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The southern right whale dolphin, Lissodelphis peronii (Lacépède, 1804), is a species of cetacean that is distributed in cold and deep waters throughout the Southern Hemisphere, with records in coastal waters of the western Atlantic Ocean being extremely rare. On January 7, 2019, a specimen still alive, was recorded entangled in a fishing gillnet on the beach at Cardoso Beach (28°44′S, 48°58′W), in the state of Santa Catarina, on the southern coast of Brazil. The recording was made by a lifeguard using a GoPro camera and was made available through citizen science. The animal was untangled and released while still alive and was not found stranded again after the date of the event. Based on existing literature, this is the second record of the species in Brazilian waters. Analyzing meteorological and oceanographic features from the days preceding the record, it was not possible to make any association between the entanglement and the variables analyzed, and no explanatory driver could therefore be established for this unusual event. [ABSTRACT FROM AUTHOR]

Rough‐toothed dolphins (Steno bredanensis) typically inhabit deep oceanic waters from tropical to temperate waters worldwide. However, their ecology and behavior remain poorly understood. We investigated site fidelity and social structure of rough‐toothed dolphins using photo‐identification data collected between 2014 and 2022 in the continental shelf waters of the southwestern coast of Mexico. A total of 133 groups of rough‐toothed dolphins were recorded. Mean group size was 4.9 individuals (SD = 4.5), and dolphins were encountered in waters of a mean depth of 110 m (SD = 188). Of 228 individuals identified, 55% were observed once, 39% were seen between two and four times, and 6% were seen five times or more. Site fidelity analysis suggests three levels of site fidelity: transients, occasional visitors, and regular visitors, which are likely to affect the social structure. Through network analysis, nonrandom social patterns were identified (S = 1.25 ± 0.26) and dolphins exhibited both preferences and avoidances of social partners. Cluster analysis suggested significant divisions within the population (Q = 0.43 ± 0.05). Despite limitations related to sample size and design, this preliminary study suggests that rough‐toothed dolphins are best characterized by a fission‐fusion society, which is similar to most coastal delphinid populations. [ABSTRACT FROM AUTHOR]

Delphinidae is the most diverse family within the toothed whale clade, displaying two biosonar modes, different feeding strategies, and diving and habitat adaptations. This work examines the delphinid mandible to determine the association between shape, size and ecological variables in extant species. Geometric morphometric analysis on 95 mandibles belonging to 30 (out of 38) extant species, representatives of all 17 extant genera, was performed in occlusal (or dorsal) and lateral (or labial) view. The results reveal that feeding mode and climate primarily drive mandibular shape in extant species. Biosonar mode is an evolutionary driver in mandibular shape in occlusal view, while diet and maximum prey size play a significant role in size only in both views. By contrast, Diving Ecology, Superficial Temperature and Rostral index do not play a significant role in driving delphinid mandibular shape and size. [ABSTRACT FROM AUTHOR]

Cetaceans of the family Delphinidae are widely distributed throughout the global ocean, and it has been suggested that females exhibit philopatry. However, the duration of time that a maternal group of these highly mobile creatures spends inhabiting a particular region remains unknown. The objective of this study is to examine the genetic diversity of delphinids in the past and to shed light on the above question. In this study, we amplified and sequenced the mitochondrial DNA D-loop region from the skeletal remains of delphinids that were excavated from the Shomyoji Midden, a site situated on the western coast of Tokyo Bay and dating to 5000–3000 years before the present. We acquired prehistoric D-loop sequences of seven bottlenose dolphins, six Pacific white-sided dolphins, and a false killer whale. Notably, one or more haplotypes from the prehistoric individuals were detected in the geographically proximate modern conspecific populations across all three species. Whilst the genetic diversity of prehistoric and modern Pacific white-sided dolphin populations appears to be comparable, the modern bottlenose dolphin population demonstrates significantly lower genetic diversity when compared to its prehistoric counterpart in the vicinity of Tokyo Bay. The maternal groups of these species are speculated to have persisted in the same habitat for at least 4000 years. [ABSTRACT FROM AUTHOR]

