Composition and Possible Function of Social Groupings of Southern Right Whales in South African Waters

Southern right whales (Eubalaena australis) are distributed throughout the Southern Hemisphere, where they seasonally migrate betweenhigh latitude feeding grounds and low latitude breeding grounds. While there are detailed records of historical and recent whaling off thesouthern, southwestern and southeastern African coasts, historical catches in Madagascar’s waters are poorly documented. There have alsobeen no recent, documented sightings of southern right whales off the east coast of Madagascar. Here we report two sightings, one of asingle individual in Antongil Bay in northeastern Madagascar and the other of a mother and calf pair near Fort Dauphin on the southeasterncoast. DNA obtained from a biopsy sample of the single animal showed it was a male possessing one of the common South Atlantic rightwhale mitochondrial haplotypes. The available DNA data provide limited suggestive evidence that the individuals documented offMadagascar represent long-distance migrants from the well-documented South African population. However, the possibility that thesesouthern right whales are members of a small or remnant population from the historical whaling grounds of Delagoa Bay, Sofala Bay orthe Crozet Island feeding grounds cannot be excluded. Regardless of population assignment for these individuals, it appears that somesouthern right whales may be using different parts of Madagascar’s east coast during the wintering season

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Mortalities of right whales and related anthropogenic factors in South African waters, 1963-1998

J. Cetacean Res. Manage. ◽

10.47536/jcrm.vi.293 ◽

2020 ◽

pp. 171-176

Author(s):

Peter B. Best ◽

Victor M. Peddemors ◽

Victor G. Cockcroft ◽

Nan Rice

Keyword(s):

Population Growth ◽

South African ◽

Causes Of Death ◽

Anthropogenic Factors ◽

Population Recovery ◽

Right Whale ◽

Right Whales ◽

Southern Right Whales

Between 1963 and 1998, 55 mortalities of southern right whales and a further three ‘possible right whale’ mortalities were recorded on theSouth African coastline. Of the known right whale mortalities, 31 could be classified as ‘calves of the year’, 8 as juveniles and 14 as adults.Relatively few (6.5-16.1%) of the calf mortalities could be attributed to anthropogenic factors, compared to juveniles (25-50%) and adults(35.7-57.1%). Apparent causes of death included ship strikes (4 definite, 7 possible) and entanglement (4 definite, 1 possible), with oneharpooning incident. Five non-fatal ship strikes and 16 instances of non-fatal entanglement were also recorded. Whilst the gear mostcommonly involved in non-fatal entanglement was crayfish trap lines, three of the four entanglement fatalities involved longline gear. Theincidence of scars attributable to previous entanglement remained constant amongst mature females from 1979-1997, at 3-4%. Recordedmortalities increased over the period 1963-1997 at a rate no different from that of population growth over the same period. The current levelof anthropogenic mortality does not seem to be affecting population recovery.

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