P. J. N. de Bruyn

Sex at sea: alternative mating system in an extremely polygynous mammal

Financial support was provided by the South African Department of Science and Technology, through the National Research Foundation, in support of the Marine Mammal Programme of the MRI.

Cephalopod diet of the Cape fur seal, Arctocephalus pusillus pusillus , along the Namibian coast : variation due to location

Scats of the Cape fur seal, Arctocephalus pusillus pusillus, were sampled at four mainland colonies, Cape Cross, Atlas Bay,Wolf Bay and Van Reenen Bay, along the Namibian coast over a period of eight years (1994–2001) to assess the diversity and spatial variability in the cephalopod component of the seal diet. Additional scat samples were collected from the Possession Island seal colony (1999–2000) to gain a broader perspective of spatial variation. A uniform and low diversity of cephalopods, only six species amongst all colonies, was identified, indicating that independently the scat sampling method is unsatisfactory for determining species diversity within the diet. Given the ease of scat collection, this method does, however, provide valuable insight into the variability of the most important species in the diet. Ommastrephids dominated the cephalopod component of the diet of seals from Atlas/Wolf Bay and Cape Cross, both in terms of wet mass and numbers. Sepia australis proved to be numerically the most important cephalopod in the diet of seals from Possession Island and Van Reenen Bay, while Octopus magnificus dominated at these colonies in terms of wet mass. Contrary to previous findings it is suggested that seals from Van Reenen Bay and Possession Island forage south of the upwelling cell at Lüderitz (in the southern Benguela ecosystem), while previous evidence of Atlas/Wolf Bay and Cape Cross seals foraging north of this upwelling cell (in the northern Benguela ecosystem) is supported. Prey specimen size differences, within species between colonies, were identified, but lack of cephalopod life history and movement data, and scat sampling biases preclude adequate explanation of these findings, indicating the necessity for further studies.

First record of a vagrant Commerson's dolphin, Cephalorhynchus commersonii, at the southern African continental shelf

ABSTRACT Commersons Dolphins Cephalorhynchus commersonii are distributed in two disjunct populations, one around southern South America and the other around the sub-Antarctic Kerguelen Islands. These populations have been shown to be morphologically and genetically distinct and movement between the two populations is unlikely. We report on the sighting of a single specimen over the South African continental shelf on 13 November 2004. To our knowledge this is the first record of this species in South African waters and such a vast distance (over 4000 km) from the known distribution limits.

First confirmed record of a leucistic Antarctic fur seal pup born outside the Scotia Arc Islands

A leucistic Antarctic fur seal (Arctocephalus gazella) pup was born on subantarctic Marion Island during the austral summer of 2010/2011. This is the first confirmed record of a leucistic fur seal pup born outside the Scotia Arc islands. Additionally, we report on a leucistic adult female Antarctic fur seal producing typical black pups for five non-consecutive summers on Marion Island. The birth of a leucistic pup, together with the multiple black pups produced by the leucistic female, suggests that the recessive genes responsible for leucism are now entrenched within the Marion Island population.

Inshore Occurrence of Southern Right Whales (Eubalaena australis) at Subantarctic Marion Island

Opportunistic shore-based sightings of southern right whales Eubalaena australis for Marion Island (46°54′S, 37°45′E) were documented at five different times between 1974 and 2009. Whales were sighted between May and September and exclusively on the eastern lee side of the Island. Notwithstanding some observer biases over this time frame, the species appears to be an infrequent visitor to the inshore marine environment of Marion Island.

Who's the boss? Giant petrel arrival times and interspecific interactions at a seal carcass at sub-Antarctic Marion Island

Most northern giant petrels Macronectes halli arrived before southern giant petrels Macronectes giganteus at a seal carcass at sub-Antarctic Marion Island and left earlier. In interspecific interactions, southern giant petrels initiated and dominated encounters. Level of aggression may be related to the degree of satiation. Dominance by southern giant petrels at seal carcasses may help explain why northern giant petrels commence breeding earlier than southern giant petrels in sympatric situations.