022).

North Atlantic Sightings Surveys (NASS) have estimated abundance for six separate years between 1987 and 2015 (Pike et al. 2019) and are as follows: 8,899 (CV 0.46) in 1987; 10,316 (CV 0.37) in 1989; 4,736 (CV 0.48) in 1995; 20,345 (CV 0.63) in 2001; 57,460 (0.50) from surveys in 2015 that included a larger survey area that extended further north into the Norwegian Sea; and 30,540 (CV 0.63) in 2015. Low precision in these yearly estimates prevents trend analysis. The most recent Norwegian shipboard line-transect surveys of the Northeast Atlantic, conducted over a 5-year period (2014 – 2018) resulted in an estimate of 15,056 (CV=0.29) killer whales (Leonard and Øien 2020a). Previous estimates from Norwegian shipboard surveys were 9,563 (CV 0.36) and 18,821 (CV 0.24) for the periods of 2008–2013 and 2002–2007, respectively (Leonard and Øien 2020b). Killer whales were not regularly sighted during the SCANS I, II and III surveys (Hammond et al. 2017, Hammond et al. 2013, Hammond et al. 2002).

In contrast, the number of killer whales off Gibraltar and the Canary Islands is considerably fewer, there are no available point sampling estimates, but minimum counts are 47 and 16 individuals for each location, respectively (Esteban et al. 2016c).

Killer Whales are apex predators that as a species take a range of different prey types from schooling fish to baleen whales (Jefferson et al. 1991, Ford and Ellis 2006, Pitman and Durban 2010). Although as a species they are generalist predators, at population and community levels they can show highly specialised hunting techniques and behaviours which may limit the prey species taken at individual levels (Saulitis et al. 2000). These specialised hunting techniques include beaching to catch pinnipeds off Patagonia (Lopez and Lopez 1985) and causing waves that knock seals from ice flows in the Antarctic (Visser et al. 2008); Within European waters, Killer Whales off Norway coordinate to drive Herring schools from deep water to the ocean surface to allow for easier capture, and stun with tail slaps (Domenici et al. 2000, Nøttestad et al. 2002). Differences in foraging technique can even be observed at community levels within small populations, this is exemplified by pods off Gibraltar that either depredate from long line fisheries and those that do not (Esteban et al. 2016a).

Within European waters there is growing evidence that Killer Whales that feed on fish also take marine mammals such as seals, with dietary specialisation being a gradient rather than distinct ecotypes as is seen in the North Pacific with transient, resident, and offshore ecotypes (Jourdain et al. 2020, Remili et al. 2021). Off Greenland, Killer Whales feed multiple prey species but are thought to feed predominantly on marine mammals (Heide-Jorgensen, 1988, Pedro et al. 2017).

Killer whales occupy both coastal and offshore waters throughout the North Atlantic and within European waters (Bloch and Lockyer 1988, Similä et al. 1996, Samarra et al. 2017, Vogel et al. 2021).

Within European waters there is a history of Killer Whale harvest by whalers and by efforts to cull the species to protect fisheries interests or to supply aquaria (Sigurjónsson and Leatherwood, 1988, Vongraven and Bisther, 1995). Today, killer whales are only actively hunted off East Greenland and takes dramatically increased in this area between 2009 and 2017, with a minimum of 47 whales landed at Tasillaq (Lennert and Richard, 2017).

Persistent organic pollutants (POPs) (e.g. polychlorinated biphenyl (PCBs)), pose a significant risk to killer whales. The species has some of the highest pollutant loads recorded for any animal on the planet (Jepson et al. 2016, Desforges et al. 2018). High contaminant levels have been linked to low reproductive success, compromised immune system, endocrine disruption, and carcinogenicity (Jepson et al. 2016, Dietz et al. 2019). Higher POP burden has been linked to location (proximity to industrial coastlines or sources of contaminants) and to diet (Killer Whales feeding at higher trophic levels accumulate more contaminants due to the effects of biomagnification). It has been suggested that certain subpopulations may be at higher risk of extinction, based on population projection modelling under different POP burdens (Desforges et al. 2018), however, the conclusions of the study have been contested (Witting 2019). Killer Whales in European waters have very high contamination levels, well above the threshold for reproductive impacts (Jepson et al. 2016). The highest levels have been recorded in Killer Whales off the UK and Ireland, the Canary Island and Gibraltar, as well as Greenland. Killer Whale abundance off the UK and Ireland and off Gibraltar is very low, with no-to-very low recruitment (Beck et al. 2014).

Climate change in the Artic is constantly opening new sea areas that were previously covered in ice and therefore not available to Killer Whales (Ferguson et al. 2010). However, unpredictable freezing and lack of experience of Killer Whales in these new areas may lead to ice entrapment of pods, which has been documented in some areas (Westdal et al. 2017, Jourdain et al. 2021). Further, impact of climate change on prey population may also impact killer whales (Jourdain et al. 2019).

Killer Whales also interact with fisheries throughout their range and are known to depredate on long line fisheries and follow trawlers (Similä 2005, Esteban et al. 2016b, Samarra et al. 2018, Mul et al. 2020).

Killer Whales rely on sound for navigation and foraging (echolocation and passive listening) and anthropogenic noise can cause both temporary and permanent hearing loss (Erbe 2002) and impact Killer Whale activity budgets, diving behaviour, and foraging success (Williams et al. 2006, Holt et al. 2009, Lusseau et al. 2009, Kuningas et al. 2013, Samarra and Miller 2016).

Killer Whales are hunted for subsistence off Greenland including the European waters of East Greenland with Killer Whales landed at Tasillaq (Lennert and Richard 2017).

Killer Whales were previously hunted in European waters, primarily within Norwegian waters. Between 1938 and 1981 there were a total of 2,435 Killer Whales caught of which 64% were taken in Norwegian waters (Vongraven and Bisther 1995).

Killer Whale is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES) and Appendices I and II of the Convention on Migratory Species (CMS). Subpopulations outside of Europe, including the eastern North Atlantic and the eastern North Pacific subpopulations are included in Appendix II of CMS.