Le concept d'Umwelt de Jakob von Uexküll considère les animaux comme des sujets qui habitent leur propre univers subjectif qui est déterminé par la perception sensorielle de l'animal et ses capacités cognitives. Le dauphin apparait être une espèce intéressante pour étudier l'Umwelt, car les cétacés ont subi un changement radical de mode de vie au cours de l'évolution. Ces mammifères sont passés d'une vie terrestre à une vie aquatique. Bien que les grands dauphins soient intensivement étudiés, des recherches sur leur perception sensorielle sont encore nécessaires. Ici, nous avons étudié certains aspects de l'Umwelt des dauphins en nous interrogeant sur: (1) l'organisation de leur Umwelt acoustique nocturne ; (2) ce que la production de copies vocales par les dauphins peut nous dire sur leur perception de leur environnement ; (3) s'ils sont capables de percevoir des goûts (4) ou des odeurs ; (5) s'ils sont sensibles aux stimuli magnétiques. Nous avons constaté que l'Umwelt nocturne des dauphins a été caractérisé par une activité vocale avec des patterns temporels qui comprenaient également des copies vocales des sons que les dauphins avaient entendus au cours de la journée. Il s'agit d'une nette séparation entre la formation de la mémoire auditive et la production de copies vocales. Les copies pourraient être des répétitions nocturnes vocalement exprimées des événements de la journée. Ainsi, les vocalisations peuvent servir d'indicateurs d'événements ou d'objets qui ont un sens pour les dauphins. En ce qui concerne les capacités perceptives des dauphins, nous avons constaté qu'ils étaient sensibles aux stimuli liés à l'alimentation à la fois sur les plans gustatif et olfactif. Ils peuvent utiliser cette capacité pour localiser et / ou évaluer la nature de leur proie. En outre, les dauphins ont répondu à un stimulus magnétique, ce qui suggère qu'ils sont magnétosensibles, cela pourrait être utile pour la navigation. Jusqu'à présent, la chimio- et la magnétoréception n'ont pas été considérées sérieusement comme potentiellement fonctionnelles chez les dauphins. Les résultats obtenus au cours de cette thèse ont permis de combler certaines des lacunes qui subsistaient dans la connaissance de l'Umwelt du dauphin et contribuent ainsi à une meilleure compréhension de cette espèce. En outre, ils montrent que des aspects importants de la biologie d'espèces pourtant intensivement étudiées peuvent être encore méconnus. Cela nous rappelle l'importance de garder une grande ouverture d'esprit lorsque l'on étudie un sujet. / The Umwelt concept of Jakob von Uexküll considers animals as subjects that inhabit their own subjective universe which is determined by the animal’s sensory perception and cognitive abilities. Dolphins present an interesting species to investigate its Umwelt because cetaceans underwent a drastic change in lifestyle in the course of evolution because these mammals returned from a terrestrial life back into the water. Although bottlenose dolphins are intensively studied there are still many knowledge gaps. Here we studied some aspects of the dolphins’ Umwelt by asking: (1) how their nocturnal acoustic Umwelt is arranged; (2) what the production of vocal copies can tell us about the dolphins’ perception of their environment; (3) whether they are able to perceive tastes (4) or odours; (5) whether they are sensitive to magnetic stimuli. We found that the dolphins’ nocturnal Umwelt was characterized by a temporally patterned vocal activity that also included vocal copies of sounds that the dolphins had heard during the day. This is a striking separation between auditory memory formation and vocal copy production and the copies might be a vocally expressed nocturnal rehearsal of day events. Thus, vocalizations can serve as possible indicators of events or objects that are meaningful to the dolphins. Regarding dolphins’ perceptive abilities, we found that they were sensitive to both gustatory and olfactory food-related stimuli. They might use this ability to locate and/or evaluate prey. Further, dolphins responded to a magnetic stimulus, suggesting that they are magnetosensitive, what could be useful for navigation. So far, chemo- and magnetoreception have not been considered seriously as potentially functional in dolphins. The results obtained during this thesis fill some of the gaps that still exist in the knowledge of the dolphin’s Umwelt and therefore contribute to a better understanding of this species. Moreover, they illustrate that even already intensively studied species may still hold important facets of their biology to reveal and that research should broaden the view and remain unbiased when studying a topic.

