Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living ... more Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based surveys conducted over a 6-year period in an area of approximately 5,400 km2 (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation within the population of the Azores.
Despite the openness of the oceanic environment, limited dispersal and tight social structure oft... more Despite the openness of the oceanic environment, limited dispersal and tight social structure often induce genetic structuring in marine organisms, even in large animals such as cetaceans. In the bottlenose dolphin, mitochondrial and nuclear DNA analyses have revealed the existence of genetic differentiation between pelagic (or offshore) and coastal (or nearshore) ecotypes in the western North Atlantic, as well as between coastal populations. Because previous studies concentrated on continental margins, we analysed the population structure of bottlenose dolphins in two of the most isolated archipelagos of the North Atlantic: the Azores and Madeira. We analysed 112 samples collected on live animals in the two archipelagos, and nine samples collected on stranded animals in Madeira and mainland Portugal. Genetic analyses consisted in molecular sexing, sequencing of part of the mitochondrial hyper-variable region, and screening of ten microsatellite loci. We predicted that: (1) there is at least one pelagic and one or more coastal populations in each archipelago; (2) populations are differentiated between and possibly within archipelagos. Contrary to these predictions, results indicated a lack of population structure in the study area. In addition, comparison with published sequences revealed that the samples from the Azores and Madeira were not significantly differentiated from samples of the pelagic population of the western North Atlantic. Thus, bottlenose dolphins occurring in the pelagic waters of the North Atlantic belong to a large oceanic population, which should be regarded as a single conservation unit. Unlike what is known for coastal populations, oceanic bottlenose dolphins are able to maintain high levels of gene flow.
Seabirds have the potential to be used as indicators for monitoring changes in the southern ocean... more Seabirds have the potential to be used as indicators for monitoring changes in the southern oceans. However, many species and populations are still poorly known. The thin-billed prion ( Pachyptila belcheri) is the most abundant seabird species around the Falkland Islands, but this far, no detailed censuses of its populations had been carried out. In this study, we developed a methodology, based on standard field methods combined with a Geographical Information System, to census the biggest known colony (New Island) of this species. Data were also collected on nesting habitat preferences. Results indicate that there are 1,081,000 (95% confidence limits: 815,000–1,346,000) apparently active nest-burrow entrances on New Island South which, given the very high occupancy rates by known breeders, should correspond to a similar number of nesting couples. We present quantitative evidence that this result can be extrapolated for the entire island, giving an overall estimate of 2 million pairs. Prions have an almost ubiquitous distribution on New Island, but they are more frequent in areas with steeper slopes (excluding cliffs). Habitats dominated by introduced grass species generally hold higher densities of nests in comparison to most native formations.
... G12 8QQ, UK. c Departamento de Oceanografia e Pescas, Universidade dos Açores, 9901-862 Horta... more ... G12 8QQ, UK. c Departamento de Oceanografia e Pescas, Universidade dos Açores, 9901-862 Horta, Portugal; Luís Monteiro was killed in a tragic accident in the Azores. This paper is dedicated to his memory. d Department ...
Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living ... more Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based surveys conducted over a 6-year period in an area of approximately 5,400 km2 (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation within the population of the Azores.
Despite the openness of the oceanic environment, limited dispersal and tight social structure oft... more Despite the openness of the oceanic environment, limited dispersal and tight social structure often induce genetic structuring in marine organisms, even in large animals such as cetaceans. In the bottlenose dolphin, mitochondrial and nuclear DNA analyses have revealed the existence of genetic differentiation between pelagic (or offshore) and coastal (or nearshore) ecotypes in the western North Atlantic, as well as between coastal populations. Because previous studies concentrated on continental margins, we analysed the population structure of bottlenose dolphins in two of the most isolated archipelagos of the North Atlantic: the Azores and Madeira. We analysed 112 samples collected on live animals in the two archipelagos, and nine samples collected on stranded animals in Madeira and mainland Portugal. Genetic analyses consisted in molecular sexing, sequencing of part of the mitochondrial hyper-variable region, and screening of ten microsatellite loci. We predicted that: (1) there is at least one pelagic and one or more coastal populations in each archipelago; (2) populations are differentiated between and possibly within archipelagos. Contrary to these predictions, results indicated a lack of population structure in the study area. In addition, comparison with published sequences revealed that the samples from the Azores and Madeira were not significantly differentiated from samples of the pelagic population of the western North Atlantic. Thus, bottlenose dolphins occurring in the pelagic waters of the North Atlantic belong to a large oceanic population, which should be regarded as a single conservation unit. Unlike what is known for coastal populations, oceanic bottlenose dolphins are able to maintain high levels of gene flow.
Seabirds have the potential to be used as indicators for monitoring changes in the southern ocean... more Seabirds have the potential to be used as indicators for monitoring changes in the southern oceans. However, many species and populations are still poorly known. The thin-billed prion ( Pachyptila belcheri) is the most abundant seabird species around the Falkland Islands, but this far, no detailed censuses of its populations had been carried out. In this study, we developed a methodology, based on standard field methods combined with a Geographical Information System, to census the biggest known colony (New Island) of this species. Data were also collected on nesting habitat preferences. Results indicate that there are 1,081,000 (95% confidence limits: 815,000–1,346,000) apparently active nest-burrow entrances on New Island South which, given the very high occupancy rates by known breeders, should correspond to a similar number of nesting couples. We present quantitative evidence that this result can be extrapolated for the entire island, giving an overall estimate of 2 million pairs. Prions have an almost ubiquitous distribution on New Island, but they are more frequent in areas with steeper slopes (excluding cliffs). Habitats dominated by introduced grass species generally hold higher densities of nests in comparison to most native formations.
... G12 8QQ, UK. c Departamento de Oceanografia e Pescas, Universidade dos Açores, 9901-862 Horta... more ... G12 8QQ, UK. c Departamento de Oceanografia e Pescas, Universidade dos Açores, 9901-862 Horta, Portugal; Luís Monteiro was killed in a tragic accident in the Azores. This paper is dedicated to his memory. d Department ...
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