Cetacean Diversity Research Articles

Diversity, Distribution, and Density of Marine Mammals Along the Saudi Waters of the Arabian Gulf: Update From a Multi-Method Approach

Despite the important role of marine mammals in marine ecosystems and the imperative for their conservation, there is still a great lack of information on the diversity, distribution, and density of these animals in the Saudi waters of the Arabian Gulf. To fill this gap, an integrative data-collection approach including fishermen’s questionnaires, opportunistic sighting reports, and directed boat-based surveys, was undertaken between 2016 and 2020, leading to the first scientific report of marine mammal diversity, distribution, and density in the region. The results of the different approaches carried out during the study confirmed a high diversity of cetaceans on the west coast of the study area, with bottlenose dolphins (Tursiops aduncus), humpback dolphins (Sousa plumbea) and dugongs (Dugong dugon) as the most common species. While the two dolphin species were found to be widely distributed in both coastal and offshore waters,D. dugonappears to occur exclusively in coastal waters in the southern part of the study area, mainly in the Gulf of Salwah. The presence of both species of dolphins increased during the summer months and in the vicinity of the numerous oil and gas facilities in this region. The distribution of the observed dolphins was found mostly within a 10–20 km radius around each facility. Other cetacean species observed less frequently in the area include Bryde’s whale (Balaenoptera edeni), killer whale (Orcinus orca), common dolphin (Delphinus delphis) and finless porpoise (Neophocaena phocaenoides). Regarding the density of marine mammals in the region, boat-based surveys confirmed the results of fishermen’s questionnaires and reports of opportunistic sightings, with bottlenose and humpback dolphins being the most abundant species. These results provide a baseline for policies oriented to the conservation of mammals in the Saudi waters of the Arabian Gulf.

Shifting baselines of cetacean conservation in Europe

Abstract Within just one human lifetime, the underlying motivation to conserve whales, dolphins and porpoises has shifted from being purely practical and anthropogenic to something much broader, reflecting a desire to protect populations as well as individual animals. In European waters, cetacean conservation currently tends to focus on direct and obvious threats, whereas those originating from widespread human encroachment and consumption patterns tend to be overlooked, even when they are pervasive enough to seriously affect cetacean populations. Cetacean habitat and prey rarely benefit from actual protection (including within Marine Protected Areas), while only moderate and often nominal protection is granted to the cetaceans, without clear conservation baselines and quantitative recovery targets. Meanwhile, historical baselines of cetacean diversity, abundance and distribution appear to be shifting, and the memory of past culling campaigns is fading. Here, we argue that cetacean conservation should go beyond just avoiding further population decline or warding off the extinction of single species. Allowing only the most opportunistic and resilient species to persist, often by merely attempting to mitigate direct mortality (e.g. bycatch in fishing gear), should not pass for actual cetacean conservation. We should strive instead for the full recovery of multiple species throughout their historical ranges.

Cetacean conservation planning in a global diversity hotspot: dealing with uncertainty and data deficiencies

AbstractMany cetacean species are at risk from anthropogenic disturbances including climate change, pollution, and habitat degradation. Identifying cetacean hotspots for conservation management is therefore required. Aotearoa–New Zealand waters are used by 53% of the world’s cetacean species and are a global cetacean diversity hotspot. Using geographic predictions of cetacean taxa, we aimed to identify important areas within New Zealand waters using two methods: estimates of cetacean richness and a spatial prioritization analysis. For both methods, we investigated how varying levels of uncertainty in predictions of the taxa’ occurrence layers would affect our interpretation of cetacean hotspots. Despite some marked spatial differences in distribution of important areas for cetacean diversity, both methods, across all uncertainty scenarios, highlighted six distinct deep offshore regions as important habitat. Generally, inshore areas had lower richness estimates than offshore areas, but these remain important for conservation for species with limited ranges (e.g., the endemic Māui and Hector’s dolphins), and in some places had similar richness values to offshore hotspots. Furthermore, inshore hotspots had lower uncertainty in predicted taxa distribution and richness estimates. The use of two different uncertainty estimates allows the integration of distributional information from differing sources (different modeling methods with varying numbers of cetacean records) to be integrated in a robust and conservative way. Identification of cetacean hotspots with varying levels of uncertainty provides a robust and efficient step toward prioritizing areas for conservation management in a participatory process.

