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Kogia Spp. – Pygmy and Dwarf Sperm Whales

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Kogia Spp. – Pygmy and Dwarf Sperm Whales Kogia spp. – Pygmy and Dwarf Sperm Whales Taxonomic notes: Before 1966, only one species of Kogia was described, K. breviceps (the Pygmy Sperm Whale), however succeeding studies (Handley 1966; Chivers et al. 2005) documented the distinctions between this species, and the Dwarf Sperm Whale (K. sima). Additionally, recent morphological and mitochondrial DNA evidence found unexpectedly that there may be two monophyletic groups of K. sima, an Indo-Pacific group and an Atlantic group (Chivers et al. 2005). As suggested by Chivers et al. (2005), until supporting evidence confirms the status of two genetically isolated species within the K. sima taxon, we recognise this as one species. Previously, K. simus was used to describe the Dwarf Sperm Whale, however Kogia breviceps this was considered grammatically incorrect, and was later altered to K. sima (Rice 1998). Currently, no subspecies of K. breviceps have been identified (Skinner & Chimimba Regional Red List status (2016) 2005). Kogia breviceps Data Deficient*† Kogia sima Data Deficient*† Assessment Rationale National Red List status (2004) Kogia breviceps and K. sima are naturally uncommon and there are no regional estimates of population size or K. breviceps Least Concern trends. However, as they are deep-diving species (up to K. sima Least Concern 800 m), the effects of marine noise pollution should be monitored (although thus far no strandings have been Reasons for change Non-genuine change linked to this threat), and we urge more research into the Global Red List status severity of this threat within South African waters. Additionally, plastic pollution should be recognised as an K. breviceps (2012) Data Deficient increasing emerging threat, as both species are known to K. sima (2012) Data Deficient fatally ingest plastic bags mistaken for squid. While their offshore distributions do not overlap with many major TOPS listing (NEMBA) (2007) None threats in the assessment region, their natural scarcity and CITES listing (2003) Appendix II presumed low population numbers (especially K. breviceps) make them vulnerable to minor threats, Endemic No which may be increasing in severity in the assessment *Watch-list Data †Watch-list Threat region. Thus, in line with the global assessments, we list both species as Data Deficient and urge more systematic Kogia spp. have been documented basking on monitoring and analysis to determine population sizes and the surface of the ocean (Yamada 1954), and trends within the assessment region. although they can often be easily approached, if distressed they excrete extensive clouds of dark Regional population effects: Pygmy and Dwarf Sperm reddish-brown faeces, in order to conceal Whales occur extensively across pelagic waters of tropical themselves from the perceived threat and temperate regions, and although their movement (Caldwell & Caldwell 1989). patterns are largely unknown, no barriers to dispersal have been recognised, thus rescue effects are considered possible. Taxonomy Distribution Kogia breviceps (Blainville 1838) Both Pygmy Sperm Whales and Dwarf Sperm Whales are widely distributed and inhabit deep tropical, subtropical Kogia sima (Owen 1866) and temperate waters throughout all oceans (McAlpine ANIMALIA - CHORDATA - MAMMALIA - 2002). However, the Pygmy Sperm Whale seems to occur CETARTIODACTYLA - PHYSETERIDAE - Kogia more commonly in cooler temperate regions in comparison to the Dwarf Pygmy Whale, which seemingly Common names: Kogia breviceps: Pygmy Sperm Whale, prefers warmer waters (Caldwell & Caldwell 1989). The Lesser Cachalot, Lesser Sperm Whale (English), distributional ranges of Kogia spp. are poorly known, and Dwergpotvis (Afrikaans). Kogia sima: Dwarf Sperm Whale, most records originate from strandings or occasionally as Owen’s Pygmy Sperm Whale (English), Miniatuurpotvis individuals captured in small fisheries, rather than live (Afrikaans) sightings at sea (Nagorsen 1985; Caldwell & Caldwell Taxonomic status: Species 1989; McAlpine 2002). This may, however, be attributed to Recommended citation: Plön S, Relton C. 2016. A conservation assessment of Kogia spp. In Child MF, Roxburgh L, Do Linh San E, Raimondo D, Davies-Mostert HT, editors. The Red List of Mammals of South Africa, Swaziland and Lesotho. South African National Biodiversity Institute and Endangered Wildlife Trust, South Africa. The Red List of Mammals of South Africa, Lesotho and Swaziland Kogia spp. | 1 Figure 1. Distribution range for Pygmy Sperm Whale (Kogia breviceps) within the assessment region (IUCN 2012a) their cryptic nature and affiliation for pelagic regions, surface (Barlow 1999). For example, Dwarf Sperm Whales rather than low population abundances. The Pygmy lie very