Red List of South African Species

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Least Concern (LC)
Assessors: Ryan Reisinger Nico de Bruyn Marthan Bester Ken Findlay
Contributors: Claire Relton Shanan Atkins Simon Elwen Mike Meyer Herman Oosthuizen Stephanie Plön
Reviewers: Matthew Child

Rationale

This taxonomic unit is treated as one species in this assessment even though it may be more complicated. At least two subpopulations of Killer Whales have been recognised within South African waters, those occurring off mainland South Africa, and those associated with the region around the Prince Edward Islands. While a monitoring programme recently initiated at the Prince Edward Islands presently provides some data for that subpopulation and will provide more complete information (especially demographic parameters) in future, the South African subpopulation is almost entirely unknown. No abundance estimates are available for the entire assessment region, but there are considered to be 20–50 mature individuals occurring around the Prince Edward Islands. Population size, structure and movement of Killer Whales should be determined.

No major threats that could cause rapid decline were identified and there is no reason to believe there are rangewide declines. However, the minor threat of competition with the longline fisheries, which may cause occasional, intentional deaths, was identified in both subpopulations. Interactions with longline fisheries should continue to be monitored and ideally a photographic identification catalogue should be established to determine which individuals are depredating.

The species is wide-ranging and common and its habitat is not fragmented. Such connectivity, combined with the lack of major identified threats, means we list this species as Least Concern. If taxonomy is resolved, re-assessment at subspecies or subpopulation level may be required.

Regional population effects: The Killer Whale is an extremely wide-ranging pelagic cetacean, with a continuous distribution and no obvious barriers to dispersal, thus rescue effects are possible.

Distribution

The Killer Whale is a well-known cosmopolitan species, and with the exception of humans, may be the most widespread mammal across the globe (Heyning &  Dahlheim 1988; Rice 1998). In general, this species occurs most commonly within high productivity and temperate nearshore regions (Forney & Wade 2006), however they are not restricted by water temperature or depth.

The species ranges across the entire assessment region from Kosi Bay to the Orange River mouth, and around the Prince Edward Islands, across all water depths (Best 2007). Sightings from the Durban whaling grounds suggest peak occurrence in June and October, and Elephant Seal (Mirounga leonina) remains in the stomach contents of some individuals captured there indicate movement from sub-Antarctic waters (Findlay 1989; Findlay et al. 1992; Best et al. 2010), which is also suggested by satellite tracking (Reisinger et al. 2015). Together these may indicate seasonal or transient occurrence of at least some individuals.

Population trend

Trend

Killer Whales at the Prince Edward Islands bear some morphological resemblance to Antarctic Type B Killer Whales (and are genetically closely related; Moura et al. 2015), whilst those found in mainland waters have until recently been assumed to be Type A (Best 2007). However, strong evidence should be provided before populations are defined as or assigned to ecotypes (de Bruyn et al. 2013). Among Killer Whales stranded on the South African coast, small individuals with significant tooth wear have been designated as a new flat-toothed morphotype (Best et al. 2014); this is potentially supported by the large haplotype diversity among South African Killer Whales (Moura et al. 2014).

There are no population estimates for mainland South Africa and there are very few sighting and stranding data available (but see Findlay et al. 1992; Best et al. 2010). However, an ongoing photo-identification study at the Prince Edward Islands has identified around 57 individuals, of which 37 were mature (Reisinger et al. 2011b; Reisinger & de Bruyn 2014).

The Prince Edward Islands population and a group of individuals that prey on common dolphins (Delphinus spp.) in False Bay may be considered cultural groups, where culture refers to “information or behaviour – shared by a population or subpopulation – which is acquired from conspecifics through some form of social learning” (Rendell & Whitehead 2001). In this case the specific hunting strategies used by these socially connected groups at particular locations could be considered culture. As such, they may qualify as conservation value subpopulations.

