Common Bottlenose Dolphins Tursiops Truncatus Research Articles

Whales and dolphins of the Adriatic Sea

The Adriatic Sea is one of the Mediterranean areas most exposed to cumulative human stressors. This semienclosed and largely shallow basin has been subjected to intensive exploitation and destructive fishing practices for decades, resulting in biodiversity decline and poor ecosystem health. Diversity of cetaceans is lower than in other parts of the Mediterranean, and the extant dolphins and whales have been facing threats that include the combined effects of habitat loss and degradation, prey depletion, incidental mortality and injury caused by fisheries, anthropogenic noise, chemical contamination and climate change. Here, we report information for the nine cetacean species known to occur in the basin (classified as either regular, visitor or vagrant), plus three species characterized by a single record. For these species, we review evidence from field research and other studies – with a bias towards the common bottlenose dolphin Tursiops truncatus (by far the most intensively-studied cetacean in this area). We also describe and characterize the main threats to cetaceans in the Adriatic, relying on recent literature as well as historical information that helps frame the present status of cetaceans in the context of past human impacts (particularly the extensive killing campaigns conducted until the 1960s). Finally, we provide management recommendations to inform and guide the action that must be taken in compliance with extant legislation, marine conservation directives and international commitments to protect marine biodiversity.

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.

Bottlenose dolphin distribution in a Mediterranean area exposed to intensive trawling

The Adriatic Sea is one of the areas most exposed to trawling, worldwide. We used four years (2018–2021) and 19,887 km of survey data to investigate factors influencing daylight dolphin distribution in its north-western sector, where common bottlenose dolphins Tursiops truncatus routinely follow fishing trawlers. We validated Automatic Identification System information on the position, type and activity of three types of trawlers based on observations from boats, and incorporated this information in a GAM-GEE modelling framework, together with physiographic, biological and anthropogenic variables. Along with bottom depth, trawlers (particularly otter and midwater trawlers) appeared to be important drivers of dolphin distribution, with dolphins foraging and scavenging behind trawlers during 39.3% of total observation time in trawling days. The spatial dimension of dolphin adaptations to intensive trawling, including distribution shifts between days with and without trawling, sheds light on the magnitude of ecological change driven by the trawl fishery.

Public knowledge and awareness of the conservation of the common bottlenose dolphin (Tursiops truncatus) along the central coast of Peru

Abstract Although the coastal common bottlenose dolphin Tursiops truncatus is under legal protection, this species is threatened by bycatch and direct hunting along the Peruvian coast. Species conservation can be better achieved if communities are empowered with knowledge and actions to mitigate negative impacts on vulnerable species. Thus, it is important to understand people's degree of knowledge about a species and its conservation issues. This study evaluated the knowledge and perception of aspects of the biology, ecology and conservation status of the common bottlenose dolphin in coastal communities along the central coast of Peru. Structured questionnaires were completed by 197 people, and seven people participated in open‐ended interviews in January 2022. Most respondents were knowledgeable of the distribution and ecology of common bottlenose dolphins. Seventy per cent of those surveyed were aware of some threats to this species. Some respondents were eager to take part in actions that would aid in the conservation of the species. However, 69.5% (n = 137) were unfamiliar with the word ‘bycatch’. Charismatic species can engage the public in conservation actions. This research shows that common bottlenose dolphin can be used as a flagship species for marine conservation. It is important to actively involve all stakeholders, particularly fishers, in conservation efforts and the measures that need to be taken to improve common bottlenose dolphin conservation.

Tension pneumothorax in small odontocetes.