low in the water when on the surface and can only Sperm Whale is thought to predominantly reside in be seen when wind speeds are between 0 and 2 on the pelagic regions, beyond the continental shelf edge (Ross Beaufort scale. Additionally, Pygmy and Dwarf Sperm 1979). Ballance & Pitman (1998) recorded a number of Whales are often confused during sightings, which further sightings of Dwarf Pygmy Whales in extremely deep complicates any population assessments. Although no waters (over 3,000 m) in the western Indian equatorial global population estimates are available for either zone. species, the stranding frequency of K. breviceps in regions such as South Africa and the southeastern United Within the assessment region, stranding records of Pygmy States suggests they may be more common than Sperm Whales suggest that this species occurs from 22°S sightings records would imply (Taylor et al. 2008a). on South Africa’s west coast to 29°50’S on the east coast Similarly, although no regional population estimates exist (Findlay et al. 1992). Prior to 1977, Ross (1979) for K. breviceps in the southern hemisphere, there documented strandings of 42 Dwarf Sperm Whales along appears to be substantial gene flow between stocks (S. South Africa’s coastline from Saldanha Bay to East Plön pers. comm.). These species are primarily known London. These and additional records suggest that this from stranding records, which are declining across the species is restricted to South Africa’s southern coast region. However, because the cause of strandings are between 17.8°E and 28°E (Ross 1979; Findlay et al. 1992), largely unknown, it is unclear how this trend is reflective of and an outlying record from KwaZulu-Natal is thought to the population. There have been no recent sighting be attributed to unusual environmental conditions (Ross et records of either species within the South African al. 1985). The lack of records northwards from Saldanha exclusive economic zone (EEZ). Bay and along the east coast of South Africa suggests that Dwarf Sperm Whales may prefer the mixed-water The 3-generation period of the species is calculated as 36 conditions, where the Benguela and Agulhas Currents mix years (Taylor et al. 2007), and, globally, a 30% reduction (Ross 1984). There appears to be no seasonal variation in over three generations cannot be ruled out (Taylor et al. the occurrence of either Dwarf or Pygmy Sperm Whales 2008a, 2008b). within the assessment region (Skinner & Chimimba 2005), Current population trend: Unknown and their movement patterns are largely unknown. Continuing decline in mature individuals: Unknown Population Number of mature individuals in population: Unknown Abundance estimates of these species are often Number of mature individuals in largest subpopulation: underestimates due to their offshore habitats, long and Unknown deep-diving behaviour and inconspicuous nature at the Kogia spp. | 2 The Red List of Mammals of South Africa, Lesotho and Swaziland Figure 2. Distribution range for Dwarf Sperm Whale (Kogia sima) within the assessment region (IUCN 2012b) Number of subpopulations: Unknown 900 m (S. Plön pers. obs.). Similarly, the stomach contents of Dwarf Pygmy Whales insinuate that this Severely fragmented: No species routinely dives to about 600 m to feed, possibly even deeper, and is mostly found over the continental Habitats and Ecology shelf (Ross 1979; S. Plön pers. obs.). The majority of the diet of Kogia spp. consists of cephalopods, but they may Pygmy Sperm Whales inhabit deep waters over the also consume other prey, for example deep-sea fishes continental shelf and slope (Ross 1979; S. Plön pers. and shrimps (McAlpine et al. 1997; dos Santos & comm.). Although some studies document some division Haimovici 2001; S. Plön pers. comm.). Ross (1979) between K. breviceps and K. sima in their preference for documented that in South African waters, Pygmy and water depth, Mullin et al. (1994) using aerial observations Dwarf Sperm Whales consumed at least 67 and 38 noted that in the Gulf of Mexico, both species occurred in different prey species, respectively, and Pygmy Sperm waters between 400–600 m deep. These depths Whales are likely to feed in deeper waters compared to constituted the upper regions of the continental slope, Dwarf Sperm Whales. which exhibited high concentrations of zooplankton (Baumgartner et al. 2001). Both species appear to feed Although little is known about the reproductive biology of over the deeper continental shelf and slope (Ross 1979; S. Kogia spp., and no seasonality can be inferred, female Plön pers. obs.). and male K. breviceps from South Africa are estimated to reach sexual maturity at 2.7–2.8 m and 2.7–3.0 m, Ross (1979) reported that Pygmy Sperm Whales may respectively, while both sexes of K. sima reach sexual occur individually or in small groups of up
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