Anthropogenic contaminants in the marine environment often biodegrade slowly, bioaccumulate in organisms, and can cause reproductive, immune, and developmental effects on wildlife; however, their effects on cetacean health and behavior have not been extensively studied. This study aims to expand knowledge concerning concentrations and biological effects of endocrine disrupting contaminants and essential and non-essential inorganic elements in stranded cetaceans. We evaluated tissue samples and pathology data from 66 odontocetes that stranded in the southeastern United States during 2012– 2017. Using mass spectrometry blubber samples were analyzed for five endocrine disrupting contaminants (atrazine, bisphenol-A, diethyl phthalate, nonylphenol ethoxylate, triclosan), and liver samples were analyzed for 12 inorganic elements (As, Cd, Co, Cu, Mg, Mn, Fe, Pb, Hg, Se, Tl, Zn). Results from this study demonstrate that exposure to certain contaminants may be associated with subtle or sublethal cellular changes in free-ranging marine mammals that could contribute to health declines or stranding. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Every year hundreds of cetaceans strand on New Zealand beaches. Options for dealing with disposal of their carcasses are few, creating significant problems for the Department of Conservation (DOC). More often than not their carcasses are buried in beaches at or just above high water mark, near where the animals have stranded. The primary objective of this thesis is to determine the effects of cetacean burial on beach sediments, and evaluate potential health and safety risks associated with this practice. A secondary objective of this thesis is to appraise the appropriateness of one location DOC has repeatedly transported cetacean carcasses to and buried within beach sediments, Motutapu Island in Waitemata Harbour. The chemical effects of cetacean burial over a six-month period are reported for two sites at which animals were buried in 2008, Muriwai and Pakiri beaches; the biological effects of this burial are reported for one of these sites, Muriwai Beach, 12 months post burial. Intertidal faunal and floral inventories are provided for six sites around Motutapu Island, and these then compared and contrasted with inventories compiled from an additional 290 intertidal sites between Whangarei Heads and Tauranga Harbour, North Island East Coast, to appraise the relative uniqueness of intertidal species diversity around Motutapu Island. At both Muriwai and Pakiri beaches, nitrogen and phosphate concentrations in surface sands changed considerably following cetacean burial, although over six months the effect was localized and elevated concentrations of these two chemicals that could be attributed to a buried carcass did not extend more than 40 m from the site of whale burial. Deep-core profiles revealed nitrogen and phosphate concentrations at and in the immediate vicinity of cetacean burial approximately six months after burial to be markedly elevated to the level of the water table, but elevated concentrations attributable to the buried carcass were not observed greater than 25 m from the site of burial. Elevated concentrations of nitrogen and phosphates in beaches persist in surface sediments for at least six months post burial. Twelve months post cetacean burial no significant difference in species richness or abundance were apparent in intertidal communities extending along transects proximal to and some distance from the Muriwai Beach carcass; there is no evidence for any significant short-term (to 12 months) biological effects of cetacean burial in beaches. Of those shores on Motutapu Island accessible by earth-moving equipment and large vessels capable of dealing with and transporting large cetacean carcasses, Station Bay appeared to be the most appropriate site for whale burial. However its small size and relatively high biological value (fairly high species richness for comparable shores between Whangarei Heads and Tauranga) renders it an inappropriate long-term option for whale burial. Other shores on Motutapu Island host some of the highest species richness of all shores surveyed between Whangarei Heads and Tauranga Harbour, rendering them entirely inappropriate locations for burying cetaceans, over and above other variables that may influence disposal location identification (such as archaeological sites, dwellings and accessibility). Motutapu Island is not considered an appropriate location for cetacean burial within beaches. Alternative disposal strategies need to be explored for dealing with cetaceans that strand on Auckland east coast beaches. Although burial is the most convenient and most economical strategy to dispose of cetacean carcass, especially in mass stranding events or when cetaceans are of large size, and the biological effects of this practice are not considered significant (for the one whale that could be studied), persistent enrichment of beach sediments with organic matter could result in prolonged persistence of pathogens in beaches, causing unforeseen risks to human health and safety. Recommendations are made to minimize possible threats to public following burial of cetaceans in beaches, until the potential health risks of burial are more fully understood.