Pneumothorax, the accumulation of air in the pleural cavity, occurs when air enters the pleural space by the pleuro-cutaneous, pleuro-pulmonary, or pleuro-oesophageal-mediastinal route. Tension pneumothorax is an infrequent and severe form of pneumothorax where a positive pressure in the pleural space is built up during at least part of the respiratory cycle, with compression of both lungs and mediastinal vessels, and, if unilateral, with midline deviation towards the unaffected hemithorax. We describe 9 cases of tension pneumothorax in 3 species of small cetaceans (striped dolphin Stenella coeruleoalba, common dolphin Delphinus delphis, and common bottlenose dolphin Tursiops truncatus) from the western Mediterranean coast of Spain, and one case from a dolphinarium. Computed tomography (CT) imaging performed in 2 carcasses before necropsy showed lung compression, midline deviation, and pressure on the diaphragm, which was caudally displaced. Tension pneumothorax was recognized at necropsy by the presence of pressurized air in one of the hemithoraces. Seven of the pneumothorax cases were spontaneous (2 primary and 5 secondary to previous lung pathology). In the other 2 dolphins, the pneumothorax was traumatic, due to oesophageal-pleural perforation or rib fractures. We hypothesize that pneumothorax in dolphins is predominantly tensional because of their specific anatomical and physiological adaptations to marine life and the obligate exposure to extreme pressure changes as diving mammals.

Determinants of variability in signature whistles of the Mediterranean common bottlenose dolphin

One of the most studied aspects of animal communication is the acoustic repertoire difference between populations of the same species. While numerous studies have investigated the variability of bottlenose dolphin whistles between populations, very few studies have focused on the signature whistles alone and the factors underlying differentiation of signature whistles are still poorly understood. Here we describe the signature whistles produced by six distinct geographical units of the common bottlenose dolphin (Tursiops truncatus) in the Mediterranean Sea and identify the main determinants of their variability. Particularly, the influence of the region (proxy of genetic distance), the geographic site, and the environmental (sea bottom-related) and demographical (population-related) conditions on the acoustic structure of signature whistles was evaluated. The study provides the first evidence that the genetic structure, which distinguishes the eastern and western Mediterranean bottlenose dolphin populations has no strong influence on the acoustic structure of their signature whistles, and that the geographical isolation between populations only partially affected whistle variability. The environmental conditions of the areas where the whistles developed and the demographic characteristics of the belonging populations strongly influenced signature whistles, in accordance with the “acoustic adaptation hypothesis” and the theory of signature whistle determination mediated by learning.

Interannual shifts in sea surface temperature and chlorophyl drive the relative abundance and group size of common bottlenose dolphins Tursiops truncatus on the Southeast Gulf of California

Despite being one of the most common odontocetes off Sinaloa (Mexican Pacific coast), basic studies on the ecology of common bottlenose dolphins (Tursiops truncatus) are scarce in the region. This study aimed to describe changes in the relative abundance, group size, and behavior of this species during 2007 – 2012. We used boat-based surveys and satellite images of sea surface temperature (SST) and chlorophyll-a (Chl-a) to model changes in dolphin relative abundance (RA) over time, using correlations in time series analyses. Overall, mean RA was 3.6 dolphins h-1 (SD = 8.0), and significantly higher RA (6.4 –16.7 dolphins h-1) occurred in 2008, 2011, 2012, which was concurrent with hydrographic effects of La Niña oceanographic conditions, as well as during the upwelling season (February – April) (SST: 17.3 – 25.0 °C; Chl-a: 3.7 – 21.4 mg m-3). Conversely, significantly lower RA values (0.5 – 3.8 dolphins h-1) occurred in 2007 and 2010 that were likely associated with El Niño effects on the biological productivity of the area (Chl-a: 0.3 – 7.6 mg m-3). We found significant correlations between monthly Chl-a and SST average values with mean bottlenose dolphins RA, and lags (22 – 29 days) in the trophic response to variations of the hydrographic parameters. Significantly larger dolphin groups were recorded during La Niña years possibly because of the higher availability of their prey. This hypothesis is supported by higher feeding frequencies (35 – 73%) observed during the upwelling seasons, especially during La Niña conditions, whereas the most frequent behavior throughout all other years was traveling (28 – 69%). Our results show that RA and group size of bottlenose dolphins inhabiting the waters off Sinaloa, Mexico, are likely influenced by the changes in hydrographic parameters, especially during extreme climatic events.