The heterogeneous landscape of Florida Bay provides habitats for a variety of predators and prey. This dissertation examined the bottom-up transfer of affects from environmental variability through prey composition up to competition and predation affects on top predator distribution and foraging ecology in Florida Bay. Line transect surveys for bottlenose dolphins and seabirds were conducted in Florida Bay during the summer months of 2002 - 2005. Photo-identification techniques were implemented to identify individual dolphins. Synoptic with this survey effort, habitat characteristics (temperature, salinity, dissolved oxygen, turbidity, chlorophyll a, depth and bottom type) and prey composition (bottom trawl or gillnet) were sampled. Comparison of envelope maps from generalized additive models determined that predictive capacity of dolphin habitat did not improve by incorporating fish distribution data. However, models of dolphin distribution based solely on environmental proxies of fish distribution resulted in high predictive capacity. During the 2005 summer, shark distribution was sampled using a longline. The abundance of sharks was only correlated to fish catch from trawls on a regional scale. Larger sharks, of species that may threaten dolphins, were only caught in the Gulf zone of the Bay. Analysis of dolphin distribution revealed high individual site and foraging tactic fidelity. Dolphins were spatially coincident with habitat characteristics that encouraged the use of each individual's preferred foraging tactic. Depth was identified as the primary variable determining dolphin foraging tactic choice. Depth plays a significant role in the benthic composition of Florida Bay, which subsequently impacts prey communities and affects dolphin distribution, foraging and social ecology. Ordinations determined that fish distribution was also principally affected by depth and bottom type. Shallow environments frequently corresponded with mudbank habitat (depth < 1m) where the sighting rates of seabirds (cormorants, osprey, pelicans, terns) and foraging dolphins peaked. In conclusion, subtle relief in South Florida's bedrock topography dramatically affect benthic composition within Florida Bay, providing patchy habitats for prey and predators. The Florida Bay ecosystem will change with expected sea level rise, including spatial shifts of mudbank habitats. Top predator populations in Florida Bay will be forced to modify their distribution and foraging ecology accordingly. / Dissertation

In recent years there has been an increased interest in measuring animal personality. It is argued that personality in animals is expressed through the behaviours they display. In this study personality has been investigated in a group of eight captive bottlenose dolphins (Tursiops truncatus). Data from focal samplings were analysed by using behavioural codings and the Five-factor model consisting of Openness to experience, Conscientiousness, Extraversion, Agreeableness and Neuroticism. The results revealed that the dolphins display both distinct personality differences as well as similarities in these factors. By calculating coefficients of association it was found that the dolphins also prefer the company of certain individuals over others. Knowledge of individual personality differences and its implications can be helpful in aspects such as management and reintroduction programs, evolution and genetics and in providing a complementary perspective to explain other behavioural and cognitive studies.

