Browsing by Subject "Spheniscus demersus"

Now showing 1 - 10 of 10
  • Thumbnail Image
    Item
    Open Access
    African penguins Spheniscus demersus recolonise a formerly abandoned nesting locality in Namibia
    (2003) Roux, J-P; Kemper, J; Bartlett, P A; Dyer, B M; Dundee, B L
    African Penguins Spheniscus demersus disappeared from Neglectus Islet probably between 1885 and 1952. Visiting birds were only noted rarely before the mid 1990s, but since 1995 penguin numbers on the islet have increased and breeding was first confirmed in 2001. Neglectus Islet is the only formerly abandoned nesting locality to be recolonised by African Penguins in Namibia. Although the population is still very small (estimated at around 11 breeding pairs), the re-establishment of this breeding locality is important for the conservation of the African Penguin, which is considered to be Critically Endangered in Namibia.
  • Thumbnail Image
    Item
    Restricted
    Aspects of modelling Robben Island African Penguin Spheniscus demersus populations
    (2006) Plagányi, Éva E; Butterworth, Doug S
    Crawford et al. (2006) present relationships between the breeding success of Robben Island African penguins Spheniscus demersus and the abundances of both anchovy Engraulis encrasicolus and sardine Sardinops sagax. Based on their analysis, they suggest that the management of the purse-seine fishery should ensure adequate escapement of fish to maintain the combined biomass of anchovy and sardine above two million tons. Given that this potentially has important repercussions for the management of the pelagic fishery, their analyses have highlighted the importance of further and more detailed investigations into this issue. This paper provides a brief summary of some further considerations in this regard.
  • Thumbnail Image
    Item
    Restricted
    Breeding success of African penguins Spheniscus demersus at Dassen Island, especially after oiling following the Apollo Sea spill
    (2008) Wolfaardt, A C; Underhill, L G; Nel, D C; Williams, A J; Visagie, J
    The reproductive success of African penguins Spheniscus demersus at Dassen Island from 1994 to 2000 was variable, but much higher than previously reported figures for the species. Breeding success was positively related to the abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax, and the high reproductive output during the study was attributed to the large biomass and high availability of these two species for much of the study period. De-oiled penguins from the Apollo Sea spill had a slightly lower hatching success but a significantly lower overall breeding success than that of un-oiled birds, driven mainly by the reduced number of chicks which fledged. Nests with two de-oiled Apollo Sea parents were less successful than nests with one de-oiled bird. There was increased mortality of chicks 40 days and older in nests with de-oiled birds. Chicks from nests with one de-oiled Apollo Sea parent grew at a similar rate to chicks from nests with no de-oiled parents. However, chicks from nests that comprised two de-oiled Apollo Sea birds had significantly slower growth rates than these other two groups. Breeding success and chick growth at nests with de-oiled birds were more negatively impacted when feeding conditions were less favourable. These results suggest that one of the main reasons for lower breeding success in de-oiled birds was their reduced ability to provision chicks, especially during the period in which the energy demands of the chicks is greatest. The rate of mate fidelity was lower in de-oiled birds than un-oiled birds, and there was a positive association between mate fidelity and breeding success.
  • Thumbnail Image
    Item
    Open Access
    Can we determine when marine endotherms feed? A case study with seabirds
    (1992) WILSON, R; Cooper, J; Plötz, Joachim
    The International Society for Burns Injuries (ISBI) has published guidelines for the management of multiple or mass burns casualties, and recommends that 'each country has or should have a disaster planning system that addresses its own particular needs.' The need for a national burns disaster plan integrated with national and provincial disaster planning was discussed at the South African Burns Society Congress in 2009, but there was no real involvement in the disaster planning prior to the 2010 World Cup; the country would have been poorly prepared had there been a burns disaster during the event. This article identifies some of the lessons learnt and strategies derived from major burns disasters and burns disaster planning from other regions. Members of the South African Burns Society are undertaking an audit of burns care in South Africa to investigate the feasibility of a national burns disaster plan. This audit (which is still under way) also aims to identify weaknesses of burns care in South Africa and implement improvements where necessary.