There is potentially some exchange and almost certainly some spatial overlap between the two subpopulations. Four of the 36 Killer Whales landed by whalers off Durban  had Southern Elephant Seal remains in their stomachs (Best et al. 2010) and the Prince Edward Islands (PEIs) are the nearest Southern Elephant Seal breeding colony. Among Killer Whales satellite-tracked from the PEIs, one individual travelled northwards to ~34.9°S; 37.3°E (Reisinger et al. 2015). This position is near to, but does not actually overlap, the distribution of South African sightings reported by Best et al. (2010). However, this is more likely to represent a lack of sighting (or reporting) effort offshore of South Africa. Moreover, Killer Whales are capable of travelling long distances. Yet there have been no photographic matches between the PEIs and South Africa, and Killer Whales from South Africa and the PEIs are morphologically distinct (Best 2007; Best et al. 2010); although the differences may not be apparent to untrained/inexperience observers or in poor sighting conditions at sea. The PEIs population is composed mainly of animals which show strong seasonal residence at the PEIs (Keith et al. 2001; Reisinger et al. 2011a; R. Reisinger & N. de Bruyn unpubl. data). All the PEIs animals sampled share a single haplotype (they are closely related) (Janse van Rensburg et al. 2013), and northward movements from the PEIs of satellite tracked individuals have been rapid, with individuals subsequently returning to the PEIs (Reisinger et al. 2015). This leads to the inference that the subpopulations are distinct, but may overlap spatially at times.

Although these subpopulation sizes are small and thus would qualify for a threatened listing, this species is wideranging and its distribution is not fragmented. There is no expected continuing decline in the number of subpopulations or mature individuals. Thus, there is no reason to suspect this species is threatened within South African waters.

Model based estimates of generation time are 25.7 years (Taylor et al. 2007). The most detailed information on demographic parameters are from a long term (1970) study of populations of Resident Killer Whales in the northeast Pacific (Olesiuk et al. 1990, 2005). Some key parameters from this population (1996–2004):
  • Mean age at first birth: 15.4 years
  • Mean calving interval: 5.5 years
  • Estimated reproductive potential: 4.5 calves
  • Realized calf production: 2.2 calves
  • Mean life expectancy (females): 30 years
  • Mean life expectancy (males): 19 years
  • Longevity (females): ~ 80 years
  • Estimated maximum longevity (males): ~ 40–50 years
  • Mean annual mortality: 3.4%
  • Cumulative juvenile mortality (up to recruitment age, 15.5 years): 39.2%
  • Population composition: juveniles ~ 47%; reproductive females ~ 24%; post-reproductive females ~ 11%; adult males ~ 18%. Based on a photographic identification study at the Prince Edward Islands (Tosh et al. 2008; Reisinger et al. 2011b; Reisinger & de Bruyn 2014), population composition for the period 2006–2013 is summarised in Table 1.

Threats

No major threats to this species have been identified; however, unofficial communications indicate that deepwater longliners use dynamite to scare off Killer Whales that remove catches from the longlines. Killer Whale mortalities are expected, but numbers are unknown. Killer Whales steal hooked fish from deep-water longline fishing vessels in South African waters and around the PEIs (Tilney & Purves 1999; Kock et al. 2006; Williams et al. 2009). From 1999-2001 Killer Whales interacted with 33– 64% of longlining cruises to the PEIs (Kock et al. 2006). In South African waters from 2002–2006, Killer Whales depredated 0.5% of total catch on monitored vessels (Williams et al. 2009). Fishermen (illegally) attempt to deter these Killer Whales using explosives or firearms (Kock et al. 2006); this may obviously result in injury or death, but has not been quantified. Poncelet et al. (2010) suggested that lethal interactions with longline fisheries may be one of the causes for the declining population size and survivorship of the Crozet Killer Whale population (1964-2002). Tixier et al. (2010) report relatively constant depredation rates around the Crozet Islands, but the social transmission and spread of this behaviour among  Killer Whales is likely (e.g. Fearnbach et al. 2014).