Parameterizing animal sounds and motion with animal-attached tags to study acoustic communication

Stemming from the traditional use of field observers to score states and events, the study of animal behaviour often relies on analyses of discrete behavioural categories. Many studies of acoustic communication record sequences of animal sounds, classify vocalizations, and then examine how call categories are used relative to behavioural states and events. However, acoustic parameters can also convey information independent of call type, offering complementary study approaches to call classifications. Animal-attached tags can continuously sample high-resolution behavioural data on sounds and movements, which enables testing how acoustic parameters of signals relate to parameters of animal motion. Here, we present this approach through case studies on wild common bottlenose dolphins (Tursiops truncatus). Using data from sound-and-movement recording tags deployed in Sarasota (FL), we parameterized dolphin vocalizations and motion to investigate how senders and receivers modified movement parameters (including vectorial dynamic body acceleration, “VeDBA”, a proxy for activity intensity) as a function of signal parameters. We show that (1) VeDBA of one female during consortships had a negative relationship with centroid frequency of male calls, matching predictions about agonistic interactions based on motivation-structural rules; (2) VeDBA of four males had a positive relationship with modulation rate of their pulsed vocalizations, confirming predictions that click-repetition rate of these calls increases with agonism intensity. Tags offer opportunities to study animal behaviour through analyses of continuously sampled quantitative parameters, which can complement traditional methods and facilitate research replication. Our case studies illustrate the value of this approach to investigate communicative roles of acoustic parameter changes.Significance statementStudies of animal behaviour have traditionally relied on classification of behavioural patterns and analyses of discrete behavioural categories. Today, technologies such as animal-attached tags enable novel approaches, facilitating the use of quantitative metrics to characterize behaviour. In the field of acoustic communication, researchers typically classify vocalizations and examine usage of call categories. Through case studies of bottlenose dolphin social interactions, we present here a novel tag-based complementary approach. We used high-resolution tag data to parameterize dolphin sounds and motion, and we applied continuously sampled parameters to examine how individual dolphins responded to conspecifics’ signals and moved while producing sounds. Activity intensity of senders and receivers changed with specific call parameters, matching our predictions and illustrating the value of our approach to test communicative roles of acoustic parameter changes. Parametric approaches can complement traditional methods for animal behaviour and facilitate research replication.

Mapping the Exposure of Pantropical Spotted Dolphins and Common Bottlenose Dolphins to Different Categories of Vessel Traffic in Maui Nui, Hawai‘i

The increase and diversification of vessel traffic worldwide has resulted in a variety of known disturbances to dolphins. As a remote island chain, the Hawaiian Islands rely heavily on the marine environment for transportation, recreation, and fishing that aggregates into significant levels of vessel traffic. Given the known presence of dolphins in this region, there is a gap in knowledge regarding the relative exposure risk that vessel traffic poses to island-associated dolphin populations in Hawai‘i. This research identified the spatial distribution of pantropical spotted dolphins (Stenella attenuata) and common bottlenose dolphins (Tursiops truncatus) and determined the extent of their overlap with various categories of vessel traffic in Maui Nui, Hawai‘i. Species distribution was determined using kernel density estimates based on sighting data from 50 spotted dolphin sightings and 75 bottlenose dolphin sightings collected from 2013 to 2018. A combination of vessel GPS and Automatic Identification Systems (AIS) vessel tracks were used to quantify vessel traffic within the study area, resulting in 22,464 vessel tracks that were subsequently compiled into categories for analysis from 2014 to 2017. Risk of vessel exposure between vessels and dolphins, or co-occurrence, was determined by calculating the product of predicted dolphin density and predicted vessel density. Both species were exposed to vessel traffic risk over 100% of their distribution, but their highest exposure risk varied spatially, with high risk defined as > 0.25 on a normalized scale of low (0) to high (1) risk. The highest vessel exposure risk for spotted dolphins occurred in deeper, offshore waters, while the highest risk for bottlenose dolphins was in shallow, coastal waters. The vessel categories with the largest area of high risk to spotted dolphins were tour vessel and commercial fishing vessel traffic, while commercial transportation traffic had the highest exposure risk for bottlenose dolphins. This article provides baseline information for understanding the vulnerability of two island-associated dolphin populations to the threat of vessel traffic and highlights the differences in relative exposure risk based on species and vessel categories.

