Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal

Detalhes bibliográficos
Autor(a) principal: Araújo, Sara Miguel de Matos e
Data de Publicação: 2023
Tipo de documento: Dissertação
Idioma: eng
Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Texto Completo: http://hdl.handle.net/10773/40963
Resumo: It is essential to know how common dolphins (Delphinus delphis) use their habitats so that conservation priorities can be defined, and the impacts of, for instance, anthropogenic activities can be mitigated. Study the behaviour of common dolphins can contribute not only to the protection of the population and ecosystem, but also to achieve several international and national goals regarding sustainable development. The common dolphin is one of the most widely distributed dolphin species and one of the most common cetaceans in Portuguese waters. The south coast of Portugal is a nursery and calving ground for common dolphins, but little is known about their behaviour patterns in this area. Therefore, this work aims to enhance the current knowledge on the habitat use of common dolphins by mapping and modelling their behaviour in the Algarve. The dataset used for the mapping consisted of sightings of common dolphins in the Algarve collected by AIMM – Marine Environment Research Association onboard a dedicated research boat between 2015 and 2020 following random trajectories. To model the occurrence of different behavioural states (i.e., travelling, socialising, foraging, and resting) in relation to the presence/absence of calves and several environmental variables (sea surface temperature, sea surface height above the geoid, bathymetry/distance to coast, slope, and substrate type), multinomial logistic regression models were created. The four behaviours analysed showed a similar overall distribution pattern, with some hotspots in offshore regions of the study area. Travelling was the most common behavioural state, while resting was rarely sighted. The selected model retains temperature and bathymetric slope as significant variables to describe dolphins’ behaviour. The modelling results suggest that as the temperature rises, resting behaviour is more likely to be observed compared to travelling. Furthermore, as slope increases, socialising behaviour is less likely to be observed compared to travelling. These results suggest that, in the current climate change scenario, the increase of water temperature in the study area could lead to an increase in the frequency of resting behaviour of common dolphins inhabiting the area, which could increase the vulnerability of the animals to predators and compromise other essential behaviours, such as foraging. However, more studies are needed to confirm this potential effect. Results also show that this species prefer flatter areas for socialising, which coincide with areas closer to the coast and that offer greater protection against predators. However, more coastal waters are also areas where human activities tend to concentrate. The disruption of social activities by anthropogenic stressors can lead to consequences on the population-level. Therefore, it is important for conservation measures to consider these areas, as they are used for essential behaviours. The implementation of scientific based conservation measures is urgent, considering that in the study area, the results show regular violations of the whale-watching norms by tour boats. Therefore, future studies should also consider, for instance, the effects of vessels on the behaviour of common dolphins in this area.
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spelling Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of PortugalBehaviourCommon dolphinConservationEnvironemntal variablesMappingMultinomial logistic regressionIt is essential to know how common dolphins (Delphinus delphis) use their habitats so that conservation priorities can be defined, and the impacts of, for instance, anthropogenic activities can be mitigated. Study the behaviour of common dolphins can contribute not only to the protection of the population and ecosystem, but also to achieve several international and national goals regarding sustainable development. The common dolphin is one of the most widely distributed dolphin species and one of the most common cetaceans in Portuguese waters. The south coast of Portugal is a nursery and calving ground for common dolphins, but little is known about their behaviour patterns in this area. Therefore, this work aims to enhance the current knowledge on the habitat use of common dolphins by mapping and modelling their behaviour in the Algarve. The dataset used for the mapping consisted of sightings of common dolphins in the Algarve collected by AIMM – Marine Environment Research Association onboard a dedicated research boat between 2015 and 2020 following random trajectories. To model the occurrence of different behavioural states (i.e., travelling, socialising, foraging, and resting) in relation to the presence/absence of calves and several environmental variables (sea surface temperature, sea surface height above the geoid, bathymetry/distance to