Browsing by Author "Dinis, Ana"
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- Behavioural Ecology Traits of Elusive Deep-Diver Whales Unravel a Complex Social Structure Influenced by Female Philopatry and Defence PolygynyPublication . Badenas, Anja; Dinis, Ana; Ferreira, Rita; Sambolino, Annalisa; Hamard, Eliette; Berninsone, Leonardo G.; Fernandez, Marc; Alves, Filipe M. A.Knowledge of the role of individual associations has provided an insightful understanding of the structures of animal societies, especially in highly social mammals such as primates. Yet, this is unbalanced towards marine mammals, particularly to beaked whales, due to their elusive nature. In addition, information on the fundamental drivers of the social structure of these deep-diving animals is still scarce. Here, the hypothesis of female defence polygyny was tested in Blainville’s beaked whales (Mesoplodon densirostris) and discussed within the context of marine and terrestrial organisms displaying similar patterns, by (i) estimating residency times to obtain information on the movements into and out of the area, (ii) analysing social networks to assess individual association metrics, (iii) measuring the strength of the associations to assess the existence of preferred or avoided relationships among individuals, and (iv) modelling different social structures to address temporal patterns in social relationships. Using a 9-year photographic dataset derived from the pelagic habitat, individual associations were inferred based on likelihood techniques. This approach allowed to infer on the species’ social structure in relation to age class, sex, residency status, and spatio-temporal patterns, which can be a good practice to be applied for other taxa. Heterogeneity in capture probability and residency times was observed between age-sex classes, with adult females exhibiting long-term site fidelity. This suggests different habitat roles and spatial structuring within this social organisation. Strong and long dyadic associations occurred between adult females and immatures, contrarily to between males, and the best-fitting models of the temporal patterns suggested long-lasting and temporary associations. The present findings unravel a complex social structure stratified by age-sex class and influenced by female philopatry and defence polygyny, like an unimale group mating system, which varies from other beaked whales but is similar to some birds, pinnipeds, or non-human primates.
- Climate change vulnerability of cetaceans in Macaronesia : Insights from a trait-based assessmentPublication . Sousa, Andrielly O.; Alves, François; Arranz, Patricia; Dinis, Ana; Fernandez, Marc; González García, L.; Morales, Manuel B.; Lettrich, Matthew D.; Coelho, R. Encarnação; Costa, H.; Lourenço, T. Capela; Azevedo, José M. N.; Santos, C. FrazãoOver the last decades global warming has caused an increase in ocean temperature, acidification and oxygen loss which has led to changes in nutrient cycling and primary production affecting marine species at multiple trophic levels. While knowledge about the impacts of climate change in cetacean's species is still scarce, practitioners and policymakers need information about the species at risk to guide the implementation of conservation measures. To assess cetacean's vulnerability to climate change in the biogeographic region of Macaronesia, we adapted the Marine Mammal Climate Vulnerability Assessment (MMCVA) method and applied it to 21 species management units using an expert elicitation approach. Results showed that over half (62%) of the units assessed presented Very High (5 units) or High (8 units) vulnerability scores. Very High vulnerability scores were found in archipelago associated units of short-finned pilot whales (Globicephala macrorhynchus) and common bottlenose dolphins (Tursiops truncatus), namely in the Canary Islands and Madeira, as well as Risso's dolphins (Grampus griseus) in the Canary Islands. Overall, certainty scores ranged from Very High to Moderate for 67% of units. Over 50% of units showed a high potential for distribution, abundance and phenology changes as a response to climate change. With this study we target current and future information needs of conservation managers in the region, and guide research and monitoring efforts, while contributing to the improvement and validation of trait-based vulnerability approaches under a changing climate.
- Daytime dive characteristics from six short-finned pilot whales Globicephala macrorhynchus off Madeira IslandPublication . Alves, Filipe M. A.; Dinis, Ana; Ribeiro, Cláudia; Nicolau, Cátia; Kaufmann, Manfred; Fortuna, Caterina M.; Freitas, LuísSix time-depth recorders attached with suction-cups were deployed in resident and transient adult short-finned pilot whales to evaluate their daytime diving characteristics in their preferred habitat area off Madeira Island. Here, data on the proportion of time spent at the surface and at different dive phases (descent, bottom and ascent), dive depths and dive rates are presented. With mean attachment durations of 2 h 31 min (SD=2 h), the whales spent a considerable amount of time at the surface (mean=76.3%, SD=18.6) and presented a low diving rate (mean=6.8 dives h‾¹, SD=6.1; considering dive as submergence deeper than 10 m). The maximum dive depth recorded in this study was 988 m, and dives deeper than 500 m, which were recorded from resident and transient whales, suggest foraging activity along their preferred habitat area. The analysis of dives deeper than 100 m shows that the percentage of time spent on descent, bottom or ascent varied between dives, with means of ~40, 30 and 30%, respectively.