The objective of this thesis was to determine if there were any correlations in the distribution of cetaceans, especially sperm whales (Physeter macrocephalus), pantropical dolphins (Stenella attenuata), bottlenose dolphins (Tursiops truncatus), and Risso’s dolphins (Grampus griseus) in the northern Gulf of Mexico because of the influence of oil and gas production and exploration. This research is important because of the lack of knowledge about the impact of anthropogenic sounds from oil and gas exploration and production (E&P) on cetacean distribution in the Gulf of Mexico. I analyzed cetacean visual line-transect survey results from the Gulf of Mexico for period of 1992 – 2001. I divided this time span into an early period (1992 – 1997) and a late period (1998 – 2001). I overlayed the locations of cetacean sightings and the locations of oil and gas E&P platforms to demonstrate their close association in space, and tested a hypothesis that distribution would shift south correlated with changes in distribution of E&P. I compared the distributions of cetacean sightings in the entire Gulf of Mexico, and separated the Gulf of Mexico into east and west, between the early period and the late period. The east Gulf of Mexico represents an area without oil and gas E&P platforms and the west Gulf of Mexico is the area where oil and gas E&P platforms are located. The null hypothesis for these tests was that there was no difference in cetacean distribution between the early period and the late period. I also compared the distribution of sperm whales, pantropical dolphins, bottlenose dolphins, and Risso’s dolphins in the entire Gulf of Mexico, both east and west, between the early and late periods. I expect if distribution changes were correlated with changes in E&P distribution, then there will be a shift south in the western Gulf. Changes in distribution in the eastern Gulf would not be correlated with E&P. I found that the sightings per unit effort (SPUE) of all cetacean sightings in the entire Gulf of Mexico shifted to the south in the late period, as compared to the early period .The distribution of all cetacean sightings for the late period (1998-2001) was significantly different compared to the distributions of all cetacean sightings in the early period (1992-1997). The SPUE of sperm whale and bottlenose dolphin distributions were shifted to the north in the late period (1998-2001) compared to the early period (1992-1997). While pantropical dolphin distributions were significantly shifted to the south between the two time periods. I observed that the SPUE of all cetaceans sightings in the east Gulf of Mexico for the early period (1992-1997) were shifted to the south compared to the west, which were not different. The SPUE for sperm whales in the east for the early period were marginally shifted to the north in comparison to the west, which were also shifted further north. The SPUE for Risso’s dolphins in the east were shifted further north while in the west SPUE were shifted to the south. The SPUE for pantropical dolphin sightings were shifted to the north in both the east and west regions. While the SPUE for bottlenose dolphin sightings were shifted to the north in both the east and west Gulf of Mexico. My SPUE results suggest that pantropical dolphins, like the total cetaceans examined here, have shifted their distributions in the entire northern Gulf of Mexico to the south. However, in areas of high oil and gas E&P platforms the distributions of sperm whales and bottlenose dolphins did not shift their distributions from the early period to the late period to the south even though these E&P activities have shifted to the south over the past two decades as they expanded into the deeper waters of the northern Gulf of Mexico. Therefore, there is little evidence that large scale changes in the latitudinal distribution of marine mammals in the Northern Gulf have occurred as a result of greater offshore E&P activity.

Bottlenose dolphins inhabiting coastlines and estuaries in Florida have been impacted in the past decade by development, algal blooms, catastrophic pollution, and fishery interactions (FI). Dolphins react to disturbance and environmental stressors by modifying their movements and habitat use, which may put them in jeopardy of conflict with humans. FI plays an increasing role in contributing to dolphin mortalities. I investigated dolphin movements, habitat use, residency patterns, and frequency of FI with sport fishing. Tagging studies with short-term data tags and bolt on radio-transmitters were done in several locations in Florida and the east coast providing fine-scale measurements of swimming, daily travels, and foraging activity. Transit speeds agreed with the predicted mean cost of transport as dolphins spent much of their day and night travelling and resting while swimming. Increased foraging was detected by stomach temperature changes revealing dolphins fed at night with a peak starting just after sunset. Dolphin abundance, site fidelity, ranging, stranding mortality, and community structure was characterized at Choctawhatchee and Pensacola Bays in the Florida Panhandle via surveying and photo-identification. Results showed they made frequent inshore movements, maintained site fidelity to specific areas, and comprised several distinct communities. FI was assessed at offshore reefs and coastal fishing piers near Destin, FL and Orange Beach, AL, showing that some dolphins demonstrate affinity to this activity. Harmful interactions with dolphins on reefs and at fishing piers negatively affect their resident communities. Mitigation of FI is suggested by use of avoidance strategies, gear modifications, and improved fish release practices.

