Tursiops Research Articles

Comparison of de novo assembly using long-read shotgun metagenomic sequencing of viruses in fecal and serum samples from marine mammals.

Viral diseases of marine mammals are difficult to study, and this has led to a limited knowledge on emerging known and unknown viruses which are ongoing threats to animal health. Viruses are the leading cause of infectious disease-induced mass mortality events among marine mammals. In this study, we performed viral metagenomics in stool and serum samples from California sea lions (Zalophus californianus) and bottlenose dolphins (Tursiops truncates) using long-read nanopore sequencing. Two widely used long-read de novo assemblers, Canu and Metaflye, were evaluated to assemble viral metagenomic sequencing reads from marine mammals. Both Metaflye and Canu assembled similar viral contigs of vertebrates, such as Parvoviridae, and Poxviridae. Metaflye assembled viral contigs that aligned with one viral family that was not reproduced by Canu, while Canu assembled viral contigs that aligned with seven viral families that was not reproduced by Metaflye. Only Canu assembled viral contigs from dolphin and sea lion fecal samples that matched both protein and nucleotide RefSeq viral databases using BLASTx and BLASTn for Anelloviridae, Parvoviridae and Circoviridae families. Viral contigs assembled with Canu aligned with torque teno viruses and anelloviruses from vertebrate hosts. Viruses associated with invertebrate hosts including densoviruses, Ambidensovirus, and various Circoviridae isolates were also aligned. Some of the invertebrate and vertebrate viruses reported here are known to potentially cause mortality events and/or disease in different seals, sea stars, fish, and bivalve species. Canu performed better by producing the most viral contigs as compared to Metaflye with assemblies aligning to both protein and nucleotide databases. This study suggests that marine mammals can be used as important sentinels to surveil marine viruses that can potentially cause diseases in vertebrate and invertebrate hosts.

Cardiorespiratory coupling in the bottlenose dolphin (Tursiops truncatus).

Introduction: The bottlenose dolphin (Tursiops truncatus) is an intermittent breather, where the breath begins with an exhalation followed by inhalation and an extended inter-breath interval ranging from 10 to 40s. Breathing has been shown to alter both the instantaneous heart rate (if H) and stroke volume (iSV) in the bottlenose dolphin, with a transitory ventilatory tachycardia following the breath, and an exponential decrease to a stable if H around 40 beats • min-1 during the inter-breath period. As the total breath duration in the dolphin is around 1s, it is not possible to assess the contribution of exhalation and inhalation to these changes in cardiac function during normal breathing. Methods: In the current study, we evaluated the if H response by separating expiration and inspiration of a breath, which allowed us to distinguish their respective contribution to the changes in if H. We studied 3 individual male bottlenose dolphins trained to hold their breath between the different respiratory phases (expiration and inhalation). Results: Our data show that inspiration causes an increase in if H, while expiration appears to result in a decrease in if H. Discussion: These data provide improved understanding of the cardiorespiratory coupling in dolphins, and show how both exhalation and inhalation alters if H.

Assessing of the use of proteins A, G, and chimeric protein AG to detect marine mammal immunoglobulins.

In recent years, there has been an increase in infectious diseases in marine mammals, including brucellosis, infections of morbillivirus, herpesvirus, and poxvirus. Several serological diagnostic methods, including enzyme-linked immunosorbent assays, immunofluorescence assays (ELISA), and western blotting, have been used to detect antibodies against pathogens in marine mammals. However, options for commercial secondary antibodies used to detect antibodies in marine mammals are limited; therefore, the use of proteins A, G, or chimeric protein AG may provide a suitable alternative. This study aimed to assess the use of proteins A, G, and chimeric protein AG to detect marine mammal immunoglobulins. Currently, there are no comparative studies on the use of proteins A, G, and chimeric protein AG for the detection of immunoglobulins in marine mammals. In this study, we used ten pinnipeds' species (Baikal seal, California sea lion, harbor seal, northern fur seal, ringed seal, South American fur seal, South American sea lion, spotted seal, Steller sea lion, and walrus) and five cetacean species (beluga whale, bottlenose dolphin, harbor porpoise, killer whale, and Pacific white-sided dolphin) and compare binding ability to proteins A, G, or chimeric protein AG by ELISA. The results revealed that the immunoglobulins from pinniped and cetacean species reacted more strongly to protein A than protein G. In addition, the immunoglobulins of pinnipeds and cetaceans showed a strong binding ability to chimeric protein AG. These results suggest that proteins A, G, and chimeric protein AG would be used to help further develop serological assays.

