Red List of South African Species

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Data Deficient (DD)
Assessors: Stephanie Plön Claire Relton
Contributors: Simon Elwen Ken Findlay Michael Meÿer Herman Oosthuizen Matthew Child
Reviewers: Stephanie Plön Claire Relton

Rationale

Kogia breviceps and K. sima are naturally uncommon and there are no regional estimates of population size or trends. However, as they are deep-diving species (up to 800 m), the effects of marine noise pollution should be monitored (although thus far no strandings have been linked to this threat), and we urge more research into the severity of this threat within South African waters. Additionally, plastic pollution should be recognised as an increasing emerging threat, as both species are known to fatally ingest plastic bags mistaken for squid. While their offshore distributions do not overlap with many major threats in the assessment region, their natural scarcity and presumed low population numbers (especially K. breviceps) make them vulnerable to minor threats, which may be increasing in severity in the assessment region. Thus, in line with the global assessments, we list both species as Data Deficient and urge more systematic monitoring and analysis to determine population sizes and trends within the assessment region.

Regional population effects: Pygmy and Dwarf Sperm Whales occur extensively across pelagic waters of tropical and temperate regions, and although their movement patterns are largely unknown, no barriers to dispersal have been recognised, thus rescue effects are considered possible.

Distribution

Both Pygmy Sperm Whales and Dwarf Sperm Whales are widely distributed and inhabit deep tropical, subtropical and temperate waters throughout all oceans (McAlpine 2002). However, the Pygmy Sperm Whale seems to occur more commonly in cooler temperate regions in comparison to the Dwarf Pygmy Whale, which seemingly prefers warmer waters (Caldwell & Caldwell 1989). The distributional ranges of Kogia spp. are poorly known, and most records originate from strandings or occasionally as individuals captured in small fisheries, rather than live sightings at sea (Nagorsen 1985; Caldwell & Caldwell 1989; McAlpine 2002). This may, however, be attributed to their cryptic nature and affiliation for pelagic regions, rather than low population abundances. The Pygmy Sperm Whale is thought to predominantly reside in pelagic regions, beyond the continental shelf edge (Ross 1979). Ballance & Pitman (1998) recorded a number of sightings of Dwarf Pygmy Whales in extremely deep waters (over 3,000 m) in the western Indian equatorial zone.

Within the assessment region, stranding records of Pygmy Sperm Whales suggest that this species occurs from 22°S on South Africa’s west coast to 29°50’S on the east coast (Findlay et al. 1992). Prior to 1977, Ross (1979) documented strandings of 42 Dwarf Sperm Whales along South Africa’s coastline from Saldanha Bay to East London. These and additional records suggest that this species is restricted to South Africa’s southern coast between 17.8°E and 28°E (Ross 1979; Findlay et al. 1992), and an outlying record from KwaZulu-Natal is thought to be attributed to unusual environmental conditions (Ross et al. 1985). The lack of records northwards from Saldanha Bay and along the east coast of South Africa suggests that Dwarf Sperm Whales may prefer the mixed-water conditions, where the Benguela and Agulhas Currents mix (Ross 1984). There appears to be no seasonal variation in the occurrence of either Dwarf or Pygmy Sperm Whales within the assessment region (Skinner & Chimimba 2005), and their movement patterns are largely unknown.

Population trend

Trend

Abundance estimates of these species are often underestimates due to their offshore habitats, long and deep-diving behaviour and inconspicuous nature at the surface (Barlow 1999). For example, Dwarf Sperm Whales lie very low in the water when on the surface and can only be seen when wind speeds are between 0 and 2 on the Beaufort scale. Additionally, Pygmy and Dwarf Sperm Whales are often confused during sightings, which further complicates any population assessments. Although no global population estimates are available for either species, the stranding frequency of K. breviceps in regions such as South Africa and the southeastern United States suggests they may be more common than sightings records would imply (Taylor et al. 2008a). Similarly, although no regional population estimates exist for K. breviceps in the southern hemisphere, there appears to be substantial gene flow between stocks (S. Plön pers. comm.). These species are primarily known from stranding records, which are declining across the region. However, because the cause of strandings are largely unknown, it is unclear how this trend is reflective of the population. There have been no recent sighting records of either species within the South African exclusive economic zone (EEZ).