The St. Johns River (SJR; Jacksonville, FL, USA) is a large, brackish, estuarine system characterized by considerable anthropogenic pollution, recurrent harmful algal blooms (HABs), and diverse toxin-producing cyanobacteria. The most prevalent toxins in SJR water samples are microcystins/nodularins (MCs/NODs). Additionally, the SJR provides critical habitat for a genetically and behaviorally distinct estuarine community of bottlenose dolphins (Tursiops truncatus) that routinely uses and strands in low mesohaline and oligohaline areas of the river. This population has been subject to two unusual mortality events (UME) since 2010 and has since been described as having substantial declines in population health, characterized by widespread dermatitis and emaciation. Additionally, three dolphins have been recovered from low salinity habitats with epidermal algal mats. Because dolphin illness and strandings overlapped temporally and spatially with confirmed cyanobacterial blooms in the SJR, there is concern that estuarine dolphin health may be declining due to exposure to toxic cyanobacteria and HAB events. Specific to this study, the SJR estuarine community was considered a high-risk group for cyanotoxin exposure in relation to coastal animals. This study analyzed all available hepatic tissues for estuarine dolphins, and used samples from coastal individuals that stranded outside of the known cyanotoxin bloom season as controls. Three analytical methods were used to determine MCs/NODs presence in dolphin liver and epidermal algal mat samples. An Adda ELISA and LC-MS/MS were used to determine free MCs/NODs presence while the MMPB technique was used to determine total (bound and free) concentrations and as confirmatory analyses. ELISA analyses produced high values that were not supported by concurrent LC-MS/MS or MMPB analyses, indicative of false positives. MMPB testing resulted in low-level total MCs/NODs detection in some specimens. Results indicate that both estuarine and coastal dolphins are exposed to MCs/NODs, with potential toxic and immune health impacts.

Bottlenose dolphins (Tursiops truncatus) and other odontocete cetaceans rely on sound for communication, navigation, and foraging. Therefore, hearing is one of their primary sensory modalities. Both natural and anthropogenic noise in the marine environment could mask the ability of free-ranging dolphins to detect sounds, and chronic noise exposure could cause permanent hearing losses. In addition, several mass strandings of odontocete cetaceans, especially beaked whales, have been correlated with military exercises involving mid-frequency sonar, highlighting unknowns regarding hearing sensitivity in these animals.Auditory evoked potential (AEP) methods are attractive over traditional behavioral methods for measuring the hearing of marine mammals because they allow rapid assessments of hearing sensitivity and can be used on untrained animals. The goals of this study were to 1.) investigate the differences among underwater AEP, in-air AEP, and underwater behavioral heari ng measurements using two captive bottlenose dolphins, 2.) investigate the hearing abilities of a population of free-ranging bottlenose dolphins in Sarasota Bay, Florida, using AEP techniques, and 3.) report the hearing abilities of a stranded juvenile beaked whale (Mesoplodon europaeus) measured using AEP techniques.For the two captive dolphins, there was generally good agreement among the hearing thresholds determined by the three test methods at frequencies above 20 kHz. At 10 and 20 kHz, in-air AEP audiograms were substantially higher (about 15 dB) than underwater behavioral and underwater AEP audiograms.For the free-ranging dolphins of Sarasota Bay, Florida, there was considerable individual variation, up to 80 dB between individuals, in hearing abilities. There was no relationship between age, gender, or PCB load and hearing sensitivities. Hearing measured in a 52-year-old captive-born bottlenose dolphin showed similar hearing thresholds to the Sarasota dolphins up to 80 kHz, but exhibited a 50 dB drop in sensitivity at 120 kHz.Finally, the beaked whale was most sensitive to high frequency signals between 40 and 80 kHz, but produced smaller evoked potentials to 5 kHz, the lowest frequency tested. The beaked whale hearing range and sensitivity were similar to other odontocetes that have been measured.