Killer Whales depredate Patagonian Toothfish from seven longline fishing vessels around the Crozet Islands, ~1,000 km east of Marion. Tixier (2012) estimated that Killer Whales depredated 116 t / year of Patagonian Toothfish between 2001 and 2010. Pot fishing and acoustic harassment devices (AHDs) have been used in an attempt to mitigate this interaction. Catch per unit effort during pot fishing was not economically sustainable (Gasco et al. 2010) and Killer Whales appear to become habituated to AHDs after the first exposure, which also raises concerns about the effect of the loud amplitude noise on Killer Whales' hearing (Tixier et al. 2014b).

Tixier et al. (2014a) showed that several variables influenced the interaction between Killer Whales and fishing vessels: short longline sets (< 5 km) and faster hauling speeds decreased losses; the depth of longline sets, the distance travelled between sets and the number of vessels operating simultaneously all decreased the probability of interaction (Tixier et al. 2014a). Tixier et al. (2010) recommended that vessels move > 40 nautical miles before fishing again and, after an interaction, lines < 5 km be used. However local factors may influence how effective such mitigation measures are (Tixier et al. 2014a).

Persistent bio-accumulating contaminants are inferred to pose a potential threat to Killer Whales that inhabit, or prey on high trophic level prey that occupy coastal zones (Cockcroft 1999), such as the individuals which prey on common dolphins in False Bay. Contaminants such as persistent organic pollutants (POPs) are ubiquitous in marine environments and since they accumulate at higher trophic levels (biomagnification), Killer Whales are particularly at risk (e.g. Ross et al. 2000). Noël et al. (2009) found relatively high concentrations of POPs in Killer Whales at the Crozet Islands, 1,000 km east of Marion Island. Although polychlorinated biphenyl (PCB) concentrations were lower than in Northern Hemisphere populations, in 70% of individuals they were still above a conservative 1.3 mg / kg marine mammal health threshold (Mos et al. 2007), demonstrating that marine mammals from even remote locations are at risk.

Uses and trade

There is no contemporary trade or use of this species in South Africa.

Conservation

This species is fully protected in South African waters through national legislation – Marine Living Resources Act, 1998 (Act No. 18 of 1998) and the Prince Edward Islands Act, 1948 (Act No. 43 of 1948). The species is listed in Appendix II of CITES. Mitigation of Killer Whale interaction with longline fishing vessels is considered the only major conservation intervention necessary for this species at present. Thus, continued research into the spatiotemporal patterns of longline-Killer Whale interactions is necessary, and observer protocols should be standardised to ensure the collection of valuable, unbiased data (Kock et al. 2006). 

Studies on taxonomy, subpopulation structure, abundance and life history are needed for the South African and Prince Edward Island areas. Regional subpopulations of Killer Whales can be small and highly specialized, and therefore vulnerable to over-exploitation and habitat deterioration. Several small subpopulations elsewhere in the world have already been recognized as having a high risk of extinction (e.g. Southern Resident Killer Whales; Krahn et al. 2004). Within potential subpopulations, cultural uniqueness which has high conservation value should be identified and conserved.

Photographic identification at the Prince Edward Islands is the only systematic monitoring programme for this species (e.g. Reisinger et al. 2011b; Reisinger & de Bruyn 2014). Similar, although unsystematic, photo-identification has been carried out on the False Bay common dolphin predating group over the last five years. 