Lobomycosis, also called paracoccidioidomycosis ceti, is a chronic mycotic cutaneous disease affecting odontocetes. Lobomycosis-like disease (LLD) has a clinical presentation consistent with lobomycosis but lacks a histological and molecular diagnosis. We review the literature on lobomycosis aetiology, clinical signs and pathogenesis, species affected and geographic distribution and examine the factors influencing the presence, transmission and prevalence of the disease, to better understand its ecology. In addition, we provide unpublished information on LLD in two common bottlenose dolphin (Tursiops truncatus) communities inhabiting the Gulf of Guayaquil, Ecuador. Lobomycosis and LLD occur in Delphinidae from the Atlantic, Pacific, and Indian Oceans between 33°N and 35°S. Primary risk factors include habitat, sex, age, sociality, and pollution. In dolphins from the Americas and Japan, lobomycosis is caused by Paracoccidioides ceti , family Ajellomycetaceae. The disease is characterized by cutaneous granulomatous lesions that may occur anywhere on the body, grow to large size, and may ulcerate. Histologically, the lesions consist of acanthosis and histiocytic granulomas between the skin and subcutaneous tissues, with inflammatory changes that extend deep into the dermis. Multiple yeast cells with a double refringent layer stained positive using Gomori-Grocott methenamine silver in the dermis of a T. truncatus from Ecuador diagnosed with LLD since 2011, a first record for the Southeast Pacific. Injuries may enable the entry of P. ceti into the dermis while skin contact likely favours transmission, putting males at higher risk than females. Lobomycosis and LLD may have a negative impact on small communities already threatened by anthropogenic factors. [ABSTRACT FROM AUTHOR]

Contamination by metals poses a significant threat to marine ecosystems and the health of marine organisms, including cetaceans. This study aimed to assess the concentrations of some metal and metalloids in the skin of bottlenose dolphins (Tursiops truncatus) from the Yucatan Peninsula in Mexico using Flame Atomic Absorption (FAA) spectrometry. A total of 41 skin samples were collected, comprising 22 samples from Yucatán in the Gulf of Mexico and 19 samples from Chetumal Bay in the Caribbean. The results of our analysis revealed the presence of various elements in the skin of bottlenose dolphins from coastal waters in the Yucatan Peninsula. Among the detected metals, zinc (Zn), iron (Fe), and arsenic (As) exhibited notable concentrations, with the order of abundance being Zn > Fe > As > Cu > Cr > Cd > Ni. The elevated concentrations of Zn and Fe suggest potential exposure and accumulation of these metals in the studied dolphin population. Interestingly, measurable concentrations of lead (Pb) and manganese (Mn) were not detected in the skin samples, indicating either low levels or the absence of their accumulation in the studied dolphin populations. The absence of measurable Pb concentrations is particularly encouraging as Pb is known to have detrimental effects on marine organisms and is commonly associated with anthropogenic activities. This study provides valuable insights into the metal contamination status in bottlenose dolphins from the Yucatan Peninsula, Mexico. The notable concentrations of Zn, Fe, and As raise concerns about potential health risks to these charismatic marine mammals. Further research is warranted to investigate the sources and pathways of heavy metal exposure in this population and to understand the potential consequences of such exposure on the health and well-being of bottlenose dolphins in the Yucatan Peninsula. [ABSTRACT FROM AUTHOR]

This article provides information on the karyotype of the tucuxi, a freshwater dolphin species found in the Amazon River basin. The study found that all tucuxi specimens had a diploid number of 44 and a specific karyotype formula. The document also includes references to other scientific articles that discuss the karyotypes of different cetacean species, as well as other mammalian species. These articles provide valuable information for researchers studying the genetics and evolution of these animals. [Extracted from the article]

Introduction: The amygdala is a noticeable bilateral structure in the medial temporal lobe and it is composed of at least 13 different nuclei and cortical areas, subdivided into the deep nuclei, the superficial nuclei, and the remaining nuclei which contain the central nucleus (CeA). CeA mediates the behavioral and physiological responses associated with fear and anxiety through pituitary-adrenal responses by modulating the liberation of the hypothalamic Corticotropin Releasing Factor/Hormone. Methods: Five dolphins of three different species, belonging to the family Delphinidae (three striped dolphins, one common dolphin, and one Atlantic spotted dolphin), were used for this study. For a precise overview of the CeA's structure, thionine staining and the immunoperoxidase method using calbindin D-28k were employed. Results: CeA extended mainly dorsal to the lateral nucleus and ventral to the striatum. It was medial to the internal capsule and lateral to the optic tract and the medial nucleus of the amygdala. Discussion: The dolphin amygdaloid complex resembles that of primates, including the subdivision, volume, and location of the CeA. [ABSTRACT FROM AUTHOR]

