Browsing by Subject "breeding"

Now showing 1 - 3 of 3
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    Bayesian assessments of the southern hemisphere humpback whale breeding stock B using three different models for stock-structure
    (2010) Müller, Andrea; Butterworth, Doug S; Johnston, Susan J
    Three different models are considered for Southern Hemisphere humpback breeding stock B: Model 1, a single fully-mixed stock; Model 2, reproductively independent stocks B1 off Gabon and B2 of the southern African coastline; and Model 3 with two stocks as in Model 2 but with B1 consisting of two sub-stocks, one of which migrates to Gabon along the southern African coastline. The models are fitted to mark-recapture data (both photo-ID and genetic) available for the Gabon and South African regions. The purpose of the paper is one of illustrating the stock-structure models and associated methods of analysis, anticipating that further discussion and selection of specific model input assumptions will take place during the Scientific Committee meeting.
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    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.
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    The Evolutionary Ecology of Sprouting in Woody Plants
    (2003) Bond, William J; Midgley, Jeremy J
    Woody plants may be killed by severe disturbance or resprout from vegetative tissue. Sprouters can persist at a site through several generations of nonsprouters. Differences in sprouting behavior are therefore important for understanding vegetation dynamics, extinction risks, and woody plant management. Although sprouting appears not to be uniquely correlated with many other intrinsic attributes, such as specific leaf area or breeding systems, a clear correlate is reduced seedling aboveground growth rates from sprouters allocating more to belowground structures. Consequently, sprouters tend to have low seedling recruitment rates, and saplings take longer to reach maturity. Sprouters also tend to have lower seed output than nonsprouters, but comparative studies have seldom taken other trait differences such as plant size into account. Added to these trade-offs between persistence and recruitment, sprouters are often multi stemmed and shorter than related nonsprouters and may be outcompeted by them when disturbances are rare. Since sprouters tend to have long generation times, damped demographic trends, and gene flow across generations, it has been suggested that their speciation rates would be low. The available data, primarily from fire-prone Gondwanan shrublands in South Africa, show no strong differences in speciation rates of related sprouters versus seeders. This indicates that ecological factors are important determinants of the evolution of fire life