Male Dolphins Research Articles

Affiliation history and age similarity predict alliance formation in adult male bottlenose dolphins.

Male alliances are an intriguing phenomenon in the context of reproduction since, in most taxa, males compete over an indivisible resource, female fertilization. Adult male bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia, form long-term, multilevel alliances to sequester estrus females. These alliances are therefore critical to male reproductive success. Yet, the long-term processes leading to the formation of such complex social bonds are still poorly understood. To identify the criteria by which male dolphins form social bonds with other males, we adopted a long-term approach by investigating the ontogeny of alliance formation. We followed the individual careers of 59 males for 14 years while they transitioned from adolescence (8-14 years of age) to adulthood (15-21 years old). Analyzing their genetic relationships and social associations in both age groups, we found that the vast majority of social bonds present in adolescence persisted through time. Male associations in early life predict alliance partners as adults. Kinship patterns explained associations during adolescence but not during adulthood. Instead, adult males associated with males of similar age. Our findings suggest that social bonds among peers, rather than kinship, play a central role in the development of adult male polyadic cooperation in dolphins.

Male aggression varies with consortship rate and habitat in a dolphin social network

Coalitions and alliances exemplify the core elements of conflict and cooperation in animal societies. Ecological influences on alliance formation are more readily attributed to within-species variation where phylogenetic signals are muted. Remarkably, male Indo-Pacific bottlenose dolphins in Shark Bay, Western Australia, exhibit systematic spatial variation in alliance behavior, not simply within a species or population, but within a single social network. Moving SE-NW along Peron Peninsula in Shark Bay, males ally more often in trios than pairs, consort females more often, and exhibit greater seasonal movements. Ecological models predict more male-male conflict in the north, but sufficient observations of aggression are lacking. However, dolphins often incur marks, in the form of tooth rakes, during conflicts. Here we report that the incidence of new tooth rake marks varies systematically in the predicted pattern, with greater marking in the north, where males form more trios and consort females at a higher rate. While our previous work demonstrated that alliance complexity has an ecological component, we can now infer that ecological variation impacts the level of alliance-related conflict in Shark Bay. To understand ecological influences on animal societies, researchers have focused on differences within species, where confounds due to evolutionary history are minimized. Such differences are usually found among geographically separated populations, but in Shark Bay, Western Australia, male dolphin alliance size and access to females increase along a spatial axis within a single social network. Here we report that aggression levels, evidenced by tooth rake marks, increase along the same axis. Alliances are of particular interest as they represent a complex kind of relationship, often implicated in the evolution of social intelligence. Our discovery of spatial variation in alliance behavior and aggression within a social network provides a unique opportunity to investigate the intersection of cognition, social structure, and ecology.

Influence of artisanal fisheries on the behaviour and social structure ofTursiops truncatusin the South-western Gulf of Mexico

AbstractBehavioural plasticity in animals is tested whenever competitive interactions for space and/or food resources occur between wildlife and human activities. This study uses the concepts of operational and non-operational interactions between bottlenose dolphins (Tursiops truncatus) and artisanal fisheries in Alvarado, to search for differences in behaviour, age structure and group size. We conducted 20 surveys between 2015 and 2016, and recorded 64 groups by means of scan sampling from either a research boat or a fixed vantage point. Average dolphin group size was small (${\bar{\rm x}}$= 3.2, SD = 2.2 individuals) and fewer individuals were commonly present when interaction with fisheries occurred. Operational interactions were defined within the first 30 m and occurred mainly with lone individuals (54% recorded from the lighthouse and 82% during surveys); this benchmark also accounted for higher frequencies in locomotion and feeding (χ2= 83.10; df = 7;P< 0.001). We found a higher rate of new behavioural events for dolphin groups furthest from human activities, as well as a decrease in behaviours that imply greater body exposure as dolphins approach the fishing spots. Age structure and dolphin group size were not different during and in the absence of interaction with fisheries, but most interactions involved male dolphins. Behavioural variations in the dolphins' repertoire are likely a strategy to reduce the risk of injuries or death when interacting with human activities; these dolphins seem to have habituated to or at least tolerate fishing activities within the study area, possibly constituting a sex-biased pressure.