A review of the prey of three amphiatlantic dolphin species, Tursiops truncatus, Stenella coeruleoalba and Delphinus delphis, is carried out. The main objective of this work is to review the feeding of these species in the Atlantic in order to assess the degrees of trophic competition and speciation pressure. A total of 103 fish families, 22 cephalopod families and 19 crustacean families have been counted, from which the species identified to the genus level only included seventy-one fish, twenty cephalopods and five crustaceans, and the total species identified included three-hundred-one fish, fifty cephalopods and twenty-six crustaceans. The most consumed prey were fish, followed by cephalopods and crustaceans. The exclusive prey consumed by each of the three dolphin species, as well as those shared by all or at least two of them, have also been counted. T. truncatus is the most general; however, the western Atlantic populations exhibit high dietary specialization compared to the eastern Atlantic populations, reflecting strong speciation pressure on both sides of the Atlantic. D. delphis and S. coeruleoalba, despite their amphiatlantism, have hardly been studied in the western Atlantic, except for a few references in the southern hemisphere, so the fundamental differences between the two species and their comparison with T. truncatus have been established with records from the eastern Atlantic. All three dolphin species have been observed to be expanding, especially D. delphis. This northward expansion and that of their prey is discussed. [ABSTRACT FROM AUTHOR]

The white-beaked dolphin (Lagenorhynchus albirostris) is the second most frequently stranded cetacean species along the Danish coastline. The northern North Sea, the Skagerrak, the Kattegat and the Danish straits are part of the species distributional range. Here, we present eight incidents of breeding activity for the white-beaked dolphin in the inner Danish waters, reviewed from yearly reports made by the National Contingency Plan concerning strandings of marine mammals in Denmark from 2009 to 2023, Danish Wildlife Diseases Surveillance reports from 2014 to 2023 and the citizen science database Naturbasen in the period 2002 to 2023. Three pregnant females, three lactating females and one calf were found stranded in the inner Danish waters. Besides this, there have been live sightings of a female with a newborn calf. We conclude that the white-beaked dolphin is breeding in the inner Danish waters. [ABSTRACT FROM AUTHOR]

The white-beaked dolphin (Lagenorhynchus albirostris) is the second most frequently stranded cetacean species along the Danish coastline. The northern North Sea, the Skagerrak, the Kattegat and the Danish straits are part of the species distributional range. Here, we present eight incidents of breeding activity for the white-beaked dolphin in the inner Danish waters, reviewed from yearly reports made by the National Contingency Plan concerning strandings of marine mammals in Denmark from 2009 to 2023, Danish Wildlife Diseases Surveillance reports from 2014 to 2023 and the citizen science database Naturbasen in the period 2002 to 2023. Three pregnant females, three lactating females and one calf were found stranded in the inner Danish waters. Besides this, there have been live sightings of a female with a newborn calf. We conclude that the white-beaked dolphin is breeding in the inner Danish waters.

The coexistence of sympatric species with similar ecological requirements involves niche partitioning via interspecific differences in resource use and behaviour. Behavioural patterns of coexisting species can also be indicative of the functions of interspecific interactions, including those between species that form mixed-species groups. Here, we used Markov chain analysis applied to behavioural focal follow data of Australian humpback, Sousa sahulensis (hereafter 'humpback dolphins') and Indo-Pacific bottlenose dolphins, Tursiops aduncus (hereafter 'bottlenose dolphins') observed around the North West Cape, Western Australia, to investigate potential behavioural coexistence mechanisms and the functions of their mixed-species groups. During six austral winter (April to October) field seasons (2013–2015, 2018–2019 and 2021), we recorded 560 dolphin sightings from which we obtained 562 sequences of behavioural transitions: 222 humpback dolphin single-species sequences, 262 bottlenose dolphin single-species sequences and 78 mixed-species sequences. Humpback dolphins spent more time travelling in addition to having higher transition probabilities towards travelling and longer bout lengths of travelling, while bottlenose dolphins spent more time foraging and had longer foraging bouts. These behavioural patterns indicate that humpback and bottlenose dolphins differ in their use of the study area. In particular, they suggest interspecific temporal differences in foraging behaviour, which may facilitate coexistence. When in mixed-species groups, humpback and bottlenose dolphins altered their behavioural patterns by exhibiting higher transition probabilities towards socializing and increasing time spent socializing, suggesting that their mixed-species groups may have a social function. Overall, our results indicate that behavioural differences may play an important role in facilitating the coexistence of sympatric delphinids and that social benefits may be a key driver of the formation of mixed-species groups. • Behaviour indicates coexistence mechanisms and functions of mixed-species groups. • We used Markov chain analysis of humpback and bottlenose dolphin focal follow data. • We compared behavioural transitions, bout lengths, budgets and cumulative budgets. • Temporal differences in foraging reduce competition and facilitate coexistence. • Increased socializing in mixed-species groups supports social advantage hypothesis. [ABSTRACT FROM AUTHOR]