- Large-scale movements of common bottlenose dolphins in the Atlantic : dolphins with an international courtyardPublication . Dinis, Ana; Molina, Carlota; Tobeña, Marta; Sambolino, Annalisa; Hartman, Karin L.; Fernandez, Marc; Magalhães, Sara; Santos, Rui Peres dos; Ritter, Fabian; Martín, Vidal; Aguilar de Soto, Natacha; Alves, Filipe M. A.Wide-ranging connectivity patterns of common bottlenose dolphins (Tursiops truncatus) are generally poorly known worldwide and more so within the oceanic archipelagos of Macaronesia in the North East (NE) Atlantic. This study aimed to identify long-range movements between the archipelagos of Macaronesia that lie between 500 and 1,500 km apart, and between Madeira archipelago and the Portuguese continental shelf, through the compilation and comparison of bottlenose dolphin's photo-identification catalogues from different regions: one from Madeira (n = 363 individuals), two from different areas in the Azores (n = 495 and 176), and four from different islands of the Canary Islands (n = 182, 110, 142 and 281), summing up 1791 photographs. An additional comparison was made between the Madeira catalogue and one catalogue from Sagres, on the southwest tip of the Iberian Peninsula (n = 359). Results showed 26 individual matches, mostly between Madeira and the Canary Islands (n = 23), and between Azores and Madeira (n = 3). No matches were found between the Canary Islands and the Azores, nor between Madeira and Sagres. There were no individuals identified in all three archipelagos. The minimum time recorded between sightings in two different archipelagos (≈ 460 km apart) was 62 days. Association patterns revealed that the individuals moving between archipelagos were connected to resident, migrant and transient individuals in Madeira. The higher number of individuals that were re-sighted between Madeira and the Canary Islands can be explained by the relative proximity of these two archipelagos. This study shows the first inter-archipelago movements of bottlenose dolphins in the Macaronesia region, emphasizing the high mobility of this species and supporting the high gene flow described for oceanic dolphins inhabiting the North Atlantic. The dynamics of these long-range movements strongly denotes the need to review marine protected areas established for this species in each archipelago, calling for joint resolutions from three autonomous regions belonging to two EU countries.
- Modeling Fine-Scale Cetaceans’ Distributions in Oceanic Islands : Madeira Archipelago as a Case StudyPublication . Fernandez, Marc; Alves, Filipe M. A.; Ferreira, Rita; Fischer, Jan-Christopher; Thake, Paula; Nunes, Nuno; Caldeira, Rui; Dinis, AnaSpecies distributional estimates are an essential tool to improve and implement effective conservation and management measures. Nevertheless, obtaining accurate distributional estimates remains a challenge in many cases, especially when looking at the marine environment, mainly due to the species mobility and habitat dynamism. Ecosystems surrounding oceanic islands are highly dynamic and constitute a key actor on pelagic habitats, congregating biodiversity in their vicinity. The main objective of this study was to obtain accurate fine-scale spatio-temporal distributional estimates of cetaceans in oceanic islands, such as the Madeira archipelago, using a long-term opportunistically collected dataset. Ecological Niche Models (ENM) were built using cetacean occurrence data collected on-board commercial whale watching activities and environmental data from 2003 to 2018 for 10 species with a diverse range of habitat associations. Models were built using two different datasets of environmental variables with different temporal and spatial resolutions for comparison purposes. State-of-the-art techniques were used to iterate, build and evaluate the MAXENT models constructed. Models built using the long-term opportunistic dataset successfully described distribution patterns throughout the study area for the species considered. Final models were used to produce spatial grids of species average and standard deviation suitability monthly estimates. Results provide the first fine-scale (both in the temporal and spatial dimension) cetacean distributional estimates for the Madeira archipelago and reveal seasonal/annual distributional patterns, thus providing novel insights on species ecology and quantitative data to implement better dynamic management actions.