Social organization of dolphins in extensive societies has not been well studied. Off Kaikoura, New Zealand, thousands of dusky dolphins (Lagenorhynchus obscurus) gather, feeding nocturnally on deep scattering layer prey, resting and socializing diurnally. During 1997-2003, interval sampling was used to monitor large assemblages numbering hundreds (n=169), smaller mating groups (mean+s.e.=7+1.6 adults, n=42), mother-calf nurseries (mean+s.e.=13+1.6 adults, 1+0.5 juveniles, 4+0.7 calves and 1+0.4 neonates, n=41), and non-mating adult groups (mean+s.e.= 9+1.3 adults, 1+0.2 juvenile, n=37). Group size, distance from shore (east), ranging along shore (north), traveling, inter-individual distance, and noisy leaping peaked in winter (n=39), with dolphins maintaining closer proximity to each other in smaller, more restful groups, closer to shore during the spring-summer-autumn (n=234) reproductive seasons. Dolphin groups were found closest to shore (west) during early morning, spread out and leaping often. Resting peaked at midday in tight groups. Late in the day, dolphins spread out, moving eastward (offshore) in preparation for feeding. Large groups exhibited coordinated travel, with noisy leaps as a directional signal. "Mating of the quickest" occurred in groups of (median) 6 males chasing 1 female. Leaping rarely occurred in restful nurseries, which at times associated with Hector's dolphins (Cephalorhynchus hectori). Other mixed-species groups included common dolphins (Delphinus delphis), southern right whale dolphins (Lissodelphis peronii), long-finned pilot whales (Globicephala malaena), and bottlenose dolphins (Tursiops truncatus). Killer whales (Orcinus orca) elicited predator assessment and evasion. Whale riding occurred with larger whales. Residence was seasonal, with 1,969+814.9 from a population of 12,626 dolphins spending 103+38.0 days in Kaikoura (mean+s.e., mark-recapture mortality, single-season lagged-ID emigration models, n=153 weeks). Dolphins (n=39) summering in Kaikoura migrated to the Marlborough Sounds in winter, where small, coordinated groups foraged diurnally on schooling fishes in shallow bays, often associated with sea birds and New Zealand fur seals (Arctocephalus forsteri). Aquaculture may threaten dusky dolphin foraging habitat in Admiralty Bay, where an estimated 220 dolphins gathered to feed each winter. Photo-identification research, enhanced by digital techniques, demonstrated a structured fission-fusion society. Dusky dolphins associated with preferred long-term (>1,000 days) hunting companions in Admiralty Bay and non-random casual acquaintances (200 days) in Kaikoura (lagged-association models).

<p>Passive acoustic monitoring is being used more frequently to examine the occurrence, distribution, and habitat use of cetaceans. Long-term recordings from passive acoustic recorders allow the examination of diel, seasonal, and inter-annual variation in the occurrence of vocalizing marine mammals. With the increased use of passive acoustics as a tool for studying marine mammals, the ability to classify calls to the species level is becoming more important. While studies have found distinctive vocalizations in some cetacean species, further work is required in order to differentiate the vocalizations of delphinid species. I sought to classify odontocete vocalizations to species and to describe temporal variation and depth-related differences in the occurrence of cetacean vocal events detected in archival passive acoustic recordings in Onslow Bay, North Carolina. To determine if odontocete species in offshore waters of North Carolina could be distinguished by their whistles and clicks, I used a towed hydrophone array to make acoustic recordings of species encountered during concurrent visual and acoustic surveys between 2007 and 2010. I recorded whistles from four species (Atlantic spotted dolphins, bottlenose dolphins, rough-toothed dolphins, and short-finned pilot whales) and clicks from five species (Risso's dolphins in addition to the four species listed above). After running a classification and regression tree (CART) analysis on 22 measured variables from the contours of four species' whistles, I generated an optimal classification tree that had a correct classification rate of 74.2%. My results indicate that species-specificity exists in the four species' whistles. My examination of the spectral structure of clicks showed that only Risso's dolphins produced clicks with distinctive spectral banding patterns, although I found that other click parameters, particularly peak and center frequency, might be useful in differentiating