This study reveals early prey eating by a short‐finned pilot whale (Globicephala macrorhynchus Gray, 1846, Cetacea: Delphinidae) in the Canary Islands. Stomach contents, trophic markers, skin isotopic ratios of nitrogen (δ15N:15N/14N) and carbon (δ13C:13C/12C), and fatty acid profiles of the blubber of a short‐finned pilot whale of 213 cm size euthanized in free‐ranging conditions were analyzed. A total of 15 species of oegopsid squids, mostly diel vertical mesopelagic migrant species of the families Enoploteuthidae, Ommastrephidae, and Histioteuthidae, as well as mother's milk, were identified in the stomach contents. Asperoteuthis acanthoderma (Lu, 1977, Cephalopoda: Chiroteuthidae) was found as first time in this area, suggesting the possibility of its presence on both sides of the subtropical Atlantic, extending its current known distribution. The δ15N value (11.55‰) was higher than expected based on the size range of squid ingested, but lower than that of adult pilot whales, suggesting that mother's milk intake has a significant effect on these values in calves. Similarly, the δ13C values (−17.99‰) were shifted to those of adult pilot whales rather than the ingested squids, also due to the ingestion of high‐fat breast milk. The fatty acid (FA) composition of blubber showed a clear stratification. Long‐chain polyunsaturated fatty acids (LC‐PUFA) were mainly present in the inner layer, while most relevant ≤C20 monounsaturated fatty acids (MUFA) were more abundant in the outer layer. [ABSTRACT FROM AUTHOR]