Recommendations for managers and practitioners:
  • Interactions between Killer Whales and longline fisheries require monitoring.
  • Investigations into the development of effective depredation mitigation measures are urgently required.
  • Assessment of the severity of factors that are expected to pose potential threats by virtue of distribution patterns of Killer Whales should be made.
Research priorities:
  • Taxonomic resolution of South African and Prince Edward Island Killer Whale stocks to determine population identity and any subsequent subspecies distribution.
  • Current population size and trend estimates are urgently required.
  • Foraging range and diet, including potential response of prey resources to the effects of climate change.
  • Within potential subpopulations, cultural uniqueness which has high conservation value should be identified and conserved.
  • Movement and foraging range studies are required to assess overlap, if any, of identified groups.
Current ongoing research projects:
  • Prince Edwards Islands – Marion Island Marine Mammal Programme, Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria: The Mammal Research Institute has opportunistically monitored Killer Whales at the Prince Edward Islands since the 1970s (see Condy et al. 1978), but recently (2006) dedicated Killer Whale work has been launched. The project is based on photographic identification of individuals and includes aspects such as satellite tracking, genetics and stable isotope analyses (www.marionseals.com).
  • South Africa – no dedicated projects, although some opportunistic work on the False Bay animals has been conducted and additional work has been proposed.
Encouraged citizen actions:
  • Foraging ecology research at Marion Island is progressing but impeded by the financial investment that is required for satellite telemetry. Aid in funding this aspect can be securely provided through: http:// www.givengain.com/cause/4655/.
  • Use information dispensed by the South African Sustainable Seafood Initiative (SASSI) to make good choices when buying fish in shops and restaurants, e.g. wwfsa.mobi, FishMS 0794998795.
  • Buy fresh produce that has been grown in pesticidefree environments.
  • Save electricity and fuel to mitigate CO2 emissions and hence, the rate of climate change.
  • Buy local products that have not been shipped.
  • Reduce boat speed in bays and harbours.
  • Report sightings on MammalMAP. Sightings of Killer Whales and photographs suitable for photographic identification can be uploaded to MammalMAP or reported to the Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria.
  • When participating in whale/dolphin watching tours, ensure regulations are adhered to.
  • Don’t approach or chase Killer Whales in boats.
  