Occurrence, distribution and composition of marine mammals in the bight of Bony, Nigeria

Information on the distribution, occurrence and population structure of cetaceans (whales and dolphins) of the Atlantic coast of Nigeria in West Africa remains fairly sparse to date, with few detailed studies being conducted on this valuable marine resource. This paper highlights the abundant cetacean community sighted in the Nigerian coastal waters and the respective importance of this area as a prime coastal habitat for these mammals. The secondary objective was the evaluation of this resource and development of appropriatemanagement policies. Opportunistic data was collected on board six different marine vessels belonging to some international oil companies (IOC) in Nigeria, whose primary objective was to conduct seismic operations. 8,327 hours and 36 minutes of effort was logged during 2 wet and 3 dry seasons respectively, covering almost 880 km2 at a depth range of 10 to 70 m. The total number of individuals recorded was 2199 of which 80% were dolphins and 20% were whales. Out of these, 55.14% was sighted at depth range of 21 – 30 m. This was followed by 30.42% recorded at depth range of 31 - 40 m. The least frequency of 0.75 % was recorded at depth range of 61- 70m. Five hundred and twenty-five (525) individual whales was recorded, out of which 77.14% were adults and 22.86% were juveniles, while 1674 individual dolphins were recorded with 52.63% juveniles and 47.37% adult. Four species of dolphins were identified. The bottlenose dolphins, Tursiops truncatus was the most abundant owing to the large size of the groups observed, followed by common dolphin, Delphinus delphis. All species of dolphins identified occurred throughout the sampling months. Two species of whales were identified with the humpback whale (Megaptera novaeangliae) predominant and killer whales (Orcinus orca) which seem to be present in just a part of a year. Nigerian coastal water is moderately rich in cetacean diversity, which is currently underreported due to limited research.Keywords: Whales, dolphins, species diversity, opportunistic surveys, Nigeria.

Cetacean occurrence and diversity in whale-watching waters off Mirissa, Southern Sri Lanka.

Scientific information is vital to the conservation of cetaceans and the management of whale-watching activities. The southern coastal waters of Sri Lanka are near a narrow continental shelf and biologically abundant in cetacean species. Although the occurrence of cetaceans has been investigated in certain waters of Sri Lanka, few surveys have been conducted along the southern coast. To fill this gap, we conducted boat-based surveys from January to May 2017 to investigate the occurrence, diversity, and behavior of cetaceans in the waters off Mirissa, covering a survey area of 788.9 km2 . During 55 survey days, we recorded a total of 242 cetacean sightings and identified at least 9 species (3 mysticetes and 6 odontocetes). The blue whale was the most common mysticete species (167 of 174 mysticete encounters), followed by the Omura's whale (4 of 174) and Bryde's whale (3 of 174). The spinner dolphin was the most common odontocete species (28 of 68 odontocete encounters), followed by the sperm whale (18 of 68), common bottlenose dolphin (13 of 68), short-finned pilot whale (5 of 68), melon-headed whale (2 of 68), and killer whale. Blue whales and sperm whales exhibited a clear preference for outer shelf and high slope areas, and blue whales were observed feeding along these waters. The present study provides near-baseline information on cetacean occurrence and diversity in whale-watching waters off southern Sri Lanka, and highlights the urgent need for proper management strategies for whale-watching activities.

Marine soundscape variation reveals insights into baleen whales and their environment: a case study in central New Zealand.

Baleen whales reliably produce stereotyped vocalizations, enabling their spatio-temporal distributions to be inferred from acoustic detections. Soundscape analysis provides an integrated approach whereby vocal species, such as baleen whales, are sampled holistically with other acoustic contributors to their environment. Acoustic elements that occur concurrently in space, time and/or frequency can indicate overlaps between free-ranging species and potential stressors. Such information can inform risk assessment framework models. Here, we demonstrate the utility of soundscape monitoring in central New Zealand, an area of high cetacean diversity where potential threats are poorly understood. Pygmy blue whale calls were abundant in the South Taranaki Bight (STB) throughout recording periods and were also detected near Kaikōura during autumn. Humpback, Antarctic blue and Antarctic minke whales were detected in winter and spring, during migration. Wind, rain, tidal and wave activity increased ambient sound levels in both deep- and shallow-water environments across a broad range of frequencies, including those used by baleen whales, and sound from shipping, seismic surveys and earthquakes overlapped in time, space and frequency with whale calls. The results highlight the feasibility of soundscape analysis to quantify and understand potential stressors to free-ranging species, which is essential for conservation and management decisions.