Environment, endocrinology, and biochemistry influence expression of stress proteins in bottlenose dolphins

Natural and anthropogenic stressors have been reported to impact the health of marine mammals. Therefore, investigation of quantifiable biomarkers in response to stressors is required. We hypothesized that stress protein expression would be associated with biological and health variables in wild and managed-care bottlenose dolphins (Tursiops truncatus). To test this hypothesis, our study objectives were to (1) determine if stress proteins in skin, white blood cells (WBCs), and plasma could be measured with an antibody-based microarray, (2) measure stress-protein expression relative to biological data (location, sex, age, environment), and (3) determine if stress-protein expression was associated with endocrine, hematological, biochemical and serological variables and gene expression in bottlenose dolphins. Samples were collected from two wild groups (n = 28) and two managed-care groups (n = 17). Proteins involved in the HPA axis, apoptosis, proteotoxicity, and inflammation were identified as stress proteins. The expression of 3 out of 33 proteins was significantly (P < 0.05) greater in skin than plasma and WBCs. Male dolphins had significantly greater expression levels for 10 proteins in skin compared to females. The greatest number of stress-associated proteins varied by the dolphins' environment; nine were greater in managed-care dolphins and 15 were greater in wild dolphins, which may be related to wild dolphin disease status. Protein expression in skin and WBCs showed many positive relationships with measures of plasma endocrinology and biochemistry. This study provides further understanding of the underlying mechanisms of the stress response in bottlenose dolphins and application of a combination of novel methods to measure stress in wildlife.

Vocal behaviour of allied male dolphins during cooperative mate guarding

Coercive mate guarding, where males use aggression to control female movements, is a form of sexual coercion which functions to constrain female mate choice. Non-human primates, for example, herd females to keep them away from competing males, but male bottlenose dolphins (Tursiops aduncus) also herd females to keep them close to their alliance partners. Indeed, pairs and trios of male dolphins work together to sequester single estrus females and defend them from competing alliances. Yet how males facilitate such coordination remains unknown. Here, we investigate the vocal behaviour of allied male bottlenose dolphins during the herding of individual females, examining how the production of whistles and ‘pops’ (a threat vocalisation) varied with behavioural state and inter-animal distances. Allied males produced both whistles and pops significantly more often and at higher rates during social interactions, though they differed in function. Whistle rates increased significantly when new individuals joined the consorting group, consistent with previous work showing that whistles are part of a greeting sequence for this species. Whistle matching also appeared to play a role in within-alliance coordination. Pop vocalisations increased significantly when the nearest male to the female changed, likely inducing the female to remain close as the males coordinate a guard switch. Building upon prior research examining female movements in response to pops, we show that males approach the female and current guard whilst popping, leading to a guard switch. Our results provide new insights into the use of vocal signals during cooperative mate guarding between allied male dolphins.

Fine‐scale sociality reveals female–male affiliations and absence of male alliances in bottlenose dolphins (Tursiops truncatus) in the Shannon Estuary, Ireland

AbstractKnowledge of social behavior at an individual level is central to our understanding of complex mammalian societies. In this study, we analyzed the fine‐scale sociality of wild bottlenose dolphins in the Shannon Estuary, Ireland, by examining associations between members of the whole population and between specific female and male dolphins. We carried out 51 boat‐based individual focal follows on 18 identifiable bottlenose dolphins over 90.8 hr (39 days) between 2014 and 2016. Additionally, we conducted 353 boat‐based surveys (with 607 sightings) between 2012 and 2015, and identified 121 distinct adult/juvenile dolphins. The mean group size of focal dolphin groups was 7.2 ± 4.1 (range = 1–20) and the mean fission‐fusion rate was 3.06 ± 1.35 changes/hr. The most frequent composition of within‐group affiliate pairs was female–male. Focal males spent more time with female nearest‐neighbors than male nearest‐neighbors (p = .013). Differences between female and male activity budgets were not strongly supported (p = .13). There was no evidence for male alliance formation in the Shannon Estuary population, and all of the known‐sex top‐ranked associates (7) of known males (n = 10) were females. This research reveals a distinct bottlenose dolphin society with female–male affiliations and an absence of male alliances.