the other species. I then used the distinctive banding pattern that I observed in Risso's dolphin clicks to identify this species in recordings made by archival passive acoustic recorders that were deployed at various times and locations between 2007 and 2010. I used these recordings to determine how vocal events varied temporally and spatially in Onslow Bay. My analysis of vocal events observed in these recordings showed that Risso's dolphins, sperm whales, and other delphinids are present in Onslow Bay throughout the year; Kogia spp. occur sporadically; and fin and minke whales produce calls that can be detected only between late fall and early spring. I also detected low-frequency downsweeps and two types of low-frequency pulse trains produced by unknown species. After looking at the occurrence of fin whale 20-Hz pulses in relation to downsweeps, I suggest that the downsweeps are produced by sei whales due to the lack of overlap in occurrence. When I looked for diel patterns in the odontocete vocal events, I found a nocturnal increase in the occurrence of clicks from Risso's dolphins and sperm whales, but no diel variation in Kogia clicks. I also found that unidentified delphinids showed either an increase in click events at dawn or at night, depending on the time of year and recording location. Finally, my analysis of acoustic data from five recorders deployed in three different depth ranges revealed that there was greater unidentified delphinid and sperm whale vocal activity on recorders located in deep waters, suggesting a greater diversity and density of animals in deeper waters of Onslow Bay. Together, the results of my dissertation demonstrate the value of passive acoustic monitoring in understanding the distribution and temporal trends in cetacean occurrence, and highlight the importance of classifying sounds to the species level in order to better understand the temporal and spatial patterns found.</p> / Dissertation

Social organization of dolphins in extensive societies has not been well studied. Off Kaikoura, New Zealand, thousands of dusky dolphins (Lagenorhynchus obscurus) gather, feeding nocturnally on deep scattering layer prey, resting and socializing diurnally. During 1997-2003, interval sampling was used to monitor large assemblages numbering hundreds (n=169), smaller mating groups (mean+s.e.=7+1.6 adults, n=42), mother-calf nurseries (mean+s.e.=13+1.6 adults, 1+0.5 juveniles, 4+0.7 calves and 1+0.4 neonates, n=41), and non-mating adult groups (mean+s.e.= 9+1.3 adults, 1+0.2 juvenile, n=37). Group size, distance from shore (east), ranging along shore (north), traveling, inter-individual distance, and noisy leaping peaked in winter (n=39), with dolphins maintaining closer proximity to each other in smaller, more restful groups, closer to shore during the spring-summer-autumn (n=234) reproductive seasons. Dolphin groups were found closest to shore (west) during early morning, spread out and leaping often. Resting peaked at midday in tight groups. Late in the day, dolphins spread out, moving eastward (offshore) in preparation for feeding. Large groups exhibited coordinated travel, with noisy leaps as a directional signal. "Mating of the quickest" occurred in groups of (median) 6 males chasing 1 female. Leaping rarely occurred in restful nurseries, which at times associated with Hector's dolphins (Cephalorhynchus hectori). Other mixed-species groups included common dolphins (Delphinus delphis), southern right whale dolphins (Lissodelphis peronii), long-finned pilot whales (Globicephala malaena), and bottlenose dolphins (Tursiops truncatus). Killer whales (Orcinus orca) elicited predator assessment and evasion. Whale riding occurred with larger whales. Residence was seasonal, with 1,969+814.9 from a population of 12,626 dolphins spending 103+38.0 days in Kaikoura (mean+s.e., mark-recapture mortality, single-season lagged-ID emigration models, n=153 weeks). Dolphins (n=39) summering in Kaikoura migrated to the Marlborough Sounds in winter, where small, coordinated groups foraged diurnally on schooling fishes in shallow bays, often associated with sea birds and New Zealand fur seals (Arctocephalus forsteri). Aquaculture may threaten dusky dolphin foraging habitat in Admiralty Bay, where an estimated 220 dolphins gathered to feed each winter. Photo-identification research, enhanced by digital techniques, demonstrated a structured fission-fusion society. Dusky dolphins associated with preferred long-term (>1,000 days) hunting companions in Admiralty Bay and non-random casual acquaintances (200 days) in Kaikoura (lagged-association models).