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 author = {Olesiuk PF, Ellis GM, Ford JKB},
 institution = {Canadian Science Advisory Secretariat, Fisheries and Oceans Canada},
 title = {Life history and population dynamics of northern resident killer whales (<i>Orcinus orca</i>) in British Columbia},
 year = {2005}
}
,@inbook{15421,
 address = {San Diego, California, USA},
 author = {},
 booktitle = {Species},
 editor = {Perrin, W.F.},
 pages = {1084--1087},
 publisher = {Academic Press},
 title = {Encyclopedia of Marine Mammals. Second edition},
 year = {2009}
}
,@article{15421,
 author = {Pitman RL, Durban JW},
 journal = {Polar Biology},
 pages = {1589--1594},
 title = {Killer whale predation on penguins in Antarctica},
 volume = {33},
 year = {2010}
}
,@article{15421,
 author = {Poncelet É, Barbraud C, Guinet C},
 journal = {Journal of Cetacean Research and Management},
 pages = {41--48},
 title = {Population dynamics of killer whales (<i>Orcinus orca</i>) in the Crozet Archipelago, southern Indian Ocean: a mark–recapture study from 1977 to 2002},
 volume = {11},
 year = {2010}
}
,@article{15421,
 author = {Rabearisoa N, Bach P, Tixier P, Guinet C},
 journal = {Journal of Experimental Marine Biology and Ecology},
 pages = {55--63},
 title = {Pelagic longline fishing trials to shape a mitigation device of the depredation by toothed whales},
 volume = {432},
 year = {2012}
}
,@article{15421,
 author = {Reisinger RR, de Bruyn PJN, Tosh CA, Oosthuizen WC, Mufanadzo NT, Bester MN},
 journal = {African Journal of Marine Science},
 pages = {99--105},
 title = {Prey and seasonal abundance of killer whales at sub-Antarctic Marion Island},
 volume = {33},
 year = {2011}
}
,@techreport{15421,
 author = {Reisinger RR, de Bruyn PN},
 institution = {Mammal Research Institute, University of Pretoria 10},
 title = {Marion Island killer whales: 2006–2013},
 year = {2014}
}
,@article{15421,
 author = {Reisinger RR, de Bruyn PN, Bester MN},
 journal = {Aquatic Biology},
 pages = {177--185},
 title = {Abundance estimates of killer whales at subantarctic Marion Island},
 volume = {12},
 year = {2011}
}
,@article{15421,
 author = {Reisinger RR, Keith M, Andrews RD, de Bruyn PJN},
 journal = {Journal of Experimental Marine Biology and Ecology},
 pages = {90--102},
 title = {Movement and diving of killer whales (<i>Orcinus orca</i>) at a Southern Ocean archipelago},
 volume = {473},
 year = {2015}
}
,@article{15421,
 author = {Rendell L, Whitehead H},
 journal = {Behavioral and Brain Sciences },
 pages = {360--373},
 title = {Cetacean culture: still afloat after the first naval engagement of the culture wars},
 volume = {24},
 year = {2001}
}
,@techreport{15421,
 address = {Sydney, Australia, 1–5 February 1999, FAO Rome.},
 author = {Tilney R, Purves MG},
 institution = {Proceedings of the international conference on integrated fisheries monitoring},
 title = {The status of integrated fisheries monitoring in South Africa},
 year = {1999}
}
,@phdthesis{15421,
 author = {Tixier P},
 school = {Université d’Aix Marseille II},
 title = {Déprédation par les orques (<i>Orcinus orca</i>) et les cachalots (<i>Physeter macrocephalus</i>) sur les palangriers à la légine australe dans la ZEE de l’archipel de Crozet},
 year = {2012}
}
,@article{15421,
 author = {Tixier P, Garcia JV, Gasco N, Duhamel G, Guinet C},
 journal = {ICES Journal of Marine Science: Journal du Conseil},
 pages = {1--11},
 title = {Mitigating killer whale depredation on demersal longline fisheries by changing fishing practices},
 year = {2014}
}
,@article{15421,
 author = {Tixier P, Gasco N, Duhamel G, Guinet C},
 journal = {ICES Journal of Marine Science: Journal du Conseil},
 pages = {1--9},
 title = {Habituation to an acoustic harassment device (AHD) by killer whales depredating demersal longlines},
 year = {2014}
}
,@article{15421,
 author = {Tixier P, Gasco N, Duhamel G, Guinet C},
 journal = {Marine Mammal Science},
 pages = {983--1003},
 title = {Depredation of Patagonian toothfish (<i>Dissostichus eleginoides</i>) by two sympatrically occurring killer whale (<i>Orcinus orca</i>) ecotypes: Insights on the behavior of the rarely observed type D killer whales},
 volume = {32},
 year = {2016}
}
,@article{15421,
 author = {Tixier P, Gasco N, Duhamel G, Viviant M, Authier M, Guinet C},
 journal = {CCAMLR Science },
 pages = {179--195},
 title = {Interactions of Patagonian toothfish fisheries with killer and sperm whales in the Crozet islands Exclusive Economic Zone: an assessment of depredation levels and insights on possible mitigation strategies},
 volume = {17},
 year = {2010}
}
,@article{15421,
 author = {Tosh CA, de Bruyn PJN, Bester MN},
 journal = {Marine Mammal Science},
 pages = {929--940},
 title = {Preliminary analysis of the social structure of killer whales, <i>Orcinus orca</i>, at subantarctic Marion Island},
 volume = {24},
 year = {2008}
}
,@article{15421,
 author = {Williams AJ, Petersen SL, Goren M, Watkins BP},
 journal = {African Journal of Marine Science},
 pages = {81--86},
 title = {Sightings of killer whales <i>Orcinus orca</i> from longline vessels in South African waters, and consideration of the regional conservation status},
 volume = {31},
 year = {2009}
}
,]
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