Tool use and social homophily among male bottlenose dolphins.

Homophilous behaviour plays a central role in the formation of human friendships. Individuals form social ties with others that show similar phenotypic traits, independently of relatedness. Evidence of such homophily can be found in bottlenose dolphins ( Tursiops aduncus) in Shark Bay, Western Australia, where females that use marine sponges as foraging tools often associate with other females that use sponges. 'Sponging' is a socially learned, time-consuming behaviour, transmitted from mother to calf. Previous research illustrated a strong female bias in adopting this technique. The lower propensity for males to engage in sponging may be due to its incompatibility with adult male-specific behaviours, particularly the formation of multi-level alliances. However, the link between sponging and male behaviour has never been formally tested. Here, we show that male spongers associated significantly more often with other male spongers irrespective of their level of relatedness. Male spongers spent significantly more time foraging, and less time resting and travelling, than did male non-spongers. Interestingly, we found no difference in time spent socializing. Our study provides novel insights into the relationship between tool use and activity budgets of male dolphins, and indicates social homophily in the second-order alliance composition of tool-using bottlenose dolphins.

Remote blubber sampling paired with liquid chromatography tandem mass spectrometry for steroidal endocrinology in free-ranging bottlenose dolphins (Tursiops truncatus)

Liquid chromatography tandem mass spectrometry allows for the measurement of steroid hormone suites in the blubber of marine mammals. By combining this technology with minimally invasive techniques such as remote biopsy, endocrine profiles can be assessed, allowing for studies of hormonal profile variation over time. In this study, we explored associations among different steroidogenic pathways and seasonal differences in blubber hormone profiles of free-ranging common bottlenose dolphins along the coast of South Carolina, USA. Male dolphins experience a peak in testosterone, androstenedione, progesterone, and 17-hydroxyprogesterone in the spring, likely related to an upregulation of the androgen steroidogenic pathway during mating season. We also observed increased cortisol concentrations during summer compared to winter. Among females, there was an increase in androstenedione with elevated progesterone concentrations indicative of pregnancy, highlighting another potential endocrine marker for pregnancy in free-ranging dolphins. This work emphasizes the importance of selecting the appropriate season for studies on endocrine status to effectively uncover physiological variation or disruption in free-ranging cetaceans.

Swimming Energy Economy in Bottlenose Dolphins Under Variable Drag Loading

Instrumenting animals with tags contributes additional resistive forces (weight, buoyancy, lift and drag) that may result in increased energetic costs; however, additional metabolic expense can be moderated by adjusting behaviour to maintain power output. We sought to increase hydrodynamic drag for near-surface swimming bottlenose dolphins, to investigate the metabolic effect of instrumentation. In this experiment, we investigate whether (1) metabolic rate increases systematically with hydrodynamic drag loading from tags of different sizes or (2) whether tagged individuals modulate speed, swimming distance and/or fluking motions under increased drag loading. We detected no significant difference in oxygen consumption rates when four male dolphins performed a repeated swimming task, but measured swimming speeds that were 34% (>1 m s-1) slower in the highest drag condition. To further investigate this observed response, we incrementally decreased and then increased drag in six loading conditions. When drag was reduced, dolphins increased swimming speed (+1.4 m s-1; +45%) and fluking frequency (+0.28 Hz; +16%). As drag was increased, swimming speed (-0.96 m s-1; -23%) and fluking frequency (-14 Hz; 7%) decreased again. Results from computational fluid dynamics simulations indicate that the experimentally observed changes in swimming speed would have maintained the level of external drag forces experienced by the animal. Together, these results indicate that dolphins may adjust swimming speed to modulate the drag force opposing their motion during swimming, adapting their behaviour to maintain a level of energy economy during locomotion.