Assessing spatial patterns and density of a dolphin population through signature whistles

AbstractSome dolphin species produce signature whistles, which may allow the identification of individual dolphins using passive acoustic monitoring (PAM). Identifying individuals by their sounds may enhance the opportunities for monitoring and addressing biological and ecological questions about these species. Here, we explored the potential of signature whistles to investigate ecological aspects of a resident bottlenose dolphin population. Using a limited data set, with few individuals recognized by signature whistles, combined with spatial capture‐recapture (SCR) methods, we investigated how effective such approach is describing spatial use patterns and estimating density for this population. The data were collected using 4–6 stationary bottom‐moored recorders. Since only eight signature whistles were identified, our density estimate may represent a subset of the entire population. However, even with only a few signature whistles identified, our results confirmed the center of the core area used by these dolphins as the area with the highest encounter probability. In addition, our results provided evidence that these dolphins have the same spatial use pattern at night as during the day. This study shows that SCR analysis of signature whistle data can improve our ecological knowledge and understanding of dolphin populations.

Records of atypical pigmented bottlenose dolphins (Tursiops truncatus) at the south-western coast of the Black Sea (Zonguldak, Türkiye)

Records of atypical pigmented bottlenose dolphins (Tursiops truncatus) at the south-western coast of the Black Sea (Zonguldak, Türkiye)

Occurrence, abundance and some ecological aspects of the offshore bottlenose dolphin off Ecuador’s central coast

The presence of the offshore bottlenose dolphin (Tursiops truncatus) is poorly understood for most of the southeast Pacific Ocean. Its wide distribution, low density, and lack of understanding of its ecology make the species unpredictable to observe and difficult to study compared to the coastal ecotype. We assessed the occurrence of offshore bottlenose dolphins off the central coast of Ecuador (01°36’ S, 80°58’ W) using information taken from 2001 to 2022. Data were collected by two research groups based 80 km apart, one in Puerto López (north) and the other in Salinas (south). A total of 48 dolphin groups were documented, 22 at Puerto López and 26 at Salinas. In Puerto López, 163 dolphins were individually identified, of which 70 intra-annual sightings and 102 inter-annual sightings were found. Inter-annual resightings at Puerto López corresponded to 55 individuals (33.7%) recorded between two and 17 years (mean = 5.82 years, SD = 5.1). In Salinas, 58 dolphins were identified, without intra-annual resightings and only two inter-annual sightings. Only one individual was recorded in both areas. Two site fidelity indexes were calculated, Occurrence (Oi) and Permanence (Pi), resulting in 11 and 13.7 times higher respectively, in Puerto López. The abundance at Puerto López, 163 animals (95% CI, 120 - 203) in 2021-2022, was estimated with a closed population model. The prevalence of scars associated with previous encounters with fishing gear was 43.6%, commensal barnacle (Xenobalanus globicipitis) infestation 42.3%, predation 3.6%, and dermal nodules 0.61%. Our findings suggest both site fidelity and some degree of population structure, but additional monitoring and genetic studies are needed to clarify these aspects. Nevertheless, this study provides information on key aspects necessary for developing conservation strategies for offshore bottlenose dolphins.