Endogenous Ouabain in Human and Animal Models of Hypoxia

Endogenous ouabain (EO) is a steroid hormone secreted by the adrenal glands, usually associated with adverse cardiovascular effects. However, recent studies have highlighted its possible role in blood pressure control and in cardio-renal damage, and it seems to be involved in the adaptive response to hypoxia. The aim of this study is to detect the EO in human and animal models of hypoxia. We collected blood samples from seven competitive elite apnea divers, 11 noncompetitive elite apnea divers, and 26 healthy control subjects. Animal blood samples were collected from 16 common bottlenose dolphins (Tursiops truncatus), two phocids and two otariids kept under human care, and 11 wild loggerhead sea turtles (Caretta caretta) hosted in two rescue centers. We measured EO plasma concentrations with a Scintillation Proximity Assay. In elite apnea divers and healthy control subjects, EO plasma concentrations were positively correlated to weight (p < 0.05). Elite apnea divers showed statistically significant (p < 10-6) higher EO plasma concentrations compared to healthy subjects without any diving experience or experience in other sports activities involving breath-holding. In dolphins, EO plasma concentrations were positively correlated to age, total length, and weight (p < 0.05). In loggerhead sea turtles, EO plasma concentrations were negatively correlated to total length and weight (p < 0.05). In pinnipeds, correlation analysis was not performed due to the small number of animals. Herein, we demonstrate, for the first time, that different taxa, phylogenetically distant from each other and which perform apneas without reporting neurological damages, express EO. Our findings, although preliminary, are in line with the recently emerging hypothesis on a possible role of EO in the adaptive response to hypoxia and represent a helpful hint for future investigations aimed to identify novel molecules useful to treat very disabling pathological conditions such as idiopathic pulmonary arterial hypertension or obstructive sleep apnea.

Potential Infanticide Attempt of Common Bottlenose Dolphins (Tursiops truncatus) on a Young Calf in a Tropical Caribbean Atoll

Potential Infanticide Attempt of Common Bottlenose Dolphins (Tursiops truncatus) on a Young Calf in a Tropical Caribbean Atoll

Utility of Red Tide (Karenia brevis) Monitoring Data as a Predictive Tool to Estimate Brevetoxin Accumulation in Live, Free-Ranging Marine Mammals