Context: Strandings are an important source of information for estimating marine mammal biodiversity, particularly in data-sparse ocean basins such as Oceania. Aims: Here, we report on knowledge acquired from 218 stranding events recorded in the waters of New Caledonia (1877–2022). Methods: We investigated spatio-temporal distribution, stable isotope signatures, trace element concentrations, biometry measurements, genetic diversity, and diet, for the four most commonly stranded taxa (dugongs, 35% of events; sperm whales, 19%; Delphinidae, 18%; pygmy and dwarf sperm whales, 14%). Key results: Beginning in 1991, reports of stranding events increased (183 events, 322 individuals, 20 species from seven families: Dugongidae, Physeteridae, Delphinidae, Kogiidae, Ziphiidae, Balaenopteridae, Otariidae), with hotspots identified on the west coast (Bourail, Ouano, Nouméa) and in Prony Bay. Causes of death were not determined in 84% of stranding events, but were identified in the majority of expert-led necropsies (24 of 29 individuals from 10 species). Yet, valuable information regarding the impact of anthropogenic activities was gathered for some species of concern, such as the endangered dugong (28% human-caused). Since 2016, training and outreach have been provided to rangers, veterinarians, and various public safety officers to support their engagement in the scientific monitoring of marine mammal strandings. A website (www.rescue.ird.nc) was developed to facilitate standardised data collection and storage, and to provide public access to stranding records. Conclusion: Although the number of individuals reported here remains modest, this study provides new information on poorly documented species in New Caledonia. Implications: Long-term monitoring of strandings can help design effective conservation measures. RESUME: Contexte: Les échouages constituent une source d'informations importante pour estimer la biodiversité des mammifères marins, en particulier dans les bassins océaniques pour lesquels les données sont rares, comme l'Océanie Objectif: Nous présentons ici les connaissances acquises à partir de 218 échouages enregistrés dans les eaux de Nouvelle-Calédonie (1877–2022). Méthodes: Nous avons étudié la distribution spatio-temporelle, les signatures isotopiques, les éléments traces, les mesures biométriques, la diversité génétique et le régime alimentaire des quatre taxons les plus fréquemment échoués (dugongs, 35% des échouages; cachalots, 19%; Delphinidae, 18% ; cachalots pygmées et nains, 14%). Principaux résultats: À partir de 1991, les signalements d'échouages ont augmenté (183 événements, 322 individus, 20 espèces de sept familles: Dugongidae, Physeteridae, Delphinidae, Kogiidae, Ziphiidae, Balaenopteridae, Otariidae), avec des points chauds identifiés sur la côte ouest de la Grande Terre (Bourail, Ouano, Nouméa) et dans la Baie de Prony. Les causes de décès n'ont pas été déterminées pour 84% des échouages, mais elles ont été identifiées dans la majorité des autopsies réalisées par des vétérinaires (24 des 29 individus de 10 espèces). Des informations précieuses concernant l'impact des activités anthropiques ont été recueillies pour certaines espèces préoccupantes, telles que le dugong, une espèce en voie de disparition (28% des échouages d'origine humaine). Depuis 2016, des formations et des activités de sensibilisation ont été dispensées aux gardes nature, aux vétérinaires et à divers agents publics pour soutenir leur engagement dans la surveillance scientifique des échouages de mammifères marins. Un site Web (www.rescue.ird.nc) a été développé pour faciliter la collecte et le stockage de données standardisées et pour fournir un accès public aux enregistrements d'échouages. Conclusion: Bien que le nombre d'individus signalés échoués ici reste modeste, cette étude apporte de nouvelles informations sur des espèces peu documentées en Nouvelle-Calédonie. Implications: La surveillance à long terme des échouages peut aider à concevoir des mesures de conservation efficaces. Map of strandings in New Caledonia; people gathered around a stranded whale; four commonly stranded species. Conservation of marine mammals in Oceania is limited by a lack of understanding of these relatively rare, yet emblematic species. Here, we report on significant biological and ecological data acquired from several decades of monitoring strandings in New Caledonia. This increased knowledge may help guide management measures locally and regionally. Photograph by Marine Mammal Stranding Center. This article belongs to the Collection Marine Mammals in the Pacific. [ABSTRACT FROM AUTHOR]

Toothed cetaceans represent a diverse and important component in poorly studied pelagic food webs. We used the variation in δ13C and δ15N values in tooth dentin and bone collagen sampled from 185 specimens of 23 species (families Delphinidae, Physeteridae, Kogiidae, Phocoenidae, and Ziphiidae) stranded in the western South Atlantic Ocean (WSAO) to estimate the isotopic niche width and assess the interspecific isotopic niche overlap. Two gradients of increasing δ13C values among species were evidenced: ocean-coast and high-to-low latitudes. Variation in δ13C and δ15N values indicated the existence of at least four trophic and habitat-related guilds: neritic high trophic-level predators (Pseudorca crassidens, Tursiops truncatus gephyreus, T. truncatus truncatus and Phocoena spinnipinis); oceanic intermediate trophic-level predators (Orcinus orca, Steno bredanensis, Kogia breviceps, Lagenodelphis hosei, Physeter macrocephalus, Delphinus delphis and Stenella frontalis), oceanic low trophic-level predators (Grampus griseus, P. crassidens—mass stranded group, Mesoplodon grayi, M. densirostris, Ziphius cavirostris, Globicephala melas, S. coeruleoalba, and K. sima), all from the subtropics, and a temperate/polar grouping of neritic/oceanic low trophic-level predators (Berardius arnuxii, M. layardii, M. hectori and P. dioptrica). Furthermore, our results also suggest the occurrence of putative ecotypes of O. orca and P. crassidens. The isotopic niche width was highly variable among species, with high niche overlap among several oceanic taxa. The results of the present study suggest a wide variation in trophic position, habitat and, therefore, the ecological role of different odontocete species in the WSAO ecosystems. [ABSTRACT FROM AUTHOR]