Cetacean habitat modelling to inform conservation management, marine spatial planning, and as a basis for anthropogenic threat mitigation in Indonesia

Indonesia harbours a high diversity of cetaceans, yet effective conservation is hampered by a lack of knowledge about cetacean spatial distribution and habitat preferences. This study aimed to address this knowledge gap at an adequate resolution to support national cetacean conservation and management planning. Maximum Entropy (Maxent) modelling was used to map the distribution of 15 selected cetacean species in seven areas within Indonesian waters using recent cetacean presence datasets as well as environmental predictors (topographic and oceanographic variables). We then combined the individual species suitable habitat maps and overlaid them with provincial marine spatial planning (MSP) jurisdictions, marine protected areas (MPAs), oil and gas contract areas, and marine traffic density. Our results reflect a great heterogeneity in distribution among species and within species among different locations. This heterogeneity reflects an interrelated influence of topographic variables and oceanographic processes on the distribution of cetacean species. Bathymetry, distance to- coast and the −200m isobaths, and chlorophyll-a concentration and sea surface temperature were important variables influencing distribution of most species in many regions. Areas rich in species were mainly related to coastal areas or insular-reef complexity, representing high productivity and upwelling-modified waters. Although some important suitable habitats currently fall within MPAs, other areas are not and overlap with oil and gas exploration activities and marine traffic, indicating potentially high risk areas for cetaceans. The results of this study can support national cetacean conservation and management planning, and be used to reduce or avoid adverse anthropogenic threats. We advise to consider currently unprotected suitable cetacean habitats in MPA and MSP development.

Integrating morphology and DNA barcoding to assess cetacean diversity in Brazil

Stranded cetaceans (whales, dolphins, and porpoises) are frequently used to obtain data on species occurrence and demographic trends. Accurate species-level identification of these individuals is crucial, but often challenging or impossible when relying solely on morphological features (e.g., for highly decayed specimens). To aid in the development of a reliable molecular assay for cetacean DNA-based identification, we tested the efficacy of the standardized DNA barcode segment of the coxI gene in identifying cetaceans occurring off the Brazilian coast and in its continental waters. We generated coxI sequences from 150 specimens (collected by 16 Brazilian institutions), most of which included voucher material (skulls, skeletons and/or images) deposited in scientific collections. This allowed a direct comparison between their morphological and molecular identification. CoxI sequences correctly identified ~93% of the samples, comprising 33 species (70% of the 47 cetaceans reported for Brazilian waters). Two species (Berardius arnuxii and Phocoena dioptrica) were sequenced for coxI for the first time. For only two dolphins (Stenella coeruleoalba and S. clymene) and a right whale (Eubalaena australis), coxI failed to identify the species due to overlapping distributions of intra- vs. interspecific divergences. Only one right whale species occurs in the southern hemisphere, facilitating identification in this case. Stenella dolphins present extensive sympatry and potential inter-species hybridization, suggesting that nuclear markers may be required for their reliable identification. These results indicate that DNA barcoding can reliably identify most stranded cetaceans and highlight the importance of voucher materials to validate the construction of a reliable DNA-based identification system.

Sebaran dan Keanekaragaman Cetacea saat Musim Timur di Perairan Tejakula, Buleleng, Bali

Cetaceans are marine mammals whose entire life is in marine and fresh waters. Cetaceans consist of whales, dolphins, and porpois. The distribution of cetaceans is a matter that shows the points of emergence of cetaceans in a waters. Diversity index is to determine the diversity of a group by looking at the number of species in a group. The waters of Tejakula Subdistrict are one of the waters in North Bali. The waters of North Bali is one of the waters which has become a migration path for several species of cetaceans. As a cetacean migration pathway, there are many occurrences of cetaceans in the northern waters of Bali. One of the most famous locations for the emergence of cetaceans in Bali is the waters of the Tejakula District, so research on cetaceans in the waters of the Tejakula Subdistrict needs to be done. This study aims to determine the distribution and diversity of cetaceans in the waters of Tejaula District. This research was conducted for 3 months, namely in the months of July, August and September 2017. Research on the distribution of cetaceans was carried out to determine the cetacean emergence points. The types of cetaceans found during the three months of the study were Stenella longirostris, Stenella attenuata, Globicephala macrorhynchus, Steno bredanensis, Lagenodelphis hosei, and Grampus griseus. The diversity of cetaceans in the waters of the Tejakula sub-district in July was 0.55, August 1.24 and September 0.9. The cetacea diversity index in the study area was divided into two, namely the area outside the reserve 1.22 and the area in the reserve 0.55.