Investigating fishery and climate change effects on the conservation status of odontocetes in the Northern Ionian Sea (Central Mediterranean Sea)

A modelling approach applied to the study of ecosystems from a management and conservation point of view allows their complexity to be investigated and represents a tool for meeting sustainability goals, part of the 2030 Agenda for Sustainable Development. Tying into Sustainable Development Goals (SDGs) 13 and 14, the human activities of fisheries and climate change represent two pivotal drivers for the marine environment, acting on keystone predators, such as odontocetes. A calibrated time-dynamic model (Ecopath with Ecosim) was developed to investigate the effects on the odontocetes and their main prey in the Northern Ionian Sea (Central Mediterranean Sea), according to changes in trawl fishery and primary productivity. In particular, the food web of the Gulf of Taranto (GoT) is described by 51 functional groups (FGs), with four odontocetes (striped, common bottlenose, Risso's dolphin and sperm whale) represented as a single FG, and 5 fishing fleets. The calibration of the Ecosim model was carried out during the period 2009–2018 using a combination of automatic and manual fitting procedures. Changes in trawling fishing effort (increases, reductions and bans) and in primary production were tested in the period until to 2040 to detect the effect on the biomass of odontocetes and their main prey. The cumulative effects of the two drivers were assessed using an Interaction Effect Index. Fishery showed negligible effects on all odontocetes, with the exception of the common bottlenose dolphin which respond in a negative way to an increase in fishing effort. The reduction in top-predators due to fishing seems to lead to a reduction in predation pressure on meso‑consumers, and thus to an increase in predation pressure on basal prey. Similarly, the bottom-up effect due to increased primary production tends to be diluted towards the top of the trophic network, with slight effects on odontocetes. The trophic interaction pattern tends to mediate the effects tested in the model with a variety of different outcomes on prey. The application of the interaction effects index could contribute to disentangling the effects of fishing and climate on the food web, providing information to address the analysis required by the SDG 14 targets.

Associations and ranging patterns of common bottlenose dolphins near Brunswick, Georgia, USA

AbstractThe Southern Georgia Estuarine System (SGES) stock of common bottlenose dolphins (Tursiops truncatus) resides in estuarine waters near Brunswick, Georgia, USA. There are concerns for this population due to the presence of anthropogenic stressors, particularly in the Turtle‐Brunswick River Estuary (TBRE), where polychlorinated biphenyl (PCB) concentrations in dolphins are >10 times higher relative to dolphins elsewhere in the southeastern United States. The goal of this study was to evaluate the association patterns and distribution of the SGES stock based on long‐term photo‐identification data (2010–2021) using analyses of social dynamics and spatial movements. Social analyses identified 5 distinct clusters, 3 of which were substantially larger and more well‐defined than the other 2. Spatial analyses indicated geographic partitioning among the 3 large clusters, with little overlap in their core ranges (50% utilization distributions) but shared ranges in their 95% utilization distributions. Despite having variable ranging patterns, all 3 large clusters used the TBRE in proximity to the Linden Chemicals and Plastics (LCP) Superfund site to a degree, suggesting that they have likely been exposed to high levels of PCBs. Given the spatial distinction and low connectivity between clusters, loss in any of the identified clusters has potential to further segment the population and lead to a decline in the SGES stock as a whole. The fine‐scale population structure should be considered in identifying effective conservation efforts at the appropriate scale.

Encounter rate and relative abundance of eight cetaceans off the central Catalan coast (Northwestern Mediterranean sea)

This study provides information on cetacean occurrence in the central Catalan coast (NE Iberian Peninsula), an area characterised by an underwater canyon system. Encounter rates (ER), relative abundances (RA) and seasonality were assessed for eight species. This information was combined with physiographic features of the seafloor to understand their influence on cetacean distribution. Data were collected along 189 surveys from January 2017 to December 2022. In total, 479 sightings of eight species of cetaceans were recorded. Striped, bottlenose and Risso's dolphins and fin whales were the most frequently sighted. ER and RA were similar or higher than in other areas of the Mediterranean Sea. Species were distributed differently according to physiographic features: bottlenose dolphins in coastal waters and Risso's dolphins and fin whales above the Garraf underwater canyon system. These results highlight the importance of the central Catalan coast, particularly the underwater canyon system, for at least four species of cetaceans.

The prefrontal cortex of the bottlenose dolphin (Tursiops truncatus Montagu, 1821): a tractography study and comparison with the human.