Every year hundreds of cetaceans strand on New Zealand beaches. Options for dealing with disposal of their carcasses are few, creating significant problems for the Department of Conservation (DOC). More often than not their carcasses are buried in beaches at or just above high water mark, near where the animals have stranded. The primary objective of this thesis is to determine the effects of cetacean burial on beach sediments, and evaluate potential health and safety risks associated with this practice. A secondary objective of this thesis is to appraise the appropriateness of one location DOC has repeatedly transported cetacean carcasses to and buried within beach sediments, Motutapu Island in Waitemata Harbour. The chemical effects of cetacean burial over a six-month period are reported for two sites at which animals were buried in 2008, Muriwai and Pakiri beaches; the biological effects of this burial are reported for one of these sites, Muriwai Beach, 12 months post burial. Intertidal faunal and floral inventories are provided for six sites around Motutapu Island, and these then compared and contrasted with inventories compiled from an additional 290 intertidal sites between Whangarei Heads and Tauranga Harbour, North Island East Coast, to appraise the relative uniqueness of intertidal species diversity around Motutapu Island. At both Muriwai and Pakiri beaches, nitrogen and phosphate concentrations in surface sands changed considerably following cetacean burial, although over six months the effect was localized and elevated concentrations of these two chemicals that could be attributed to a buried carcass did not extend more than 40 m from the site of whale burial. Deep-core profiles revealed nitrogen and phosphate concentrations at and in the immediate vicinity of cetacean burial approximately six months after burial to be markedly elevated to the level of the water table, but elevated concentrations attributable to the buried carcass were not observed greater than 25 m from the site of burial. Elevated concentrations of nitrogen and phosphates in beaches persist in surface sediments for at least six months post burial. Twelve months post cetacean burial no significant difference in species richness or abundance were apparent in intertidal communities extending along transects proximal to and some distance from the Muriwai Beach carcass; there is no evidence for any significant short-term (to 12 months) biological effects of cetacean burial in beaches. Of those shores on Motutapu Island accessible by earth-moving equipment and large vessels capable of dealing with and transporting large cetacean carcasses, Station Bay appeared to be the most appropriate site for whale burial. However its small size and relatively high biological value (fairly high species richness for comparable shores between Whangarei Heads and Tauranga) renders it an inappropriate long-term option for whale burial. Other shores on Motutapu Island host some of the highest species richness of all shores surveyed between Whangarei Heads and Tauranga Harbour, rendering them entirely inappropriate locations for burying cetaceans, over and above other variables that may influence disposal location identification (such as archaeological sites, dwellings and accessibility). Motutapu Island is not considered an appropriate location for cetacean burial within beaches. Alternative disposal strategies need to be explored for dealing with cetaceans that strand on Auckland east coast beaches. Although burial is the most convenient and most economical strategy to dispose of cetacean carcass, especially in mass stranding events or when cetaceans are of large size, and the biological effects of this practice are not considered significant (for the one whale that could be studied), persistent enrichment of beach sediments with organic matter could result in prolonged persistence of pathogens in beaches, causing unforeseen risks to human health and safety. Recommendations are made to minimize possible threats to public following burial of cetaceans in beaches, until the potential health risks of burial are more fully understood.

Among vertebrates, whole-body movement is centered around the vertebral column. The bony vertebral column primarily consists of trabecular (spongy) bone that adapts in vivo to support mechanical demands respective to region, ontogeny, ecology, and locomotion. Previous work has extensively investigated the formfunction relationships of vertebral trabecular bone in terrestrial mammals, who use limb contact with a substrate as the primary support against gravity. However, we lack data from obligate swimming mammals whose locomotor ecology diverged from their terrestrial counterparts in two major ways: (1) body mass is supported by water’s uplifting buoyant forces and (2) swimmers power movement through dorsoventral loading of the axial body. This study examined vertebral trabecular bone mechanical properties and micoarchitecture from fully aquatic mammals, specifically sirenians (i.e. manatees) and cetaceans (i.e. dolphins and whales). We compression tested bone from several regions of the vertebral column among developmental stages in Florida manatees (Trichechus manatus latirostris) and among 10 cetacean species (Families Delphinidae and Kogiidae) with various swimming modes and