Erratum: Cetacean Distribution and Diversity in Lakshadweep Waters, India, Using a Platform of Opportunity: October 2015 to April 2016

Erratum: Cetacean Distribution and Diversity in Lakshadweep Waters, India, Using a Platform of Opportunity: October 2015 to April 2016

Cetacean Distribution and Diversity in Lakshadweep Waters, India, Using a Platform of Opportunity: October 2015 to April 2016

Prior stranding records suggest that at least 12 cetacean species occur within the Lakshadweep archipelago off the southwest coast of India. These islands consist of coral atolls and form the northern part of the undersea Chagos-Laccadive ridge. Distinct oceanographic features, seasonal monsoon cycles, and high productivity make this region a potentially rich cetacean habitat In this article, we report findings from the first systematic visual cetacean surveys, which were conducted from high-speed passenger ferries that sail between nine Lakshadweep islands. The surveys were carried out between October 2015 and April 2016 during both the northeast monsoon (October to December) and inter-monsoon (January to April) seasons. We used a line-transect survey framework to record sightings as well as group size estimates. We documented 139 sightings over 3,880 km of which 78 sightings were during systematic survey effort. Eight odontocete species were confirmed from these sightings: Stenella longirostris, S. attenuata, S. coeruleoalba, Tursiops spp., Globicephala macrorhynchus, Pseudorca crassidens, Grampus griseus, and Feresa attenuata. One Balaenoptera sp. was also encountered during this survey. S. longirostris was sighted the most often (n = 22) followed by Tursiops spp. (n = 18) and G. macrorhynchus (n = 13). We documented significantly higher sightings in the northeast monsoon season compared to the intermonsoon season. Along ferry routes, cetacean species differed significantly from each other with respect to their associations with seafloor slope gradients and distances to nearest landmass. We encountered mixed species assemblages of G. macrorhynchus with Tursiops sp. and S. attenuata with Tursiops sp. Given the confirmed high cetacean diversity and occurrence in this region, there is a need for in-depth, long-term studies on biogeography, ecology, and population status of cetaceans here.

Scientific collaboration networks in research on human threats to cetaceans in Brazil

To better understand the threats posed by human activities on cetaceans, we compiled published studies and determined where, how, and by whom the research on this subject has been conducted in Brazil. We also determined which cetacean species were mostly investigated in these studies. We gathered the available scientific literature published from 1986 to 2016 that contained search terms in English that depicted major cetacean threats. Then, we developed a collaboration network among the authors' institutions and generated a distribution map of the investigated threats and study areas. From the 1047 compiled publications, we selected 103 studies that precisely addressed cetacean threats. The selected studies were carried out by 82 institutions from 12 countries. Most of these institutions were universities (n = 55), followed by non-governmental organizations (n = 15) and research institutes (n = 12). Among the two cetacean suborders, odontocetes were the most representative, with Sotalia guianensis and Pontoporia blainvillei present in 50 and 38 publications, respectively. For mysticetes, publications on Megaptera novaeangliae (n = 6) and Eubalaena australis (n = 5) were the most common. Among the addressed threats, more than half (54.4%) of the publications focused on pollution, followed by bycatch (19.4%) and vessel traffic (10.7%). Most of the study areas took place in the states of Rio de Janeiro (22.4%), São Paulo (19.7%), and Rio Grande do Sul (12.9%). Six institutions were the most prevalent in the collaboration networks, and their location corresponded to hotspots of cetacean diversity. Our findings may contribute to identifying research priorities and guide the conservation of cetacean species in Brazil.

Cetacean biodiversity, spatial and temporal trends based on stranding records (1920-2016), Victoria, Australia.

Cetacean stranding records can provide vital information on species richness and diversity through space and time. Here we collate stranding records from Victoria, Australia and assess them for temporal, spatial and demographic trends. Between 1920 and 2016, 424 stranding events involving 907 individuals were recorded across 31 Cetacea species from seven families, including five new species records for the state. Seven of these events were mass strandings, and six mother and calf strandings were recorded. Importantly, 48% of the species recorded are recognised as data deficient on the IUCN Red List. The most commonly recorded taxa were Tursiops spp. (n = 146) and Delphinus delphis (common dolphins, n = 81), with the greatest taxonomic richness (n = 24) and highest incidence of stranding events documented within the Otways mesoscale bioregion. We found no seasonal stranding patterns anywhere in the state. While our findings improve understanding of the spatial and temporal patterns of cetacean diversity within Victoria, we suggest greater effort to collect demographic data at stranding events in order to better study state-wide patterns through time. We conclude with guidelines for minimum data collection standards for future strandings to maximise information capture from each event.