Cetaceans are well known for their remarkable cognitive abilities including self-recognition, sound imitation and decision making. In other mammals, the prefrontal cortex (PFC) takes a key role in such cognitive feats. In cetaceans, however, a PFC could up to now not be discerned based on its usual topography. Classical in vivo methods like tract tracing are legally not possible to perform in Cetacea, leaving diffusion-weighted imaging (DWI) as the most viable alternative. This is the first investigation focussed on the identification of the cetacean PFC homologue. In our study, we applied the constrained spherical deconvolution (CSD) algorithm on 3T DWI scans of three formalin-fixed brains of bottlenose dolphins (Tursiops truncatus) and compared the obtained results to human brains, using the same methodology. We first identified fibres related to the medio-dorsal thalamic nuclei (MD) and then seeded the obtained putative PFC in the dolphin as well as the known PFC in humans. Our results outlined the dolphin PFC in areas not previously studied, in the cranio-lateral, ectolateral and opercular gyri, and furthermore demonstrated a similar connectivity pattern between the human and dolphin PFC. The antero-lateral rotation of the PFC, like in other areas, might be the result of the telescoping process which occurred in these animals during evolution.

Observed trends in scavenging by common bottlenose dolphins (Tursiops truncatus truncatus) in for‐hire fisheries in the eastern U.S. Gulf of Mexico

AbstractInteractions between bottlenose dolphin and recreational rod and reel fisheries are a complex issue for resource managers in the United States, which may impact anglers' catch and lead to dangerous situations for scavenging or depredating dolphins. To examine this issue, we analyzed data collected by observers on for‐hire fishing vessels off the eastern U.S. Gulf Coast from 2009 to 2020. A generalized additive model indicated number of anglers, number of discarded fish, proximity to shore, prior scavenging events, type of released fish, and area fished were all significant predictors of scavenging by dolphins. The Florida panhandle had the highest odds of scavenging, while scavenging in the Big Bend and Tampa Bay has increased through time. The Florida panhandle is a well‐known area for illegal feeding of dolphins, suggesting human behavior may be influencing fisheries interactions. Model outputs indicate that dolphins are primarily cuing on fishing activity rather than number of discards, but are more likely to scavenge discards from the family Lutjanidae (snappers), which comprised 40% of observed discards but 80% of scavenging events. This study highlights factors influencing the frequency of dolphin scavenging events, guiding managers and scientists on additional studies and mitigation measures needed to address this issue.

Proteomics as a Metrological Tool to Evaluate Genome Annotation Accuracy Following De Novo Genome Assembly: A Case Study Using the Atlantic Bottlenose Dolphin (Tursiops truncatus).

The last decade has witnessed dramatic improvements in whole-genome sequencing capabilities coupled to drastically decreased costs, leading to an inundation of high-quality de novo genomes. For this reason, the continued development of genome quality metrics is imperative. Using the 2016 Atlantic bottlenose dolphin NCBI RefSeq annotation and mass spectrometry-based proteomic analysis of six tissues, we confirmed 10,402 proteins from 4711 protein groups, constituting nearly one-third of the possible predicted proteins. Since the identification of larger proteins with more identified peptides implies reduced database fragmentation and improved gene annotation accuracy, we propose the metric NP10, which attempts to capture this quality improvement. The NP10 metric is calculated by first stratifying proteomic results by identifying the top decile (or 10th 10-quantile) of identified proteins based on the number of peptides per protein and then returns the median molecular weight of the resulting proteins. When using the 2016 versus 2012 Tursiops truncatus genome annotation to search this proteomic data set, there was a 21% improvement in NP10. This metric was further demonstrated by using a publicly available proteomic data set to compare human genome annotations from 2004, 2013 and 2016, which showed a 33% improvement in NP10. These results demonstrate that proteomics may be a useful metrological tool to benchmark genome accuracy, though there is a need for reference proteomic datasets across species to facilitate the evaluation of new de novo and existing genome.

Inferring odontocete life history traits in dentine using a multiproxy approach (δ15 N, δ44/42 Ca and trace elements).