diving behaviors. In addition, we microCT scanned a subset of cetacean vertebrae before subjecting them to mechanical tests. We demonstrated that in precocial manatee calves, vertebrae were the strongest and toughest in the posterior vertebral column, which may support rostrocaudal force propagation and increasing bending amplitudes towards the tail tip during undulatory swimming. Among cetaceans, we showed that greatest strength, stiffness, toughness, bone volume fraction, and degree of anisotropy were in rigidtorso shallow-divers, while properties had the smallest values in flexible-torso deep-divers. We propose that animals swimming in shallower waters actively swim more than species that conduct habitual glides during deep descents in the water column, and place comparatively greater loads on their vertebral columns. We found that cetacean bone volume fraction was the best predictor for mechanical properties. Due to the shared non-weight bearing conditions of water and microgravity, we present these data as a contribution to the body of work investigating bone adaptations in mammals that live in weightless conditions throughout life and evolutionary history. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Dans le cadre de nombreuses règlementations, l’établissement de stratégies de suivi des populations de cétacés est devenu un besoin prioritaire. Les principales caractéristiques d’une stratégie de suivi sont la signification écologique, la crédibilité statistique et le rapport qualité/coût élevé. La mise en place d’indicateurs permet de réduire les coûts de suivi, et propose un outil de communication entre scientifiques et gestionnaires. Un indicateur est une donnée vérifiable et mesurable qui renseigne sur plus qu’elle-même. La collecte des données d’échouages est peu coûteuse, mais l’absence de stratégie d’échantillonnage des populations en mer est une entrave à leur utilisation dans le cadre de stratégies de suivi. L’objectif de cette thèse est de développer des indicateurs des populations de cétacés à partir des données d’échouages. Quatre indicateurs ont été développés au cours de cette thèse. La part des cétacés échoués par rapport aux cétacés morts en mer a été estimée. Les séries temporelles d’échouages ont été affranchies des conditions de dérive, par l’établissement de l’hypothèse nulle (hypothèse d’uniformité spatiale et temporelle des cétacés morts en mer) et constitue l’anomalie d’échouage. La cartographie de la mortalité de cétacés a été réalisée, et détermine le nombre de dauphins morts en mer, indépendamment de leur probabilité de s’échouer. Enfin la distribution de mortalité observée par rapport à la distribution attendue des cétacés morts sous l’hypothèse nulle a été calculée. Elle permet d’identifier des zones de fortes mortalité ou abondance relative. Ces quatre indicateurs pourront être intégrés à différents plans de gestion, nationaux ou internationaux. / Under national and international regulations, the establishment of cetacean population monitoring strategies became a priority. Monitoring main expected characteristics are the ecological significance, the statistical credibility and the cost-effectiveness. The use of indicators reduces monitoring cost, and constitutes communication tool between scientists and policy-makers. Indicators are measurable and verifiable data, which inform on more than themselves. The collect of stranding data is cost-efficient, but the lack of sampling strategy remains a hindrance to their use in context of monitoring strategy. The aim of this study is to develop cetacean population indicators based on stranding data.Four indicators were developed during this work. The proportion of stranded cetaceans compared to dead cetaceans at sea was estimated. Stranding long term time series were freed from drift conditions by the construction of the null hypothesis (that is a hypothesis of spatial and temporal uniformity of dead cetaceans). It constituted the stranding anomaly. The cetacean mortality cartography estimated the number of dead cetaceans at sea, independently of the stranding probability. Finally, cetacean mortality anomaly was calculated as the difference between mortality areas of stranded cetaceans and theoretical distribution of dead cetaceans predicted to strand under the null hypothesis. This anomaly identified high mortality or high relative abundance areas. These indicators could be integrated to many national and international management strategies.

In four chapters that this thesis consists of is presented the protection provided to cetaceans by international law. The first chapter gives insight into the biology of cetaceans, names facts relevant to their conservation and its legal basis. The second chapter deals with legal regulation of whaling. It analyzes the history and current situation in the International Whaling Commission as the only global organization to manage the exploitation of large cetaceans, particularly in terms of adopting protective measures for the recovery and conservation of whale stocks. The third chapter focuses on the species approach in protection of cetaceans as endangered animals. The fourth chapter addresses the protection of cetaceans' environment. First it deals with the protection of marine environment in general and then with the protection of cetacean habitats.