  • Thumbnail Image
    Item
    Restricted
    Data inputs for the African Penguin Spheniscus demersus model to be coupled to the pelagic OMP
    (2008) Plagányi, Éva E; Robinson, William
    This document serves as an updated compilation of all data currently available as inputs to the African penguin spatial model which is to be coupled to the pelagic OMP. The data are presented here together with some comments as to how they are to be used in the model and notes on their derivation and potential reliability. The model presented thus far is spatial in that different populations of penguins are represented, and different levels of movement between these populations are modelled. The main focus of the model is on Dassen and Robben Islands, which were originally combined for reasons of simplicity and because of their close proximity to each other, suggesting that the effects of external factors such as food availability would be highly correlated between the two. However, data that have recently become available indicate differences between these two colonies which suggest that it may no longer be appropriate to pool the two; hence they are split in the model. The third population is Dyer Island because it has the next largest numbers of penguins, recent declines in the population there are of concern and it is considered an important breeding site for penguins given the eastward shift of sardines. The fourth population is Boulders. Although relatively small, this colony was considered important to include because of its position, its role as the focus of several other studies and because penguins are known to have moved from Dyer Island to Boulders, Robben and Dassen, and hence it is useful to quantify to what extent movement of birds away from Dyer Island could account for observed declines at Dyer and increases at these other colonies. A summary of all the breeding colonies of penguins in so-called area i) is provided in Fig. 1 which also shows the relative abundance of breeding pairs in the different sub-areas, computed from data in Underhill et al. (2006). The regional penguin population is dominated (in terms of numbers) by two large colonies, namely Robben Island and Dassen Island; thus the model here has focused on these two colonies, with the next most important colony being Dyer Island. Fig. 2 maps the extent of strata corresponding to pelagic fish biomass estimates used to link to penguin breeding success in the model. Initially relationships were investigated with the west of Cape Agulhas pelagic spawner biomass and the west of Cape Infanta recruit abundances rather than the total South African pelagic fish abundance. More recently, this has been refined further still to use the Cape Columbine to Cape Point spawner biomass component only since this more accurately depicts the biomass available to penguins in the west coast model area. The west of Cape Infanta recruit estimates are retained because the anchovy and sardine recruits move down the West Coast. The model time step is one year and hence average trends are modelled. Penguins in each subarea are modelled starting from 1986.
  • Thumbnail Image
    Item
    Open Access
    Immunological survey of babesiosis ( Babesia peircei ) and toxoplasmosis in Jackass penguins in South Africa
    (1996) Graczyk, TK; Brossy, JJ; Sanders, ML; Dubey, JP; Plös, A; Stoskopf, MK
    Babesia peircei a été extrait d'érythrocytes nucléés provenant de Sphenicus demersus originaires d'Afrique du Sud infectés naturellement. Des fractions de Babesia peircei enrichies en glycoprotéines ont été obtenues par chromatographie sur colonne d'affinité concanavaline A-Sepharose et séparées par électrophorèse en gel de polyacrylamide-dodecylsulfate de sodium (SDS.PAGE). Quatorze bandes protéiques au minimum ont été observées (9, 11, 13, 20, 22, 23, 24, 43, 62, 90, 120, 204, et 205 kDa), la protéine majeure étant de 25 kDa. Des prélèvements sanguins provenant de 191 S. demersus adultes ont été testés par ELISA en utilisant les fractions de B. peircei enrichies en glycoprotéines pour détecter les IgG dirigées contre B. peircei. les prélèvements provenaient de trois groupes de manchots sauvages (n = 110), d'un groupe de manchots (n = 66) ayant été secourus après avoir été contaminés par une marée noire en mer et soignés à la Fondation Nationale Sud Africaine pour la Conservation des Oiseaux littoraux (SANCCOB), et d'un dernier groupe issu des manchots pensionnaires du SANCCOB (n = 15). La prévalence globale pour B. peircei était de 65 %, et la séropositivité moyenne s'échelonnait de 60 à 71 % parmi les cinq groupes de manchots. L'ELISA apparaissait spécifique pour les IgG dirigées contre B. peircei lorsque testée pour les IgG contre Haemoproteus columbae et les IgG contre le paludisme aviaire (Plasmodium relictum, et P. elongatum(, Les anticorps (Ac) dirigés contre Toxoplasma gondii ont été détectés par le test d'agglutination directe utilisant des tachyzoites de T. gondii tués. Tous les oiseaux étaient séronégatifs pour les Ac dirigés contre T. gondii. L'absence de manchots positifs pour T. gondii était due aux conditions sanitaires appropriées et aux méthodes de prévention contre T. gondii utilisées par le SANCCOB.