Understanding the interactions between marine mammals and their environment is critical for ecological and conservation purposes. Odontocetes offer a continuous record of their life history from birth as recorded in annual increments of their tooth dentine. Because dentine is not remodeled and contains collagen, nitrogen stable isotope compositions (δ15 N) reflect nursing and weaning events, life history traits that would otherwise be impossible to retrieve in such elusive marine animals. Yet, capturing the magnitude and temporal changes in these events is constrained by tooth size and sampling resolution. Moreover, historical and fossil specimens undergo collagen decay, hence the need to develop the measurements of other proxies. Here, we present a multiproxy approach to investigate the use of Ca isotope compositions (δ44/42 Ca) in relation to δ15 N and laser ablation profiles for different trace metal (Ba, Mg, Sr, Zn) concentrations across the dentine of a single individual of the common bottlenose dolphin Tursiops truncatus. To help interpret the dentine data, we provide milk elemental compositions and δ44/42 Ca values for two odontocete individuals. We discuss the observed changes in δ44/42 Ca across the dentine as potential markers of birth, weaning interval, incidental ingestion of seawater, trophic level and physiology. Incidental ingestion of seawater during nursing induces a positive offset in δ44/42 Ca values recorded in the early formed dentine. Life history parameters of individual marine mammals are extremely difficult to retrieve due to limitations in observing specimens in the wild and the methodology presented here offers new ecological and paleoecological perspectives.

Improving Marine Megafauna Knowledge with eDNA: A French Story

In the current context of large-scale biodiversity loss (Díaz et al. 2019), it is urgent to carry out biodiversity inventories in order to investigate spatial and temporal variations. Among the available methods, environmental DNA (eDNA) (Taberlet et al. 2018) combined with molecular metabarcoding (Valentini et al. 2009) bring new insights in drafting inventories of taxa present in an environment. Approaches based on eDNA facilitate the study of remote ecosystems and the detection of rare, cryptic or invasive species in a non-invasive way (Bohmann et al. 2014). In the marine realm, the study of mobile fauna, including mammals particularly, can greatly benefit from these new techniques. Here, we present a case study carried out in the northeast and northwest Atlantic, within the boundaries of marine protected areas. The Iroise Natural Marine Park*1 was the first French marine natural park created in France in 2007 (Fig. 1). The first campaign in the Iroise Natural Marine Park successfully detected several species of cetacean (e.g., Lagenorhynchus albirostris, Lagenorhynchus obliquidens) and four species of elasmobranchs (e.g., Scyliorhinus canicula, Torpedo marmorata, Raja undulata and Mustelus asterias). This study was extended to the Martinique Natural Marine Park*2, where similar analyses identified three cetacean species (Stenella attenuata, Lagenodelphis hosei and Tursiops truncatus) and 193 teleost taxa (Riou 2022), representing more than half of the species expected in Martinique. The analyses carried out in Martinique highlighted several remarkable sites for fish biodiversity. In Guadeloupe, in the heart of the Agoa Marine Mammals Sanctuary*3 (corresponding to the French Antilles exclusive economic zone), the taxonomic composition of different eDNA samples made in 2021 and 2022 was compared. The samples were analyzed using different primer sets, specific to vertebrates, teleosts and mammals. Comparison of the results obtained with vertebrate-specific primers and those specific to teleosts showed complementary results. For cetaceans, the analyses distinguished ten distinct cetacean taxonomic units and at least 3 distinct species from four samples. In addition, the eDNA samples were used to discriminate between the two recently recognised bottlenose dolphin ecotypes, based on the observation of a fixed nucleotide difference on the barcode targeted by the mammal-specific primers. New primers are currently being developed to make it easier to distinguish species of Delphinidae, which are still complex to identify. Environmental DNA and metabarcoding offer new possibilities for the inventories of marine megafauna and support adequate conservation decision-making processes. It is a major step towards better monitoring of marine mammal populations of the Atlantic Ocean. Moreover, our datasets will be freely available through open platforms following the FAIR (Findable, Accessible, Interoperable, and Reusable) principles.