Kinship influences social bonds among male southern Australian bottlenose dolphins (Tursiops cf. australis)

Male mammals employ a wide variety of mating strategies in order to increase their reproductive success, which in turn influence their social behavior. In some populations of bottlenose dolphins (Tursiops spp.), males cooperate in small groups or alliances to gain access to females for mating. However, the occurrence of these male cooperative groups has been predicted to occur only under certain social and ecological conditions, driven by factors such as differences in population density, operational sex ratio, and sexual size dimorphism. Here, we used generalized affiliation indices, social network techniques, and maternally and bi-parentally inherited genetic markers to investigate the affiliation patterns and genetic relatedness among male southern Australian bottlenose dolphins (Tursiops cf. australis) in a small embayment in South Australia. Photo-identification data and biopsy samples were collected in Coffin Bay from 2013 to 2015 through systematic boat-based surveys. We found that highly sighted male dolphins formed 12 social clusters composed of two to five individuals. Genetic analyses revealed that general male affiliation patterns were significantly correlated with mtDNA haplotype sharing. In addition, preferred affiliates showed significantly higher levels of genetic relatedness compared to casual and avoided male pairs. Our results corroborate theoretical expectations for the formation of social bonds in small delphinids and suggest that a high density of dolphins, with an expected skewed operational sex ratio and no apparent sexual size dimorphism, is likely to have favored the formation of strong male affiliations. In addition, the availability of genetic relatives within the population may have favored male affiliations based on kinship relationships. Male bottlenose dolphins use different strategies to gain access to females, from single roving individuals, pairs or trios in alliances, to stable mixed-sex groups. Moreover, the role of kinship in the formation of male social bonds also varies within and among populations. This variability has been attributed to differences in ecological and intrinsic factors. Here, we studied the affiliation patterns and genetic relatedness in southern Australian bottlenose dolphins and demonstrated that kinship plays an important role in the formation of close male social ties. Furthermore, the results corroborate previous findings about the factors that contribute to the formation of male social bonds in these animals.

Bottlenose Dolphins Retain Individual Vocal Labels in Multi-level Alliances

Cooperation between allied individuals and groupsis ubiquitous in human societies, and vocal communication is known to play a key role in facilitating such complex human behaviors [1, 2]. In fact, complex communication may be a feature of the kind of social cognition required for the formation of social alliances, facilitating both partner choice and the execution of coordinated behaviors [3]. As such, a compelling avenue for investigation is what role flexible communication systems play in the formation and maintenance of cooperative partnerships in other alliance-forming animals. Male bottlenose dolphins in some populations form complex multi-level alliances, where individuals cooperate in the pursuit and defense of an important resource: access to females [4]. These strong relationships can last for decades and are critical to each male's reproductive success [4]. Convergent vocal accommodation is used to signal social proximity to a partner or social group in many taxa [5, 6], and it has long been thought that allied male dolphins also converge onto a shared signal to broadcast alliance identity [5-8]. Here, we combine a decade of data on social interactions with dyadic relatedness estimates to show that male dolphins that form multi-level alliances in an open social network retain individual vocal labels that are distinct from those of their allies. Our results differ from earlier reports of signature whistle convergence among males that form stablealliance pairs. Instead, they suggest that individual vocal labels play a central role in the maintenance of differentiated relationships within complex nested alliances.

Potentially infanticidal behavior in the Amazon river dolphin (Inia geoffrensis)

Infanticide by males is a phenomenon common in species in which the reproductive output of large numbers of females can be monopolized by a small number of males. It is thought to increase a male’s fitness, at the expense of the fitness of the infant’s parents, by bringing females into season more quickly. Infanticide by males has been recorded in just three cetacean species. We report aggressive behavior suggestive of infanticide in a fourth, the Amazon river dolphin (Inia geoffrensis). We observed and photographed a series of attacks on a neonate Amazon river dolphin by a large male, with apparent protective behavior by the mother. Although infanticide was not confirmed, the forceful, aggressive behaviors were highly suggestive of infanticidal behavior and represent another important data point for comparative studies of infanticide in mammals. Amazon river dolphins may have a polygynous, polyandrous, or promiscuous mating system, the latter two of which are not the norm in species in which the reproductive output of large numbers of females are monopolized by a small number of males. However, sexual dimorphism, high rates of aggression by males, socio-sexual object-carrying displays by males, and a long interbirth interval suggest that successful male Amazon river dolphins may be able to monopolize a large proportion of mating opportunities, and it is plausible that male dolphins can improve their reproductive success by bringing females into estrous sooner by killing the offspring of other males.