Aquatic mammals are sentinels of zoonotic pathogens that may be a threat to species conservation, to humans and domestic animals. Brucella genus is responsible for brucellosis, one of the main widespread zoonosis. In aquatic mammals, Brucella spp. was firstly described in 1994 and currently there are two recognized species infecting that group: B. ceti and B. pinnipedialis. In cetaceans, Brucella spp. has been linked to asymptomatic infection, acute or chronic disease and several pathological processes which may lead to stranding and/or death. In pinnipeds, pathogenicity of Brucella spp. is still unclear. Data about Brucella spp. in aquatic mammals in South Atlantic Ocean particularly in Brazil is limited, with a significant knowledge gap despite the rich diversity of this group. In this research, we investigated exposure to and/or infection by Brucella spp. by serological, molecular, histopathological, immunohistochemical and microbiological methods in samples of aquatic mammals of Brazil kept at the Marine Mammal Tissue Bank, Department of Pathology, School of Veterinary Medicine and Animal Sciences, University of São Paulo, Brazil. Sera from 63 cetaceans [families Iniidae (n=37), Delphinidae and Kogiidae (n=26)], 35 pinnipeds (Southern elephant Seals, Mirounga leonina), and 21 West Indian manatees (Trichechus manatus) were tested via the Rose Bengal Test, a commercial competitive enzyme-linked immunosorbent assay (c-ELISA) and the serum agglutination test (SAT; selected c-ELISA positives) to detect Brucella spp. antibodies. In addition, DNA from selected samples of 124 cetaceans, 4 pinnipeds and 1 manatee were analyzed by conventional PCR and/or real-time PCR (qPCR) targeting the genus Brucella spp. Culture, histopathology and immunohistochemistry (IHC) were performed in samples from exposed or infected individuals (serology and/or conventional PCR/qPCR positives; n=13). Antibodies against Brucella spp. were detected in 3/35 (8.6%) of the M. leonina tested while Iniidae and Kogiidae cetaceans and manatees were negative. Brucella spp. DNA was detected in 4/124 (3.2%) of the cetaceans tested by conventional PCR/qPCR: one Clymene dolphin (Stenella clymene) with acute brucellosis, positive by serology and IHC; and three other individuals without available sera: one asymptomatic Franciscana (Pontoporia blainvillei), positive by qPCR and IHC; one case of chronic brucellosis in a Spinner dolphin (Stenella longirostris) presenting fibrinosuppurative atlanto-occipital osteoarthritis with abscess formation, positive by qPCR and by IHC; one Guiana dolphin (Sotalia guianensis), positive by conventional PCR/qPCR and by IHC and previously diagnosed with cetacean morbillivirus. Despite negative PCR amplification, Brucella-type lesions were found in one S. clymene and one pigmy killer whale (Feresa attenuata), both positive by serology and by IHC. Positive serology and/or IHC suggested exposure and/or Brucella-infection in three short-finned pilot whale (Globicephala macrorhynchus), two melon-headed whale (Peponocephala electra), a bottlenose dolphin (Tursiops truncatus) and a S. clymene. Main part of the Brucella spp. exposed or infected cetaceans came from State of Ceará, Northeastern Brazil. Culture was not successful, hampering strains classification. All the pinnipeds and the manatees tested by PCR were negative. Opportunistic screening of Leptospira spp. exposure via the microscopic agglutination test on all sera samples used for the Brucella spp. screening gave negative results. In conclusion, we found Brucella spp. exposure, asymptomatic infection, as well as cases of acute and chronic brucellosis and coinfection by Brucella spp. and other pathogens. To our knowledge, this research is the first long-term survey of Brucella spp. in aquatic mammals in South America, widening the hosts and the geographic range of this agent and contributing to the understanding of pathological and epidemiological aspects of its infection. Further research is needed to fully characterize the strains involved, evaluate their public health relevance and the possible occurrence and impacts in other species of aquatic mammals in Brazil. / Os mamíferos aquáticos são sentinelas de patógenos zoonoticos, os quais podem