coast, slope, and substrate type), multinomial logistic regression models were created. The four behaviours analysed showed a similar overall distribution pattern, with some hotspots in offshore regions of the study area. Travelling was the most common behavioural state, while resting was rarely sighted. The selected model retains temperature and bathymetric slope as significant variables to describe dolphins’ behaviour. The modelling results suggest that as the temperature rises, resting behaviour is more likely to be observed compared to travelling. Furthermore, as slope increases, socialising behaviour is less likely to be observed compared to travelling. These results suggest that, in the current climate change scenario, the increase of water temperature in the study area could lead to an increase in the frequency of resting behaviour of common dolphins inhabiting the area, which could increase the vulnerability of the animals to predators and compromise other essential behaviours, such as foraging. However, more studies are needed to confirm this potential effect. Results also show that this species prefer flatter areas for socialising, which coincide with areas closer to the coast and that offer greater protection against predators. However, more coastal waters are also areas where human activities tend to concentrate. The disruption of social activities by anthropogenic stressors can lead to consequences on the population-level. Therefore, it is important for conservation measures to consider these areas, as they are used for essential behaviours. The implementation of scientific based conservation measures is urgent, considering that in the study area, the results show regular violations of the whale-watching norms by tour boats. Therefore, future studies should also consider, for instance, the effects of vessels on the behaviour of common dolphins in this area.Saber como os golfinhos-comum (Delphinus delphis) usam o seu habitat é essencial para definir prioridades de conservação e limitar impactos de atividades potencialmente perturbadoras. Estudar o comportamento do golfinho-comum contribui, não só para a proteção da população e do ecossistema, mas também para alcançar vários objetivos nacionais e internacionais para o desenvolvimento sustentável. O golfinho-comum é uma das espécies de golfinho com uma distribuição mais ampla e é um dos cetáceos mais comuns em águas portuguesas. A costa sul de Portugal é uma área de berçário para esta espécie, mas pouco se sabe sobre o seu comportamento nesta zona. Tendo em conta esta lacuna, este trabalho teve o objetivo de mapear o comportamento do golfinho-comum no Algarve, assim como modelar o seu comportamento em relação a fatores ambientais. O mapeamento foi realizado usando registos de avistamentos de golfinhos-comum no Algarve, recolhidos de 2015 a 2020 pela AIMM – Associação para a Investigação do Meio Marinho, em saídas de barco dedicadas à recolha de dados de megafauna usando trajetórias aleatórias. Para modelar a ocorrência de diferentes estados de comportamento (i.e., deslocação, socialização, alimentação e descanso) em relação ao efeito da presença/ausência de crias e de várias variáveis ambientais (temperatura superficial da água, altura da superfície da água acima do geoide, batimetria/distância à costa e tipo de substrato) foram desenvolvidos modelos de regressão logística multinomial. Os quatro comportamentos analisados mostraram padrões de distribuição semelhantes, com alguns locais de concentração em zonas mais afastadas da costa. O deslocamento foi o comportamento mais comum, enquanto o descanso foi o menos avistado. O modelo selecionado como mais adequado reteve como variáveis significativas para descrever o comportamento a temperatura e o declive do fundo marinho. Os resultados do modelo sugerem que, à medida que a temperatura aumenta, o comportamento de descanso é mais provável de ser observado em comparação com o de deslocação. Mostram também que à medida que o declive aumenta, o comportamento de socialização é menos provável de ser observado em comparação ao de deslocação. Estes resultados parecem sugerir que, no atual contexto das alterações climáticas, o efeito do aumento da temperatura da água na área de estudo poderá levar a um aumento da frequência de momentos de descanso dos golfinhos comuns que habitam a região, facto que poderá aumentar a vulnerabilidade dos animais à predação e comprometer outras atividades essenciais, como a alimentação. No entanto, são necessários mais estudos para confirmar este potencial efeito. Os resultados indicam também que esta espécie socializa preferencialmente em áreas mais planas, coincidentes com áreas mais junto à costa e que apresentam, por isso, maior proteção contra predadores. No entanto, zonas mais costeiras são também zonas onde as atividades antropogénicas se tendem a concentrar. A disrupção da socialização pode ter consequências ao nível populacional e é, por isso, importante que medidas de conservação sejam informadas e considerem o uso destas áreas para estes comportamentos essenciais. Medidas de conservação informadas tornam-se cada vez mais imperativas, considerando que na área de estudo, os resultados evidenciam violações regulares das normas de observação de cetáceos pelas embarcações de observação. Assim, trabalhos futuros devem considerar, por exemplo, efeitos das embarcações no comportamento dos golfinhos-comum.2025-12-22T00:00:00Z2023-12-19T00:00:00Z2023-12-19info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisapplication/pdfhttp://hdl.handle.net/10773/40963engAraújo, Sara Miguel de Matos einfo:eu-repo/semantics/embargoedAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-03-11T01:47:04Zoai:ria.ua.pt:10773/40963Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-20T03:19:59.414389Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
title Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
spellingShingle Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
Araújo, Sara Miguel de Matos e
Behaviour
Common dolphin
Conservation
Environemntal variables
Mapping
Multinomial logistic regression
title_short Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
title_full Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
title_fullStr Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
title_full_unstemmed Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
title_sort Mapping common dolphin (Delphinus delphis) behaviour in the southern coast of Portugal
author Araújo, Sara Miguel de Matos e
author_facet Araújo, Sara Miguel de Matos e
author_role author
dc.contributor.author.fl_str_mv Araújo, Sara Miguel de Matos e
dc.subject.por.fl_str_mv Behaviour
Common dolphin
Conservation
Environemntal variables
Mapping
Multinomial logistic regression
topic Behaviour
Common dolphin
Conservation
Environemntal variables
Mapping
Multinomial logistic regression
description It is essential to know how common dolphins (Delphinus delphis) use their habitats so that conservation priorities can be defined, and the impacts of, for instance, anthropogenic activities can be mitigated. Study the behaviour of common dolphins can contribute not only to the protection of the population and ecosystem, but also to achieve several international and national goals regarding sustainable development. The common dolphin is one of the most widely distributed dolphin species and one of the most common cetaceans in Portuguese waters. The south coast of Portugal is a nursery and calving ground for common dolphins, but little is known about their behaviour patterns in this area. Therefore, this work aims to enhance the current knowledge on the habitat use of common dolphins by mapping and modelling their behaviour in the Algarve. The dataset used for the mapping consisted of sightings of common dolphins in the Algarve collected by AIMM – Marine Environment Research Association onboard a dedicated research boat between 2015 and 2020 following random trajectories. To model the occurrence of different behavioural states (i.e., travelling, socialising, foraging, and resting) in relation to the presence/absence of calves and several environmental variables (sea surface temperature, sea surface height above the geoid, bathymetry/distance to coast, slope, and substrate type), multinomial logistic regression models were created. The four behaviours analysed showed a similar overall distribution pattern, with some hotspots in offshore regions of the study area. Travelling was the most common behavioural state, while resting was rarely sighted. The selected model retains temperature and bathymetric slope as significant variables to describe dolphins’ behaviour. The modelling results suggest that as the temperature rises, resting behaviour is more likely to be observed compared to travelling. Furthermore, as slope increases, socialising behaviour is less likely to be observed compared to travelling. These results suggest that, in the current climate change scenario, the increase of water temperature in the study area could lead to an increase in the frequency of resting behaviour of common dolphins inhabiting the area, which could increase the vulnerability of the animals to predators and compromise other essential behaviours, such as foraging. However, more studies are needed to confirm this potential effect. Results also show that this species prefer flatter areas for socialising, which coincide with areas closer to the coast and that offer greater protection against predators. However, more coastal waters are also areas where human activities tend to concentrate. The disruption of social activities by anthropogenic stressors can lead to consequences on the population-level. Therefore, it is important for conservation measures to consider these areas, as they are used for essential behaviours. The implementation of scientific based conservation measures is urgent, considering that in the study area, the results show regular violations of the whale-watching norms by tour boats. Therefore, future studies should also consider, for instance, the effects of vessels on the behaviour of common dolphins in this area.
publishDate 2023
dc.date.none.fl_str_mv 2023-12-19T00:00:00Z
2023-12-19
2025-12-22T00:00:00Z
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