Cetacean biodiversity in the Bay of Biscay: Suggestions for environmental protection derived from citizen science data

Cetacean communities face significant threats from adverse interactions with human activities such as bycatch, vessel collision, and environmental pollution. Monitoring of marine mammal populations can help to assess and safeguard marine biodiversity for future generations. Traditional surveys can be costly and time-consuming to undertake, but we explore the ability of citizen science to inform environmental assessments and subsequent conservation management. We use data collected from platforms of opportunity within the Bay of Biscay to investigate spatial changes in cetacean diversity, with the aim of identifying hotspots which may be suitable for further investigation and conservation. Seventeen species of cetaceans were recorded over a ten year period, many of which are data deficient in European waters (e.g. Bottlenose dolphin, Short-beaked common dolphin, Striped dolphin, Risso's dolphin, Long-finned pilot whale, Killer whale, Northern bottlenose whale, Cuvier's beaked whale, Sowerby's beaked whale and True's beaked whale). Biodiversity (determined by Simpson's Diversity index) ranged from 0.19 to 0.77. The central and southern areas of the survey area indicated the highest biodiversity (0.65–0.77), and these locations may benefit most from protection as Important Marine Mammal Areas. We present a case for this designation, and discuss the benefits and limitations of citizen science for informing conservation action.

Fat Embolism and Sperm Whale Ship Strikes

Strikes between vessels and cetaceans have significantly increased worldwide in the last decades. The Canary Islands archipelago is a geographical area with an important overlap of high cetacean diversity and maritime traffic, including high-speed ferries. Sperm whales (Physeter macrocephalus), currently listed as a vulnerable species, are severely impacted by ship strikes. Nearly 60% of sperm whales’ deaths are due to ship strikes in the Canary Islands. In such cases, subcutaneous, muscular and visceral extensive hemorrhages and hematomas, indicate unequivocal antemortem trauma. However, when carcasses are highly autolysed, it is challenging to distinguish whether the trauma occured ante- or postmortem. The presence of fat emboli within the lung microvasculature is used to determine a severe “in vivo” trauma in other species. We hypothesized fat emboli detection could be a feasible, reliable and accurate forensic tool to determine ante-mortem ship strikes in stranded sperm whales, even in decomposed carcasses. In this study, we evaluated the presence of fat emboli by using an osmium tetroxide (OsO4) based histochemical technique in lung tissue of 24 sperm whales, 16 of them with evidence of ship strike, stranded and necropsied in the Canaries between 2000 and 2017. About 70% of them presented an advanced autolysis. Histological examination revealed the presence of OsO4-positive fat emboli in 13 out of the 16 sperm whales with signs of ship strike, and two out of eight of the ‘control’ group, with varying degrees of abundance and distribution. A classification and regression tree was developed to assess the cut off of fat emboli area determining the high or low probability for diagnosing ship-strikes, with a sensitivity of 89% and a specifity of 100%.The results demonstrated: 1) the usefulness of fat detection as a diagnostic tool for “in vivo” trauma, even in decomposed tissues kept in formaldehyde for long periods of time; and 2) that, during this 18-year period, at least, 81% of the sperm whales with signs of ship strike were alive at the moment of the strike and died subsequently. This information is highly valuable in order to implement proper mitigation measures in this area.

What can cetacean stranding records tell us? A study of UK and Irish cetacean diversity over the past 100 years

AbstractThere are many factors that may explain why cetaceans (whales, dolphins, and porpoises) strand. Around the UK and Ireland, over 20,000 stranding records have been collected since 1913, resulting in one of the longest, continuous, systematic stranding data sets in the world. We use this data set to investigate temporal and spatial trends in cetacean strandings and use generalized additive models (GAMs) to investigate correlates of strandings. We find a dramatic increase in strandings since the 1980s, most likely due to increases in recording effort, and the formation of formal strandings networks. We found no correlation between the numbers of cetaceans stranding each year and several potential environmental and anthropogenic predictors: storms, geomagnetic activity, North Atlantic Oscillations, sea‐surface temperature, and fishing catch. We suggest that this is because the scale of change in the variables is too coarse to detect any potential correlations. It may also highlight the idiosyncratic nature of species’ responses to external pressures, and further the need to investigate other potential correlates of strandings, such as bycatch and military sonar. Long‐term cetacean stranding data provide vital information on past and present diversity for common, rare, and inconspicuous species. This study underlines the importance of continued support for stranding networks.