- A novel expert-driven methodology to develop thermal response curves and project habitat thermal suitability for cetaceans under a changing climatePublication . Sousa, Andreia G.; Fernandez, Marc; Alves, Filipe M. A.; Arranz, Patricia; Dinis, Ana; González García, Laura; Morales, Misael; Lettrich, Matthew D.; Coelho, R. Encarnação; Costa, Hugo; Lourenço, T. Capela; Azevedo, José M. N.; Santos, Catarina FrazãoOver the last decades, global warming has contributed to changes in marine species composition, abundance and distribution, in response to changes in oceanographic conditions such as temperature, acidification, and deoxygenation. Experimentally derived thermal limits, which are known to be related to observed latitudinal ranges, have been used to assess variations in species distribution patterns. However, such experiments cannot be undertaken on free-swimming large marine predators with wide-range distribution, like cetaceans. An alternative approach is to elicit expert's knowledge to derive species' thermal suitability and assess their thermal responses, something that has never been tested in these taxa. We developed and applied a methodology based on expert-derived thermal suitability curves and projected future responses for several species under different climate scenarios. We tested this approach with ten cetacean species currently present in the biogeographic area of Macaronesia (North Atlantic) under Representative Concentration Pathways 2.6, 4.5 and 8.5, until 2050. Overall, increases in annual thermal suitability were found for Balaenoptera edeni, Globicephala macrorhynchus, Mesoplodon densirostris, Physeter macrocephalus, Stenella frontalis, Tursiops truncatus and Ziphius cavirostris. Conversely, our results indicated a decline in thermal suitability for B. physalus, Delphinus delphis, and Grampus griseus. Our study reveals potential responses in cetaceans' thermal suitability, and potentially in other highly mobile and large predators, and it tests this method's applicability, which is a novel application for this purpose and group of species. It aims to be a cost-efficient tool to support conservation managers and practitioners.
- Spatial and temporal distribution of bottlenose dolphins, Tursiops truncatus, in the Madeira archipelago, NE AtlanticPublication . Dinis, Ana; Carvalho, A.; Alves, Filipe M. A.; Nicolau, Cátia; Ribeiro, Cláudia; Kaufmann, Manfred; Cañadas, A.; Freitas, LuísOne of the first steps in understanding the relationships between populations and their habitats is to determine which areas they use with higher frequency. This study used systematic and non-systematic survey data from 2001-2002 and 2004-2012 to determine encounter rates and investigate temporal and spatial distribution of bottlenose dolphins around Madeira, Desertas and Porto Santo islands. A total 24,914 km of search effort was carried out and 199 sightings were recorded. Highest encounter rates were found off the east coast of Madeira and off Porto Santo. Moreover, higher encounter rates occurred over bathymetries ranging between 500-1,000 m during systematic surveys whereas in nonsystematic surveys relative high encounter rates were found in depths of 2,000-2,500m. Most dolphins were found to be distributed in depths <1,000m and at no more than 10 km offshore indicating a preference for shallower waters. Dolphins were sighted during the whole year and there were no significant differences in encounter rate between months. These results suggest the existence of preferential areas for this species based on static bathymetric features. The fact that the dolphins prefer inshore areas that are more exposed to anthropogenic activities should be taken into account when discussing bottlenose dolphin conservation measures in the Madeira archipelago.
- Unraveling site fidelity and residency patterns of sperm whales in the insular oceanic waters of MacaronesiaPublication . Ferreira, Rita; Steiner, Lisa; Martín, Vidal; Fusar-Poli, Francesca; Dinis, Ana; Kaufmann, Manfred; Fernandez, Marc; Alves, Filipe M. A.Knowledge of the distribution and residency of pelagic marine megafauna, particularly deep-diving species, is scarce due to their high mobility over difficult-to-access oceanic areas and long periods underwater. However, the threatened status of many of these species, such as the sperm whale Physeter macrocephalus, increases the need to obtain quantitative data to support conservation measures. In the warm temperate waters of Macaronesia (Eastern North Atlantic), sperm whales occur year-round in a set of island systems (the Azores, Madeira, and the Canaries), mainly in social groups of females and juveniles with the occasional visits of mature males. Although it is known that they perform inter-archipelago movements, information on site fidelity and residency times is still scarce. Here, based on photographic-identification data, site fidelity and residency times of sperm whales were estimated for subareas of the Azores and the Madeira archipelagos, with a preliminary assessment for a subarea of the Canaries. The Azores and Madeira subareas presented similar proportions of individuals with recaptures (~25%), mainly inter-annual, while in the subarea of the Canaries, only <10% of the individuals were recaptured. Standardized Site Fidelity Indexes showed very low values (<0.01) for both the Azores and Madeira subareas. Lagged identification rates based on models including emigration and reimmigration estimated that an average of 44.8 individuals (SE=4.9) spent 12.9 days (SE=1.5) in the Azores before leaving for 99.1 days (SE=12.5), while 8.4 individuals (SE=16.1) spent 0.8 day (SE=6.6) in Madeira before leaving for 8.6 days (SE=6.9), with a very low mortality rate. This study i) indicates a degree of residency of about ¼ of the identified individuals for the Azores and Madeira subareas and ii) supports that these oceanic archipelagos constitute an important habitat for a Vulnerable species in the Atlantic. Moreover, it also highlights the importance of combining data from opportunistic and dedicated surveys and joint national and international efforts toward the conservation of marine megafauna.