Exposure of common bottlenose dolphins (Tursiops truncatus) to brevetoxins (PbTx) produced by blooms of the toxic phytoplanktonKarenia brevisfrequently results in severe health impacts, including illness and large-scale mortality events. Although PbTx accumulation in dead-stranded dolphins is well documented, there are limited data for corresponding brevetoxin exposure in live dolphins. In addition, the severity of impacts on living survivors of such toxic blooms is difficult to assess due to a lack of data on the relationship betweenK. brevisbloom severity and corresponding PbTx concentrations in exposed animals. Here we present results of PbTx analysis of urine, serum, milk, gastric fluid, and feces samples collected from live, free-ranging dolphins (n= 253) from Sarasota Bay, Florida during 2000–2018, and investigate the relationship between PbTx concentrations detected and correspondingK. breviscell abundances that are temporally (within 30 days) and spatially (within 16 km) associated with each individual. We found that 28% of dolphins were associated with elevatedK. brevisabundances (10,000–60,000,000 cells/L), with 41% (n= 104) of dolphins testing positive for PbTx in at least one sample type. The proportion of PbTx-positive animals was significantly greater in animals exposed to elevated cell abundances vs. those exposed to background cell abundances (<10,000 cells/L), with 60 and 34% testing positive, respectively (p< 0.001). PbTx was detected most frequently in feces (57%,n= 38), followed by gastric (35%,n= 37), urine (32%,n= 55), and blood (7%,n= 17). PbTx concentrations by sample type were highest in feces (2–231 ng/g; mean 46), followed by urine (0.8–90 ng/g; mean 7.2), gastric (0.8–61 ng/g; mean 12), and blood (0.3–5 ng/g; mean 1.3). Regression analyses ofK. breviscell abundance as an index of exposure vs. corresponding PbTx concentration found no statistically significant relationship for feces (p= 0.120), gastric (p= 0.349), urine (p= 0.053), or blood (p= 0.729) samples. PbTx concentrations typically ranged over two orders of magnitude between minimum and maximum values and did not scale with corresponding indices of exposure, which ranged over three orders of magnitude or more. Our results indicate thatK. breviscell abundance alone is a poor predictor of brevetoxin accumulation in bottlenose dolphins, and suggest that alternative methods (e.g., endocrine or immunological biomarkers) should be investigated as more appropriate methods for determining the severity of health impacts due to red tides.

How to Work on a Non-endangered Species and Contribute to Cetacean Conservation: An Example by the Sarasota Dolphin Research Program

The world’s most endangered small cetaceans are found in countries many miles from Sarasota Bay and its common bottlenose dolphins (Tursiops truncatus). Information on the ecology and threats to many of these endangered cetaceans is often far more limited than that on bottlenose dolphins, with the IUCN Red Data List describing many species as “data deficient.” In many developing nations where these rare species occur, resources for research and monitoring are scant, and logistical challenges further limit research into marine mammal health and population status and their threats. The Sarasota Dolphin Research Program (SDRP) has tackled this problem by using the bottlenose dolphin as a model for cetacean species in other parts of the world and using its resources to assist scientists working with more endangered species of cetacean. The celebration of 50 years of study by the SDRP exemplifies how using long-term data on known individuals can advance the fields of cetacean behavior, ecology, life history, physiology, toxicology, and medicine, all providing information for informing certain conservation actions. The Sarasota team has used their work to inform conservation policy both home and abroad.

Beyond genetic differences: epigenetic variation in common bottlenose dolphins Tursiops truncatus from contrasting marine ecosystems

Recent genetic and morphological studies have indicated an incipient ecological divergence between 2 ecotypes of common bottlenose dolphinTursiops truncatusin the Southwestern Atlantic. However, genetic variation is not the only molecular mechanism that alters the phenotype of these animals: epigenetics can also influence phenotypic plasticity, as well as the ecological adaptation and divergence of natural populations. Nevertheless, very little is known about the role that epigenetics plays in the population ecology of marine mammals. In this work, we tested whether there are differences in DNA methylation patterns between a coastal and an offshore ecotype of common bottlenose dolphin. Methylation patterns were analyzed using the methylation-sensitive amplified polymorphism technique on biopsy samples collected from animals of both ecotypes. We found consistent differences in DNA methylation patterns between coastal and offshore individuals. We also confirmed the genetic differences described in previous studies, indicating that the divergence between ecotypes has both genetic and epigenetic components. Our data show that it is possible to differentiate animals from the coastal and offshore ecotypes using DNA methylation markers, supporting the hypothesis that contrasting environments—which are decisive for the ecological divergence of these populations—lead to epigenetic modifications in common bottlenose dolphins.

Brucella ceti sequence type 23, 26, and 27 infections in North American cetaceans.