Can local ecological knowledge provide meaningful information on coastal cetacean diversity? A case study from the northern South China Sea

Identifying and evaluating potentially suitable tools to assess the status of cetaceans in coastal waters with high levels of anthropogenic threat represents a first step towards effective conservation management. Local ecological knowledge (LEK) can often provide more extensive information on focal species and biological resources than is available from standard ecological surveys, and is increasingly recognized as an important source of data for conservation research and management, but it has rarely been used as a tool to assess the status of cetaceans. We investigated the efficacy of using LEK from local fishers combined with stranding records to characterise the diversity and distribution of coastal cetaceans in the northern South China Sea, a region with high historical levels of cetacean abundance and diversity but which is experiencing intensifying anthropogenic pressures. Fishers were unable to identify most regionally occurring cetaceans to species level. However, we were able to determine the distributions of eight categories of cetaceans that were observed by fishers, and a previously unknown population of Indo-Pacific humpback dolphin reported from the coastal waters of Hainan that was later confirmed through boat-based surveys. The number of sightings of different cetacean categories reported by fishers has a significant positive linear relationship with independent data on numbers of stranded cetaceans, validating the accuracy of our respondent data and indicating that LEK can provide useful, quantitative information on abundance rankings of different cetacean categories.

Cetacean Diversity Revealed from Whale-Watching Observations in Northern Peru

Cetacean Diversity Revealed from Whale-Watching Observations in Northern Peru

The energetics of 'airtime': estimating swim power from breaching behaviour in fishes and cetaceans.

Displays of maximum swimming speeds are rare in the laboratory and the wild, limiting our understanding of the top-end athletic capacities of aquatic vertebrates. However, jumps out of the water - exhibited by a diversity of fish and cetaceans - might sometimes represent a behaviour comprising maximum burst effort. We collected data on such breaching behaviour for 14 fish and cetacean species primarily from online videos, to calculate breaching speed. From newly derived formulae based on the drag coefficient and hydrodynamic efficiency, we also calculated the associated power. The fastest breaching speeds were exhibited by species 2 m in length, peaking at nearly 11 m s-1; as species size decreases below this, the fastest breaches become slower, while species larger than 2 m do not show a systematic pattern. The power associated with the fastest breaches was consistently ∼50 W kg-1 (equivalent to 200 W kg-1 muscle) in species from 20 cm to 2 m in length, suggesting that this value may represent a universal (conservative) upper boundary. And it is similar to the maximum recorded power output per muscle mass recorded in any species of similar size, suggesting that some breaches could indeed be representative of maximum capability.

Living apart together: Niche partitioning among Alboran Sea cetaceans

Co-occurring species are expected to distribute themselves unevenly throughout ecological niche dimensions to avoid competitive exclusion. However, few studies have previously investigated spatial and trophic factors structuring an entire cetacean community. Here, we combined density surface models (DSMs) with two dimension (δ15N and δ13C) isotopic niche spaces in order to identify the mechanistic processes underlying niche partitioning for the most abundant cetacean species inhabiting the Alboran Sea: the long-finned pilot whale (Globicephala melas), the Cuvier’s beaked whale (Ziphius cavirostris), the Risso’s dolphin (Grampus griseus), the bottlenose dolphin (Tursiops truncatus), the striped dolphin (Stenella coeruleoalba), and the short-beaked common dolphin (Delphinus delphis). DSMs provide a spatially-explicit assessment of species distribution through key spatial and environmental gradients, whereas isotopic niches characterize habitat and resource use. Our isotopic niche approach pointed to habitat and/or trophic segregation between the small (striped and short-beaked common dolphins) and large-sized cetacean species (Risso’s and bottlenose dolphins, and long-finned pilot whales). Conversely, DSMs suggested a larger degree of spatial segregation among species by depth, with some overlap for offshore species (long-finned pilot, Cuvier’s beaked whales and Risso’s dolphins) and also between bottlenose and common dolphins. Thus, both components of the ecological niche apparently played an important role in explaining niche partitioning among species, which, in turn, might explain the high abundance and diversity of cetaceans in the Alboran Sea. Further, when both methodologies were applied in isolation, the structure and functioning of this cetacean community was poorly resolved. The combination of both approaches is therefore desirable when investigating niche partitioning among ecologically similar species within communities.