Signal detection for identification energy and behaviour of male dolphin bottle nose (Tursiopsaduncus) using NTD Model

Noisy Time Domain (NTD) model and behaviour of male dolphin using the underwater camera, and also comparing between sound and time from the spectrum. Collecting data was taken at the Safari Park of Cisarua Bogor in Indonesia, in show pool. Data at the show with replications 1,2, and 3 has a salinity of 29 ‰. Sound whistle 3 is 28.03 dB with the frequency interval of 14.64 kHz-16 kHz. The results showed that salinity in the show pool with replication 1,2, and 3 has salinity value that is equal to 30 ‰. F-test at the show pool has heterogeneous value. Treat at the show pool has a value of P <0.001 and P <0.001. Noisy Time Domain have differences with each other and have a lot of different sound patterns and detection of energy from power spectral density (PSD) signal.

Whistle sound detection and behaviour of male dolphin bottle nose (Tursiops aduncus) using noisy time domain modelling in captivity

Whistle sound is a voice that is intended to echolocation, whistle sound is a major role in internal and inter-group communication. The objective research is to know the power spectral patterns and fluctuations in sound based on frequency of the sounds produced by dolphins and observing the position of dolphins. Noisy Time Domain (NTD) and behaviour using the underwater camera, and also comparing between time and sound spectrum. Data recording was taken at the Safari Park of Cisarua Bogor in Indonesia, by taking data in show pool. The results showed that salinity before feeding time in the show pool with replication 1,2, and 3 has salinity value that is equal to 30 ‰. Data at the show pool before feeding with replications 1,2, and 3 has a salinity of 29 ‰. Sound whistle 3 before feeding time of 28.03 dB with the frequency interval of 14 642 Hz-16000 Hz. F-test at the show pool before meals has heterogeneous value. Treat before meals at the show pool has a value of P <0.001 and P <0.001. Value Noisy Time Domain have differences with each other and have a lot of different sound patterns. In general, there are real differences are evidenced by F test on a range of time at each whistle on show pool in the time before meals. In general, there is a noticeable difference in the range of time at each whistle on show pool in the time before meals. The behaviour of dolphins have a habit that has the movement toward the surface of the pool and movement and position will be influenced frequency and intensity value.

Factor associated variations in the home range of a resident Adriatic common bottlenose dolphin population

This study investigates the influence of the most dominant factors (association patterns, gender, natal philopatry and anthropogenic pressure) on the home range size of the 44 most resident common bottlenose dolphins (Tursiops truncatus) inhabiting the waters of the Cres-Lošinj archipelago (north Adriatic Sea, Croatia), a recently declared NATURA 2000 SCI. Results show that variations in home range patterns (MCP, 95% KDE and 50% KDE home range size) among the individual resident dolphins are primarily related to differences in gender and reflect the way in which different genders respond to external stressors. In addition, results confirm the seasonal influence of nautical tourism on both female and male dolphins through changes in their home range sizes. The overall results improve current knowledge of the main anthropogenic threats that should be taken into consideration when developing conservation measures to be applied to this Cres and Lošinj SCI.

Effects of oral megestrol acetate administration on the hypothalamic-pituitary-adrenal axis of male bottlenose dolphins (Tursiops truncatus).

OBJECTIVE To evaluate the impact of oral megestrol acetate (MA) administration on adrenal function in male bottlenose dolphins (Tursiops truncatus). DESIGN Serial cross-sectional study. ANIMALS 8 adult male dolphins, all of which were receiving MA at various daily doses (range, 0 to 60 mg, PO) for the control of reproductive behavior. PROCEDURES Blood samples were collected every 2 weeks for 1 year from dolphins trained to voluntarily provide them. Cortisol, ACTH, and other hormone concentrations were measured in serum or plasma via radioimmunoassay or ELISA. Fecal samples, also provided by dolphins voluntarily, were assayed for glucocorticoid metabolite concentrations. Effects of daily MA dose on hormone concentrations were evaluated. RESULTS Daily MA doses as low as 10 mg strongly suppressed cortisol secretion in nearly all dolphins, and except for a single measurement, no dolphin had measurable serum concentrations at doses ≥ 20 mg. Variations in serum cortisol concentration were unrelated to season but were directly related to ACTH concentrations, suggesting primary effects upstream of the adrenal gland. Cessation of MA administration resulted in almost immediate restoration of measurable serum cortisol concentrations, although concentrations continued to rise in a few dolphins over the following weeks to months. CONCLUSIONS AND CLINICAL RELEVANCE Caution should be exercised when administering MA to control reproductive behavior in male dolphins. Because the hypothalamic-pituitary-adrenal axis appeared to be sensitive to even small doses of MA in dolphins, duration of treatment may be the most critical consideration.

