Behavioural flexibility in an endangered seabird during current changes
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
Involving fishermen in seabirds’ conservation: bridging the gap between socio-economic needs of industry and the needs of seabirds
- Authors: Ginsburg, Tayla
- Date: 2019
- Subjects: Sea birds -- Ecology , Island ecology Island animals -- Conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42184 , vital:36633
- Description: Marine ecosystems and species face multiple threats, particularly intensive industrial-scale fishing activities. As the human population continues to increase exponentially and drive a greater demand for food, commercial fishing effort will likely intensify. While terrestrial protected areas are well developed, marine protected areas (MPAs) are less so, both in the area covered and management practices. There is currently a drive to increase the extent of MPAs, both globally and in South Africa, particularly for those ecosystems and marine species that can benefit from area-based management. The size, shape, location zonation of MPAs generally remain static through time. However, the ocean is a dynamic environment and static MPAs are not always able to achieve conservation objectives for their component ecosystems and species. Dynamic Ocean Management (DOM) is an approach that integrates near real-time data on biological, oceanographic, social and/or economic variables to adjust an MPAs boundary and zonation in both space and time. The aim of this thesis was to assess the viability of applying DOM to a fishing exclusion zone within a zoned MPA in Algoa Bay, South Africa, to support conservation objectives for the Endangered African penguin Spheniscus demersus. Algoa Bay supports half of the world’s remaining population of this species. First, the degree of spatial overlap between foraging penguins and purse-seine fishers in Algoa Bay was determined over five years. In all years, purse-seiner fishing vessels were located around or near to St Croix Island and a large proportion of the total pelagic fish catch from the Bay was removed from this area. Breeding penguins travelled significantly further while foraging when the overlap (and subsequent competition for pelagic fish) was higher, suggesting that African penguins would benefit from a fishing exclusion zone around St Croix Island owing to reduced competition. However, an exclusion zone can have socio-economic impacts on fisheries as a result of the lost fishing area. A common concern raised by fishers is the direct loss of income, either as a result of increased fuel costs to reach alternate fishing grounds or decreased catch. An analysis of catch and travel time (as a proxy for fuel costs) when a 20 km exclusion zone was present or absent around St Croix Island revealed that the exclusion zone scenarios had no significant impact on either variable. Interviews with individuals in the local purse-seine fishery (both fishers and factory managers) showed a consensus that the marine environment needs protection and that MPAs have various environmental benefits. Despite this, individuals were concerned about how they would be impacted by the exclusion zone in the MPA. The interviews highlighted the willingness of individuals in the purse-seine fishery to talk to and work with scientists.
- Full Text:
- Date Issued: 2019
- Authors: Ginsburg, Tayla
- Date: 2019
- Subjects: Sea birds -- Ecology , Island ecology Island animals -- Conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42184 , vital:36633
- Description: Marine ecosystems and species face multiple threats, particularly intensive industrial-scale fishing activities. As the human population continues to increase exponentially and drive a greater demand for food, commercial fishing effort will likely intensify. While terrestrial protected areas are well developed, marine protected areas (MPAs) are less so, both in the area covered and management practices. There is currently a drive to increase the extent of MPAs, both globally and in South Africa, particularly for those ecosystems and marine species that can benefit from area-based management. The size, shape, location zonation of MPAs generally remain static through time. However, the ocean is a dynamic environment and static MPAs are not always able to achieve conservation objectives for their component ecosystems and species. Dynamic Ocean Management (DOM) is an approach that integrates near real-time data on biological, oceanographic, social and/or economic variables to adjust an MPAs boundary and zonation in both space and time. The aim of this thesis was to assess the viability of applying DOM to a fishing exclusion zone within a zoned MPA in Algoa Bay, South Africa, to support conservation objectives for the Endangered African penguin Spheniscus demersus. Algoa Bay supports half of the world’s remaining population of this species. First, the degree of spatial overlap between foraging penguins and purse-seine fishers in Algoa Bay was determined over five years. In all years, purse-seiner fishing vessels were located around or near to St Croix Island and a large proportion of the total pelagic fish catch from the Bay was removed from this area. Breeding penguins travelled significantly further while foraging when the overlap (and subsequent competition for pelagic fish) was higher, suggesting that African penguins would benefit from a fishing exclusion zone around St Croix Island owing to reduced competition. However, an exclusion zone can have socio-economic impacts on fisheries as a result of the lost fishing area. A common concern raised by fishers is the direct loss of income, either as a result of increased fuel costs to reach alternate fishing grounds or decreased catch. An analysis of catch and travel time (as a proxy for fuel costs) when a 20 km exclusion zone was present or absent around St Croix Island revealed that the exclusion zone scenarios had no significant impact on either variable. Interviews with individuals in the local purse-seine fishery (both fishers and factory managers) showed a consensus that the marine environment needs protection and that MPAs have various environmental benefits. Despite this, individuals were concerned about how they would be impacted by the exclusion zone in the MPA. The interviews highlighted the willingness of individuals in the purse-seine fishery to talk to and work with scientists.
- Full Text:
- Date Issued: 2019
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