Brucella ceti infection is associated with a variety of disease outcomes in cetaceans globally. Multiple genotypes of B. ceti have been identified. This retrospective aimed to determine if specific lesions were associated with different B. ceti DNA sequence types (STs). Characterization of ST was performed on 163 samples from 88 free-ranging cetaceans, including common bottlenose dolphin Tursiops truncatus (T.t.; n = 73), common short-beaked dolphin Delphinus delphis (D.d.; n = 7), striped dolphin Stenella coeruleoalba (n = 3), Pacific white-sided dolphin Lagenorhynchus obliquidens (n = 2), sperm whale Physeter macrocephalus (n = 2), and harbour porpoise Phocoena phocoena (n = 1), that stranded along the coast of the US mainland and Hawaii. ST was determined using a previously described insertion sequence 711 quantitative PCR. Concordance with 9-locus multi-locus sequence typing was assessed in a subset of samples (n = 18). ST 26 was most commonly identified in adult dolphins along the US east coast with non-suppurative meningoencephalitis (p = 0.009). Animals infected with ST 27 were predominately perinates that were aborted or died shortly after birth with evidence of in utero pneumonia (p = 0.035). Reproductive tract inflammation and meningoencephalitis were also observed in adult T.t. and D.d. with ST 27, though low sample size limited interpretation. ST 23 infections can cause disease in cetacean families other than porpoises (Phocoenidae), including neurobrucellosis in D.d. In total, 11 animals were potentially infected with multiple STs. These data indicate differences in pathogenesis among B. ceti STs in free-ranging cetaceans, and infection with multiple STs is possible.

Using the otolith sulcus to aid in prey identification and improve estimates of prey size in diet studies of a piscivorous predator.

Diet studies are fundamental for understanding trophic connections in marine ecosystems. In the southeastern US, the common bottlenose dolphin Tursiops truncatus is the predominant marine mammal in coastal waters, but its role as a top predator has received little attention. Diet studies of piscivorous predators, like bottlenose dolphins, start with assessing prey otoliths recovered from stomachs or feces, but digestive erosion hampers species identification and underestimates fish weight (FW). To compensate, FW is often estimated from the least affected otoliths and scaled to other otoliths, which also introduces bias. The sulcus, an otolith surface feature, has a species‐specific shape of its ostium and caudal extents, which is within the otolith edge for some species. We explored whether the sulcus could improve species identification and estimation of prey size using a case study of four sciaenid species targeted by fisheries and bottlenose dolphins in North Carolina. Methods were assessed first on otoliths from a reference collection (n = 421) and applied to prey otoliths (n = 5,308) recovered from 120 stomachs of dead stranded dolphins. We demonstrated in reference‐collection otoliths that cauda to sulcus length (CL:SL) could discriminate between spotted seatrout (Cynoscion nebulosus) and weakfish (Cynoscion regalis) (classification accuracy = 0.98). This method confirmed for the first time predation of spotted seatrout by bottlenose dolphins in North Carolina. Using predictive models developed from reference‐collection otoliths, we provided evidence that digestion affects otolith length more than sulcus or cauda length, making the latter better predictors. Lastly, we explored scenarios of calculating total consumed biomass across degrees of digestion. A suggested approach was for the least digested otoliths to be scaled to other otoliths iteratively from within the same stomach, month, or season as samples allow. Using the otolith sulcus helped overcome challenges of species identification and fish size estimation, indicating their potential use in other diet studies.

Cranial Morphometrics of a Stranded Common Bottlenose Dolphin Tursiops truncatus (Montagu, 1821) in Mersin Bay (Northeastern Mediterranean, Turkey)

On 10 November 2017, a young male common bottlenose dolphin Tursiops truncatus (Montagu, 1821), 185 cm in total length (TL), was found dead on the Mersin Marina (36°46'065"N, 34°34'212"E) in Northeastern Mediterranean coast of Turkey. Measurements of the sample performed and documented. The specimen buried to obtain the skeleton of the individual. At the end of this process, the sample was deposited in the Museum of the Systematic, Faculty of Fisheries, Mersin University, (Catalogue no: MEUMC-17- 11-001). The morphometric measurements can contribute to ongoing fisheries biology and taxonomic studies of T. truncatus from Mediterranean Sea waters. During routine fishing activities, common bottlenose dolphins can be caught in fishing nets and drowned. This issue leads to an extra population loss in addition to environmental factors that cause dolphin deaths. At the national level, measures should be implemented to protect dolphins and other marine species caught off -target.