Cetaceans of the Saya de Malha bank region, Indian Ocean: A candidate Important Marine Mammal Area

The banks of Saya de Malha and the surrounding Mascarene Plateau in the Indian Ocean are among the least studied shallow sea water regions in the world. The steep sloping bathymetry of this region is thought to drive high levels of primary productivity and support a diverse range of marine species. Until now, no surveys for cetaceans have been conducted in the waters surrounding Saya de Malha, and so the diversity of cetaceans is unknown. Opportunistic visual and acoustic surveys for cetaceans were conducted onboard a platform of opportunity, the MY Arctic Sunrise, which was involved in a wider project to document the marine life in the region. Survey effort was conducted over 7,700 km, with twelve species of cetacean encountered, including Bryde’s, sperm, beaked and killer whales, along with spinner, striped, pantropical spotted and bottlenose dolphins. A match of a sperm whale coda vocalisation to another, well-studied population off the coast of Mauritius suggests possible connectivity between these regions although further data would be required to confirm this. The banks of Saya de Malha appear to support a diverse range of cetacean species and further systematic surveys are required to increase our understanding of how different species utilise the banks. We provide whistle contours from visually confirmed acoustic detections to contribute towards building a region-specific whistle classifier. Given the diversity of species detected in the region, we suggest that the Saya de Malha bank area be designated, either as an Important Marine Mammal Area or as a marine protected area.

Breast Milk Oligosaccharides Contain Immunomodulatory Glucuronic Acid and LacdiNAc

Breast milk is abundant with functionalized milk oligosaccharides (MOs) to nourish and protect the neonate. Yet we lack a comprehensive understanding of the repertoire and evolution of MOs across Mammalia. We report ∼400 MO-species associations (>100 novel structures) from milk glycomics of nine mostly understudied species: alpaca, beluga whale, black rhinoceros, bottlenose dolphin, impala, L'Hoest's monkey, pygmy hippopotamus, domestic sheep, and striped dolphin. This revealed the hitherto unknown existence of the LacdiNAc motif (GalNAcβ1-4GlcNAc) in MOs of all species except alpaca, sheep, and striped dolphin, indicating the widespread occurrence of this potentially antimicrobial motif in MOs. We also characterize glucuronic acid-containing MOs in the milk of impala, dolphins, sheep, and rhinoceros, previously only reported in cows. We demonstrate that these GlcA-MOs exhibit potent immunomodulatory effects. Our study extends the number of known MOs by >15%. Combined with >1900 curated MO-species associations, we characterize MO motif distributions, presenting an exhaustive overview of MO biodiversity.

Collective decision‐making in aquatic mammals

ABSTRACT Collective decision‐making is an essential part of day‐to‐day life for group‐living animals. These decisions can be unshared (e.g. leadership) or shared (e.g. consensus). Aquatic mammals face particular challenges when making collective decisions, including a three‐dimensional habitat that can make group coordination and collective navigation a challenge. We systematically reviewed literature on decision‐making in non‐human mammals by examining the types of collective decisions observed and hypotheses used to structure analyses. Most of the current literature was centred around terrestrial species, particularly within primates and artiodactyls. There are no collective decision‐making studies on aquatic mammal species outside of cetaceans. Both unshared and shared decision‐making have been reported in whales and dolphins, with leadership found in killer whales Orcinus orca and bottlenose dolphins Tursiops sp. and consensus decisions in sperm whales Physeter macrocephalus. Five recommendations for decision‐making research include: 1) clearly delineating the temporal components of decision‐making, 2) standardising research to allow for comparisons, 3) considering both shared and unshared decision‐making, 4) analysing decision‐making across behavioural contexts, and 5) avoiding anthropomorphic terminology. Future studies of collective decision‐making will help us better understand how non‐human mammals overcome environmental and contextual challenges – particularly in the case of aquatic species such as cetaceans, which face challenges related to their aquatic environment and exhibit phenomena such as mass strandings.

