Spheniscus demersus

About: Spheniscus demersus is a research topic. Over the lifetime, 309 publications have been published within this topic receiving 6869 citations.

Responses by four seabird species to a fluctuating availability of Cape Anchovy Engraulis capensis off South Africa

Abstract: In recent years, Cape Anchovy Engraulis capensis has been the most important food for four seabirds breeding in South Africa–African Penguin Spheniscus demersus, Cape Gannet Morus capensis, Cape Cormorant Phalacrocorax capensis and Swift Tern Sterna bergii. Between 1984 and 1992, biomass of spawning anchovy fluctuated between about 0.5 and 1.75 million tons. Abundance of anchovy was significantly related to numbers of chicks fledged by African Penguins, occurrence of anchovy in the diet of Cape Gannets and numbers of Cape Cormorants and Swift Terns that attempted to breed. Numbers of African Penguins and Cape Gannets that attempted breeding probably also were influenced by abundance of anchovy. African Penguins and Cape Cormorants abandoned nests when anchovy were scarce and deferred breeding until anchovy became more plentiful. Survival of immature African Penguins in a period of anchovy scarcity was enhanced by availability of South African Sardine Sardinops sagax as an alternative food. When anchovy abundance was low, Cape Gannets fed on sardine.

Collapse of South Africa’s penguins in the early 21st century

Abstract: The number of African penguins Spheniscus demersus breeding in South Africa collapsed from about 56 000 pairs in 2001 to some 21 000 pairs in 2009, a loss of 35 000 pairs (>60%) in eight years. This reduced the global population to 26 000 pairs, when including Namibian breeders, and led to classification of the species as Endangered. In South Africa, penguins breed in two regions, the Western Cape and Algoa Bay (Eastern Cape), their breeding localities in these regions being separated by c. 600 km. Their main food is anchovy Engraulis encrasicolus and sardine Sardinops sagax, which are also the target of purse-seine fisheries. In Algoa Bay, numbers of African penguins halved from 21 000 pairs in 2001 to 10 000 pairs in 2003. In the Western Cape, numbers decreased from a mean of 35 000 pairs in 2001–2005 to 11 000 pairs in 2009. At Dassen Island, the annual survival rate of adult penguins decreased from 0.70 in 2002/2003 to 0.46 in 2006/2007; at Robben Island it decreased from 0.77 to 0.55 in the same peri...

Foraging Behavior of Gentoo and Chinstrap Penguins as Determined by New Radiotelemetry Techniques

Abstract: -Analysis of radio signals from transmitters affixed to 7 Gentoo (Pygoscelis papua) and 6 Chinstrap (P. antarctica) penguins allowed us to track penguins at sea. Signal characteristics allowed us to distinguish among 5 foraging behaviors: porpoising, underwater swimming, horizontal diving, vertical diving, and resting or bathing. Gentoo Penguins spent a significantly greater portion of their foraging trips engaged in feeding behaviors than Chinstraps, which spent significantly more time traveling. Gentoos had significantly longer feeding dives than Chinstraps (128 s vs. 91 s) and significantly higher dive-pause ratios (3.4 vs. 2.6). These differences in foraging behavior suggest Gentoo and Chinstrap penguins may have different diving abilities and may forage at different depths. Received 3 June 1985, accepted 24 April 1986. THE trophic relationships among Pygoscelis penguins, the Adelie (P. adeliae), Chinstrap (P. antarctica), and Gentoo (P. papua), have been a major focal point of research in recent years, particularly with respect to the ecology of their major prey species, krill (Euphausia superba). To date, however, our knowledge of the birds' feeding ecology is largely derived from stomach samples obtained ashore (Emison 1968; Croxall and Furse 1980; Croxall and Prince 1980a; Volkman et al. 1980, 1986; Lishman 1985). Diving depth is one aspect of penguin foraging behavior that has been investigated in some detail. Multiple depth recorders, logging the number of dives within set depth ranges, have been deployed on King (Aptenodytes patagonica; Kooyman et al. 1982), Chinstrap (Lishman and Croxall 1983), and Gentoo (Costa pers. comm.) penguins. Maximum diving depths have been reported for Emperor (A. forsteri; Kooyman et al. 1971), Black-footed (Spheniscus demersus; Wilson and Bain 1984), and Gentoo (Adams and Brown 1983) penguins. Feeding range also has been investigated, but indirectly, using nest relief intervals (Williams and Siegfried 1980, Ainley et al. 1984, Croxall et al. 1984). We report a new method of tracking penguins at sea that allowed us to differentiate 1 Present address: National Marine Mammal Laboratory, NOAA/NMFS, 7600 San Point Way N.E., Seattle, Washington 98115 USA. among behaviors during foraging trips. This method improved our understanding of penguin feeding efficiencies, ranges, and traveling speeds, and permitted preliminary comparisons of Gentoo and Chinstrap penguin forag-