Habitat use models of spatially auto-correlated data: a case study of the common bottlenose dolphin, Tursiops truncatus truncatus, in southeastern Brazil

ABSTRACTA common approach to studying habitat use in cetaceans is to conduct line-transect surveys, to investigate their distribution. In developing countries, there are limited resources for data collection. One solution is to employ field surveys to collect a wide range of ecological and behavioural data, for which a haphazard sampling schedule is adopted, to optimize the cost–benefit ratio. As with line-transect surveys, the haphazard sampling may lead to spatial autocorrelation (SAC), an overlooked problem in ecology. Here, we investigated common bottlenose dolphins (Tursiops truncatus truncatus) habitat use on an upwelling area and tested an approach that can improve model-based inference on auto-correlated data. We collected data in Cabo Frio, Rio de Janeiro, photo-identified 429 individuals and compared the predictions and model coefficients of standard generalized linear model (GLM) without correcting for spatial autocorrelation with a spatial eigenvector generalized linear model (SEV-GLM) which compensates for SAC. Our best SEV-GLM predicted dolphins are more likely to occur on cold waters with increased chlorophyll concentration, indicating dolphins are influenced by the upwelling. Moreover, by correcting for SAC, our models had a better fit to data, magnified the relevance of significant variables and showed smaller and less clumped residuals than when not correcting.

Toxoplasma gondii in cetaceans of Brazil: a histopathological and immunohistochemical survey.

Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. In cetaceans, T. gondii infection is a significant cause of morbidity and mortality. Despite the worldwide range and broad cetacean host record of T. gondii infection, there is limited information on toxoplasmosis in cetaceans from the Southern hemisphere. We investigated the occurrence of T. gondii by histopathology and immunohistochemistry in tissue samples of 185 animals comprising 20 different cetacean species from Brazil. Three out of 185 (1.6%) animals presented T. gondii-associated lesions: a captive killer whale Orcinus orca, a free-ranging common bottlenose dolphin Tursiops truncatus and a free-ranging Guiana dolphin Sotalia guianensis. The main lesions observed in these animals were necrotizing hepatitis, adrenalitis and lymphadenitis associated with protozoal cysts or extracellular tachyzoites presenting immunolabeling with anti-T. gondii antibodies. This study widens the spectrum of species and the geographic range of this agent in Brazil, and provides the first reports of T. gondii infection in a captive killer whale and in a free-ranging common bottlenose dolphin in South America.

GIS Investigation of the relationship of sex and season on the population distribution of common bottlenose dolphins (Tursiops truncatus) in Charleston, South Carolina

ABSTRACT The Charleston Estuarine System Stock (CESS) of common bottlenose dolphins (Tursiops truncatus) has been the focus of population monitoring for the past 20 years. Photo-id studies have determined abundance and survival estimates for this population, which exhibits high site fidelity in this area. However, fine-scale distribution, utilization patterns, and the driving forces behind these patterns are lacking. Using historical photo-id data and a novel application of geographic information system (GIS) analysis, the present study identified core use areas within Charleston Harbor, as well as patterns specific to sexes and seasons. Photo-id data of 319 dolphins sighted 11 times or more during 2004–2009 were analyzed. Heat maps were developed to examine spatial distributions using kernel density estimates (KDE) and were compared between sexes and seasons. Multiple high-density core use areas were identified for this population, with the most noteworthy near the mouth of the harbor toward the Atlantic Ocean. Fine-scale distribution varied across sexes, as well as seasons. Some areas were identified as more specifically inhabited by one sex, while other areas overlapped between sexes. Females were more tightly concentrated within their distribution while males were more dispersed. Although population distribution varied across seasons, sex distributions remained.