Using integrated multispecies occupancy models to map co‐occurrence between bottlenose dolphins and fisheries in the Gulf of Lion, French Mediterranean Sea

In the Mediterranean Sea, interactions between marine species and human activities are prevalent. The coastal distribution of bottlenose dolphins Tursiops truncatus and the predation pressure they put on fishing stocks lead to regular interactions with fisheries. Multispecies occupancy models are a relevant framework to estimate co‐occurrence between two (or more) species while accounting for false negatives and potential interspecific dependance although requiring substantial quantity of data to fit. Here, we extended multispecies occupancy model to integrate multiple datasets to map spatial co‐occurrence between trawlers and bottlenose dolphins in the Gulf of Lion, French Mediterranean Sea combining data from aerial surveys and boat surveys at a large spatial scale. The integrated multispecies occupancy model produced more precise estimate than single‐dataset multispecies occupancy models. Our results support that both integrated and multispecies frameworks are relevant to map distribution and understand species interactions in our case study. Besides, our application of multispecies occupancy models to bottlenose dolphins and fishing trawlers enabled to map co‐occurrence probability, which open promising avenues in the understanding of interactions between human activities and marine mammals that occur at large spatial scales.

Gut bacterial communities in Atlantic bottlenose dolphins (Tursiops truncatus) throughout a disease-driven (Morbillivirus) unusual mortality event.

Gut microbiomes are important determinants of animal health. In sentinel marine mammals where animal and ocean health are connected, microbiome impacts can scale to ecosystem-level importance. Mass mortality events affect cetacean populations worldwide, yet little is known about the contributory role of their gut bacterial communities to disease susceptibility and progression. Here, we characterized bacterial communities from fecal samples of common bottlenose dolphins, Tursiops truncatus, across an unusual mortality event (UME) caused by dolphin Morbillivirus (DMV). 16S rRNA gene sequence analysis revealed similar diversity and structure of bacterial communities in individuals stranding before, during, and after the 2013-2015 Mid-Atlantic Bottlenose Dolphin UME and these trends held in a subset of dolphins tested by PCR for DMV infection. Fine-scale shifts related to the UME were not common (10 of 968 bacterial taxa) though potential biomarkers for health monitoring were identified within the complex bacterial communities. Accordingly, acute DMV infection was not associated with a distinct gut bacterial community signature in T. truncatus. However, temporal stratification of DMV-positive dolphins did reveal changes in bacterial community composition between early and late outbreak periods, suggesting that gut community disruptions may be amplified by the indirect effects of accumulating health burdens associated with chronic morbidity.

Skin conditions, epizoa, ectoparasites and emaciation in cetaceans in the Strait of Gibraltar: An update for the period 2016-2020.

ABSTRACT: Cetacean populations in the Strait of Gibraltar are heavily impacted by human activities. Photographs are a valuable tool to monitor the external health of cetaceans. We visually screened 27,866 pictures taken during whale watching operations in the years 2016–2020 for abnormal conditions, such as emaciation, dermal diseases and epizoic infestations. Prevalence levels could not be calculated as data were obtained opportunistically. Dermal diseases were detected in 566 sightings and occurred in all species. Bottlenose dolphins were most strongly affected (n = 192). Hypopigmented skin lesions were most common in all species (n = 291). Tattoo skin disease‐like lesions affected 16 animals (T. truncatus: n = 12; G. melas: n = 3; D. delphis: n = 1). Other observed conditions include expansive annular lesions in three juvenile pilot whales. Furthermore, we report the presence of open wounds in 28 animals (G. melas: n = 23; T. truncatus: n = 2; P. macrocephalus: n = 3). In three pilot whales, these wounds did not heal over a period of several years. Epizoic and ectoparasitic infestations include the observation of Xenobalanus spp. and Pennella balaenopterae. Multiple fin whales were sighted with very high numbers of Pennella balaenopterae, ranging up to 84 parasites per host. Emaciation was mainly detected in bottlenose dolphins (n = 36) and seemed to affect these animals more severely during specific years, potentially indicating fluctuations in prey availability. KEYWORDS: CETACEANS; DERMAL DISEASES; EMACIATION; ECTOPARASITES; STRAIT OF GIBRALTAR