Human interaction greatly influences the behavior and distribution of bottlenose dolphins (Tursiops truncatus). This project focuses on the distribution and behavior of bottlenose dolphins in the Drowned Cayes, Belize. Prior to the 2000s, the area was relatively undeveloped and undisturbed and had minimal human activity. Since the turn of the millennium, development and ecotourism activity has flourished in the area, increasing by more than 800,000 visitors from 1998-2006. Boat-based surveys were conducted in 2015 and were combined with previous survey data collected from 2005-2012 and compared to behavioral survey results from 1999-2000. Total dolphin observation time as a percent of total survey time and average number of dolphins per sighting were 17.2% and 2.7 in 1999-2000 and 10.8% and 1.6 for 2005-2015. The low number of dolphins and the low observation times suggest that the dolphin population in the Drowned Cayes have decreased since the 1990s. Eighty-nine percent of the total observation time for 2015 occurred on days in which there were zero cruise ships in the area suggesting that this decline may be in relation to increased human activity. Furthermore, foraging was the main behavior observed for both 1999-2000 and 2005-2015 data sets, suggesting that the Drowned Cayes area is used as a foraging ground. However, in 1999-2000 the foraging percentage was significantly higher than the 2005-2015 data set, dropping 28.9% and there was a 23.6% increase in traveling behavior between the two data sets. This could be a result of increased human activity. Additionally, survey photographs and results were used in the creation of the first dolphin photo identification database for the country. The guidelines used for photo analysis for photo quality and fin distinctiveness were tested to determine if they are easy to use and give consistent and reliable results regardless of judge. An intraclass correlation model calculated substantial agreement (ICC = 0.7) between judges’ scores, demonstrating consistent results, regardless of experience level. Therefore, the guideline can be used as a standard among multiple researchers.

Dolphins use stereotyped, individually distinctive, frequency modulated whistles, referred to as signature whistles, in order to broadcast their identity. In this study, we trained six dolphins at Kolmården Zoo, Sweden, to be called over, either upon hearing their own signature whistle (SW) or upon hearing a biologically irrelevant ”trivial” sound (TS), with the aim to prove the Whistle caller concept. The Whistle caller concept is based on the fact that dolphins occasionally use other dolphins’ signature whistles in order to address specific group members and convene.  Our hypotheses were that (1) dolphins call-over trained using their SW would learn the behaviour faster than dolphins trained using TSs, and (2) dolphins trained with their SW would be able to discriminate between different SWs better than dolphins trained with a TS would be at discriminating between different TSs.  Three out of three dolphins were successfully call-over trained using their SW, and two out of three dolphins using their assigned TS. When discriminating between different sounds, two of the dolphins trained using their SW performed significantly better than one of the dolphins trained using a TS. However, there were large intra-group differences in the results, indicating that we cannot eliminate the possibility that these results stem from individual differences in these dolphins’ ability to learn new behaviours overall, rather than an understanding of the sounds they heard. We suggest that future studies focus on (1) male-female differences in discrimination success when applying the Whistle caller concept, (2) how the characteristics of the trivial sounds affect discrimination success, and (3) the option of calling more than one animal at a time by sending out several SWs in succession.

The Umwelt concept of Jakob von Uexküll considers animals as subjects that inhabit their own subjective universe which is determined by the animal's sensory perception and cognitive abilities. Dolphins present an interesting species to investigate its Umwelt because cetaceans underwent a drastic change in lifestyle in the course of evolution because these mammals returned from a terrestrial life back into the water. Although bottlenose dolphins are intensively studied there are still many knowledge gaps. Here we studied some aspects of the dolphins' Umwelt by asking: (1) how their nocturnal acoustic Umwelt is arranged; (2) what the production of vocal copies can tell us about the dolphins' perception of their environment; (3) whether they are able to perceive tastes (4) or odours; (5) whether they are sensitive to magnetic stimuli. We found that the dolphins' nocturnal Umwelt was characterized by a temporally patterned vocal activity that also included vocal copies of sounds that the dolphins had heard during the day. This is a striking separation between auditory memory formation and vocal copy production and the copies might be a vocally expressed nocturnal rehearsal of day events. Thus, vocalizations can serve as possible indicators of events or objects that are meaningful to the dolphins. Regarding dolphins' perceptive abilities, we found that they were sensitive to both gustatory and olfactory food-related stimuli. They might use this ability to locate and/or evaluate prey. Further, dolphins responded to a magnetic stimulus, suggesting that they are magnetosensitive, what could be useful for navigation. So far, chemo- and magnetoreception have not been considered seriously as potentially functional in dolphins. The results obtained during this thesis fill some of the gaps that still exist in the knowledge of the dolphin's Umwelt and therefore contribute to a better understanding of this species. Moreover, they illustrate that even already intensively studied species may still hold important facets of their biology to reveal and that research should broaden the view and remain unbiased when studying a topic.