The 3-generation period of the species is calculated as 36 years (Taylor et al. 2007), and, globally, a 30% reduction over three generations cannot be ruled out (Taylor et al. 2008a, 2008b).

Threats

Although no major threats have been recognised for Kogia spp. within the assessment region, and the threats listed below are not likely to cause drastic population reduction on their own, they may result in slow, significant declines in the future, especially if the threats synergise.

Kogia spp. were not historically hunted commercially, but are currently hunted on a small-scale in regions such as Japan, Taiwan, Sri Lanka, Indonesia and the Lesser Antilles (Jefferson et al. 1993), and there are reports of sporadic accidental bycatch of Pygmy Sperm Whales in gillnet, longline and purse seine fisheries across the northern hemisphere (Jefferson et al. 1993; Barlow et al. 1997; Perez et al. 2001; Garrison 2007). Similarly, Dwarf Sperm Whales are also occasionally caught as bycatch in many areas of its range (including southern Brazil; Zerbini & Kotas 1998). No direct or indirect catches of these species have been reported from South African waters, and Baird et al. (1996) suggests that direct and indirect catches of the Pygmy Sperm Whale are not expected to severely impact their population stability.

The ingestion of plastic bags (which the animals possibly mistake for squid) is common among squid-eating cetaceans, and has been documented for K. breviceps (for example, Scott et al. 2001; Stamper et al. 2006), and is considered to be relatively common among these species. Plastic pollution in the stomachs of cetaceans frequently hinders natural digestion of food resources, leading to gut-blockage, starvation, strandings and death (Caldwell & Caldwell 1989; Laist et al. 1999; S. Plön pers. obs.). There is no direct evidence for K. sima being affected by either plastic ingestion or noise pollution. However, since they have a large niche overlap (S. Plön unpubl. data) with K. breviceps, they are likely to be as affected as K. breviceps.

As deep-diving species (similar to beaked whales), Dwarf and Pygmy Sperm Whales are presumably vulnerable to anthropogenic noise pollution, for example those produced by seismic surveys and sonar generated during naval operations (Cox et al. 2006; Wang & Yang 2006; Yang et al. 2008). A number of recent stranding events, which included Kogia spp. have been documented in Taiwan (Wang & Yang 2006; Yang et al. 2008), the Gulf of Mexico and off the east coast of Florida (Waring et al. 2006). Although, anthropogenic noise pollution is a possible cause of these stranding incidents, due to spatial and temporal associations, this assumption has not been confirmed (Hohn et al. 2006; Wang & Yang 2006; Yang et al. 2008). Marine noise pollution is thought to be intensifying within South African waters (Koper & Plön 2012).

The impact of global climate change, and the associated effects of increased water temperature and CO2 concentration on Kogia spp. is largely unknown, however, is likely to have cascading effects on the movements and feeding ecology of these species (Learmonth et al. 2006).

Uses and trade

Although these species are hunted at low levels in some parts of their range, there is no trade or use of these species within the assessment region. In other parts of the world, such as the Philippines, Kogia spp. are hunted for bait to be used in fisheries or meat for human consumption (Leatherwood et al. 1992; Anonymous 1996). Additionally, where they are caught accidentally in fisheries, such as gillnets, they may also be utilised for human consumption (Klinowska 1991; Muñoz-Hincapié et al. 1998).

Conservation

Both K. breviceps and K. sima are listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In the absence of further data, no specific conservation measures can be recommended for these species within the assessment region at present. Continued research is necessary into the impact of and interactions between threats, such as plastic and noise pollution, climate change and incidental bycatches in pelagic fisheries. Management plans should be developed as such data become available.

Recommendations for managers and practitioners:
  • The interaction between Kogia spp. and gillnet, purse seine and longline fisheries requires ongoing monitoring, and regular records of bycatch should be collected by fishing operations.
Research priorities:
  • Population size, distribution and trends of these species in South African waters.
  • Investigations into threats to these species, such as the impacts and severity of marine pollution (both plastics and noise) on populations.
Encouraged citizen actions:
  • Use information dispensed by the South African Sustainable Seafood Initiative to make good choices when buying fish in shops and restaurants, e.g. wwfsa.mobi, FishMS 0794998795.
  • Save electricity and fuel to mitigate CO2 emissions and hence, the rate of climate change.
  • Sightings data from pelagic commercial tourism operators may be valuable.
  • Report any strandings to the relevant local authorities.

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