  • Thumbnail Image
    Item
    Open Access
    Impact of flipper-banding on breeding success of African penguins Spheniscus demersus at Robben Island: comparisons among silicone rubber bands, stainless-steel bands and no bands
    (2008) Barham, P J; Underhill, L G; Crawford, R J M; Leshoro, T M; Bolton, D A
    From 2001 to 2006, two new designs of flipper bands made from silicone rubbers were tested on African penguins Spheniscus demersus at 365 nests on Robben Island, South Africa. We compared, over six years, the breeding success, from hatching to fledging, of three different groups of penguins: those with rubber bands (117 nests), with conventional stainless-steel bands (103 nests) and without bands (145 nests). There were no significant differences in breeding success between the three groups, suggesting that neither the currently used steel bands, nor either of the new rubber-band designs, were harmful during the seasons investigated. The rubber bands caused less wear of feathers and less drag on a model penguin than the steel bands. In captivity, the behaviours of African penguins fitted with rubber bands were not noticeably different to those of unbanded birds.
  • Thumbnail Image
    Item
    Open Access
    Restoration of oiled African penguins Spheniscus demersus a decade after the Apollo Sea spill
    (2008) Wolfaardt, A C; Underhill, L G; Altwegg, R; Visagie, J
    The bulk ore carrier Apollo Sea sank south-west of Dassen Island off western South Africa in June 1994, oiling approximately 10 000 African penguins Spheniscus demersus, most of which were collected from Dassen Island. A total of 4 076 de-oiled penguins was released with flipper bands. From 1994 to 2005, follow-up research using re-sighting and capture-mark-recapture methods indicated that about 73% of the de-oiled penguins observed back at Dassen Island attempted to breed, and were thus successfully restored into the breeding population. For de-oiled breeders, the median interval between their first recorded sighting and first recorded breeding attempt was 11 months, indicating a short-term delay in restoration. At least 45% of the de-oiled breeders were still being re-sighted five years after their release, and a minimum of 4% survived into their ninth year. These results represent the most successful restoration estimates anywhere in the world. The proportion of de-oiled juvenile penguins re-sighted back at Dassen Island and recorded breeding was lower than that of birds in adult plumage. De-oiled non-breeders spent significantly more time along the shore and less time within breeding colonies than de-oiled breeders. The mean proportion of de-oiled breeders that abstained from breeding each year during the study period was greater than expected. There was a negative relationship between breeding and subsequent survival and breeding, suggesting a cost of reproduction for de-oiled birds.
  • Thumbnail Image
    Item
    Open Access
    Revised spatial Age-Structured model of African penguin Spheniscus demersus populations
    (2007) Plagányi, Éva E; Butterworth, Doug S
    A revised form of an earlier model is summarised in this document, with preliminary results to be presented in a separate document. The three main changes to the model are as follows: 1) the delay difference equations have been converted to fully age-structured equations instead so as to be able to model changes in the age at first maturity as requested by the task group; 2) rather than using aggregated factors to model various processes, these factors have been split into individual components so as to be more easily distinguished between and understandable; and 3) a preliminary Algoa Bay model has been added so that movement from Algoa Bay to the west can be modelled. Some suggested alternatives for modelling various processes within the model are given as a starting point for discussions by the task group.
  • Thumbnail Image
    Item
    Restricted
    Surviving off junk: low-energy prey dominates the diet of African penguins Spheniscus demersus at Mercury Island Namibia between 1996 and 2009
    (2010) Ludynia, Katrin; Roux, J-P; Jones, R; Kemper, J; Underhill, Leslie
    The diet of African penguins Spheniscus demersus in Namibia consisted mainly of sardine Sardinops sagax in the 1950s. Since the collapse of pelagic fish stocks in the 1970s, birds fed mainly on bearded (pelagic) goby Sufflogobius bibarbatus, a low-energy prey species. We present diet data for African penguins breeding at Mercury Island, the largest colony for this species in Namibia, between 1996 and 2009. Bearded goby was the main prey item throughout the study period, both in terms of frequency of occurrence (67.8%; SD 31.2) and in terms of mass (59.2%; SD 31.5). Diet composition varied throughout the year as well as between years; birds occasionally fed on a variety of fish species other than bearded goby. In Namibia, poor prey abundance is considered as a major factor contributing to the decline of penguin numbers after the collapse of the sardine stocks. However, bearded goby appears to be relatively abundant along Namibia's southern coast and low prey quality rather than low abundance appears to be a key factor influencing population dynamics of African penguins and other marine top predators in southern Namibia.