representar uma ameaça a sua conservação, aos humanos e aos animais domésticos. O género Brucella é responsável pela brucelose, uma das zoonoses mais comuns. Nos mamíferos aquáticos Brucella spp. foi descrita pela primeira vez em 1994 e atualmente duas espécies são reconhecidas nesse grupo: B. ceti e B. pinnipedialis. Nos cetáceos, Brucella spp. tem sido associada a infecção assintomática, doença aguda ou crônica e diversos processos patológicos que podem levar ao encalhe e/ou morte. Nos pinípedes, a patogenicidade de Brucella spp. ainda não é clara. Dados sobre Brucella spp. em mamíferos aquáticos no Oceano Atlântico Sul, particularmente no Brasil, são limitados com uma significativa lacuna de conhecimento mesmo com a rica diversidade. Nesta pesquisa, investigou-se exposição a e/ou infecção por Brucella spp. com métodos sorológicos, moleculares, histopatológicos, imunohistoquimicos e microbiológicos em amostras de mamíferos aquáticos do Brasil armazenadas no banco de tecidos de mamíferos marinhos, Departamento de Patologia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo. Soro de 63 cetáceos [famílias Iniidae (n=37), Delphinidae e Kogiidae (n=26)], 35 pinipedes (Elefante-marinho-do-sul, Mirounga leonina) e 21 peixe-bois marinhos (Trichechus manatus) foi testado pelo Rosa de Bengala, um kit comercial de ensaio imunossorvente ligado a enzima de competição (c-ELISA) e a prova de soroaglutinação lenta em tubo (SAT; c-ELISA positivos selecionados) para detecção de anticorpos anti-Brucella spp. Em adição, DNA de amostras selecionadas de 124 cetáceos, 4 pinípedes e 1 peixe-boi marinho foram analisadas pelo PCR convencional e/ou em tempo real (qPCR) tendo como alvo o gênero Brucella spp. Realizou-se cultivo, histopatologia e imunohistoquimica (IHQ) nas amostras dos indivíduos expostos ou infectados (positivos na sorologia e/ou PCR convencional/qPCR; n=13). Anticorpos anti-Brucella spp. foram detectados em 3/35 (8.6%) dos M. leonina testados enquanto cetáceos das famílias Iniidae e Kogiidae e os peixe-bois foram negativos. DNA de Brucella spp. foi detectado em 4/124 (3.2%) dos cetáceos analisados por PCR convencional/qPCR: um golfinho-climene (Stenella clymene) com brucelose aguda, positivo pela sorologia e IHQ; e três indivíduos adicionais sem soro disponível: uma Franciscana (Pontoporia blainvillei), assintomática, positiva pela qPCR e IHQ; um caso de brucelose crônica em um golfinho-rotador (Stenella longirostris), apresentando osteoartrite fibrinosupurativa atlantoccipital com formação de abcesso, positivo pela qPCR e IHQ; um boto-cinza (Sotalia guianensis), positivo pela PCR convencional/qPCR e IHQ e previamente diagnosticado com morbillivirus dos cetáceos. Apesar da PCR negativa, lesões compatíveis com brucelose foram encontradas em um S. clymene e uma orca-pigmeia (Feresa attenuata), ambos positivos pela sorologia e IHQ. Exposição e/ou infecção por Brucella spp. foi confirmada pela sorologia e/ou IHQ positiva em três baleia-piloto-de-aleta-curta (Globicephala macrorhynchus), dois golfinhos cabeça de melão (Peponocephala electra), um golfinho nariz de garrafa (Tursiops truncatus) e um S. clymene. A maior parte dos cetáceos expostos a/ou infectados por Brucella spp. foram provenientes do estado de Ceará, nordeste do Brasil. A cultura não foi bem-sucedida, prejudicando a classificação das cepas envolvidas. Todos os pinípedes e peixe-bois testados foram negativos na PCR. Triagem oportunistico para avaliar exposição a Leptospira spp. por meio do teste de aglutinação microscópica nos soros testados para Brucella spp. foi negativo. Em conclusão, confirmou-se exposição a Brucella spp., infecção assintomática, brucelose aguda e crônica e coinfecção por Brucella spp. e outros agentes patogênicos. Dentro de nosso conhecimento, esta pesquisa constitui o primeiro trabalho de longo prazo sobre Brucella spp. em mamíferos aquáticos na América do Sul, ampliando a sua faixa de hospedeiros e localização geográfica e contribuindo na compreensão dos aspectos patológicos e epidemiológicos de sua infecção. Pesquisas adicionais são necessárias para caracterizar as cepas envolvidas, avaliar a sua relevância na saúde publica, bem como sua possível ocorrência e impactos em outras espécies de mamíferos aquáticos no Brasil.