Processes influencing the population dynamics and conservation of African penguins on Dyer Island, South Africa
Abstract
Dyer Island, South Africa, supported the largest African penguin Spheniscus demersus colony in 1979 (22 655 breeding pairs), but population dynamics of the species have not followed the trends of adjacent colonies in years of high fish abundance or shifts in prey distribution. Less than 1 500 pairs were breeding on Dyer Island in 2013. Available knowledge on demographic parameters was collated and ecological processes were quantified. Juvenile and adult survival probabilities estimated for birds ringed on Dyer Island between 2005 and 2011 were 0.247 (SE 0.06) and 0.545 (SE 0.05) respectively. Juveniles had a high probability (0.918; SE 0.077) of moving away from Dyer Island. Predation by seals and kelp gulls, as well as oiling, are currently important top-down pressures on penguins on Dyer Island. Numbers of birds breeding on the island were negatively correlated with purse-seine catches 20 nautical miles around it. However, it seems that once the colony size is <3 500 breeding pairs, the importance of fishing pressure diminishes, suggesting that once a colony has been reduced to a relatively small size, its growth is limited by pressures other than fishing. From the review of available knowledge presented here, we recommend a number of management options that should be tested in a suitable model.
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The trade-off between top-down and bottom-up selection pressures that drive wild colony size in Sphenisciformes is absent in captive populations.
“However, the trade-off between top-down and bottom-up selection pressures that drive wild colony size in Sphenisciformes (Ludynia et al., 2014) is absent in captive populations.”
From Husbandry and enclosure influences on penguin behavior and conservation breeding (2016) · cites this paper as Ludynia et al., 2014
Conditions for breeding penguins at Dyer Island in recent years were apparently poor.
“and apparently poor conditions for breeding penguins at Dyer Island in recent years [12], [51]”
From Hand-Rearing, Release and Survival of African Penguin Chicks Abandoned Before Independence by Moulting Parents (2014) · cites this paper as [51]
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- Authors
- Ludynia, K., Waller, L., Sherley, R., Abadi, F., Galada, Y., Geldenhuys, D., Crawford, R., Shannon, L., & Jarre, A.
- Affiliations
- University of Cape Town (ZA)
- Scientific Services (ZA)
- Marine Research Institute, Department of Biological Sciences, University of Cape Town, Rondebosch, South Africa
- Corresponding author
- Ludynia, K
- Venue
- African Journal of Marine Science
- Published
- 2014-04-03
- Volume
- 36
- Issue
- 2
- Pages
- 253-267
- ISSN
- 1814-232X (ISSN-L)
- 1814-2338
- OpenAlex
- W2005668638
- Cited by
- 17
- References
- 75
- Citations by year
- 2026: 2 · 2025: 2 · 2024: 2 · 2022: 2 · 2021: 1 · 2017: 1 · 2016: 3 · 2015: 2 · 2014: 2
- FWCI
- 2.32
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- African Journal of Marine Science (publishedVersion)
- Funders
- Claude Leon Foundation
- Topics
- Physical Sciences › Environmental Science › Ecology › Avian ecology and behavior
- Physical Sciences › Environmental Science › Ecology › Marine animal studies overview
- Physical Sciences › Environmental Science › Global and Planetary Change › Marine and fisheries research
- Keywords
- African penguin, Spheniscus demersus, population dynamics, colony decline, survival probability, natal dispersal, seal predation, oiling, fishing pressure, purse seine catch, seabird conservation
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