Behaviour and Bioacoustic Characteristic of Male Dolphins Bottle Nose (Tursiops Aduncus) in Captive, Indonesia

Behaviour and Bioacoustic Characteristic of Male Dolphins Bottle Nose (Tursiops Aduncus) in Captive, Indonesia

Preliminary Report of Object Carrying Behavior by Provisioned Wild Australian Humpback Dolphins (Sousa sahulensis) in Tin Can Bay, Queensland, Australia

Object use by cetaceans is associated with complex cognitive processes, social relations, play and tool use. A comparative approach of how cetacean species use objects will increase our understanding of how this behavior evolved. This study reports on observations of object use by a small group of wild, provisioned Australian humpback dolphins (Sousa sahulensis) in Tin Can Bay, Australia. Data were collated from attendance records, interviews and photographs revealing 23 separate occasions of object use over seven years. A variety of objects, biological and artificial were used by male dolphins during social and play interactions often directed at people. Comparable interactions have occurred in another provisioning program suggesting the behavior may be unique to these situations. The behavior observed in the current study also indicates variations of object use within the species, as objects were not associated with foraging as has been reported in the literature.

Bioacoustic Characteristic Click Sound and Behaviour of Male Dolphins Bottle Nose (Tursiops aduncus)

We Dicsuss the problem of bioacoustics research, Bioacoustic is the science that combines biology and acoustics which refers on the production of sound, dispersion and reseption animals and humans. This study using acoustic and behavioral observations of dolphins by using passive acoustic science (bioacoustic) to see the difference pattern of sound, and treatment given in this study is a before and after eating at Safari Park Indonesia, Cisarua Bogor. Sound dolphins have the lowest intensity value of 28.03 dB and highest is 32.01 dB. Parameter salinity 30 ppm and temperature of 23°C with a pool depth of 4.4 meters. Range frequency the highest is 14.000-16.000 Hz and intensity the highest 23 dB at the first day after meal a click sound. Differences in sound intensity values before and after eating is the highest value of a click on the second day with the highest intensity was 32.01 dB and lowest before eating.

Bioacoustic Spectral Whistle Sound and Behaviour of Male Dolphin Bottle Nose (Tursiops aduncus) at Safari Park Indonesia, Cisarua Bogor

Whistle sound is generally used for echolocation purposes, while the sound of the blast-beat and whistles play a major role in internal and inter-group communication. The purpose of this research is to know the power spectral patterns and fluctuations in sound based on frequency and Power Spectral Density (PSD) of the sounds produced by dolphins and observing the position of dolphins, Noisy Time Domain (NTD) and behavior using underwater camera, and also comparing between time and sound spectrum. Data recording was taken at the Safari Park of Cisarua Bogor in Indonesia, by taking data in show pool and show pool. The results showed that salinity before feeding time in the show pool with replication 1,2, and 3 has salinity value that is equal to 30%. Data at the show pool before feeding with replications 1,2, and 3 has a salinity of 29%. Power Spectral Density (PSD) of the whistle sound before feeding was different from one another, but it has the same frequency range. The highest intensity values is at sound whistle 3 before feeding time at the show pool with an intensity value of 28.03 dB/Hz with frequency interval of 14642-16000 Hz. F-test at the show pool before meals has heterogeneous value. Treat before meals at the show pool has a value of P < 0.001 and P < 0.001. Value Noisy Time Domain has differences with each other and has a lot of different sound patterns. In general, there are real differences are evidenced by F test on a range of time at each whistle on physiotherapy and swimming pool show in the time before meals. The position of dolphins in a pool show more dominant and often in the bottom of the pool, the position of the dolphins affects the frequency.