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Establishing trust: Socio-sexual behaviour and the development of male-male bonds among Indian Ocean bottlenose dolphins
... Mammalian social play peaks during the juvenile period between weaning and sexual maturity (7,14), and juvenile social play often resembles aggressive and sexual behaviors that are important for adult reproduction (7,(14)(15)(16)(17)(18)(19)(20). In light of this, it has long been hypothesized that juvenile social play functions as practice of important adult behaviors such as sex, aggressive contests over mates, sexual displays, and mate guarding (8,21). ...
... A prominent feature of social play in this population is play herding, where juveniles take turns in adult male (actor) and female (receiver) mating roles (40). These play herding events resemble consortships because they involve sociosexual behavior that is frequently directed jointly by two or more individuals (the actors) toward another (the receiver) (16,41). However, this behavior is clearly distinguishable as play. ...
... Unlike in adult consortships, play herding only occurs in a social context and ceases when animals begin to rest, forage, or travel (40). Furthermore, play groups are often single-sex and, in mixed-sex play groups, individuals of both sexes take turns in each role (16,40). Thus, social play in this population may provide juveniles of both sexes with the opportunity to practice important mating skills, i.e., the practice hypothesis. ...
For over a century, the evolution of animal play has sparked scientific curiosity. The prevalence of social play in juvenile mammals suggests that play is a beneficial behavior, potentially contributing to individual fitness. Yet evidence from wild animals supporting the long-hypothesized link between juvenile social play, adult behavior, and fitness remains limited. In Western Australia, adult male bottlenose dolphins ( Tursiops aduncus ) form multilevel alliances that are crucial for their reproductive success. A key adult mating behavior involves allied males using joint action to herd individual females. Juveniles of both sexes invest significant time in play that resembles adult herding—taking turns in mature male (actor) and female (receiver) roles. Using a 32-y dataset of individual-level association patterns, paternity success, and behavioral observations, we show that juvenile males with stronger social bonds are significantly more likely to engage in joint action when play-herding in actor roles. Juvenile males also monopolized the actor role and produced an adult male herding vocalization (“pops”) when playing with females. Notably, males who spent more time playing in the actor role as juveniles achieved more paternities as adults. These findings not only reveal that play behavior provides male dolphins with mating skill practice years before they sexually mature but also demonstrate in a wild animal population that juvenile social play predicts adult reproductive success.
... Like affiliative behaviour, sexual behaviour in dolphin societies has been suggested to maintain social dynamics, bonding, and group cohesion ( [116,117]; for a review see, Manitzas Hill et al. [118]). Socio-sexual behaviour is defined through opposite and samesex genital contact and includes mounting, goosing, push-ups, petting, and rubbing of the genital area (see Harvey et al. [119] and Mann [117]). ...
... Like affiliative behaviour, sexual behaviour in dolphin societies has been suggested to maintain social dynamics, bonding, and group cohesion ( [116,117]; for a review see, Manitzas Hill et al. [118]). Socio-sexual behaviour is defined through opposite and samesex genital contact and includes mounting, goosing, push-ups, petting, and rubbing of the genital area (see Harvey et al. [119] and Mann [117]). Again, the scoring is based on the presence or absence of this behaviour, with the presence indicating an adequate welfare state (score of 0) and the absence indicating an inadequate welfare state (score of 2). ...
Ensuring high standards of animal welfare is not only an ethical duty for zoos and aquariums, but it is also essential to achieve their conservation, education, and research goals. While for some species, animal welfare assessment frameworks are already in place, little has been done for marine animals under human care. Responding to this demand, the welfare committee of the European Association for Aquatic Mammals (EAAM) set up a group of experts on welfare science, cetacean biology, and zoo animal medicine across Europe. Their objective was to develop a comprehensive tool to evaluate the welfare of bottlenose dolphins (Tursiops truncatus), named Dolphin-WET. The tool encompasses 49 indicators that were either validated through peer review or management-based expertise. The first of its kind, the Dolphin-WET is a species-specific welfare assessment tool that provides a holistic approach to evaluating dolphin welfare. Inspired by Mellor’s Five Domains Model and the Welfare Quality®, its hierarchical structure allows for detailed assessments from overall welfare down to specific indicators. Through combining 37 animal-based and 12 resource-based indicators that are evaluated based on a two- or three-level scoring, the protocol offers a detailed evaluation of individual dolphins. This approach allows for regular internal monitoring and targeted welfare management, enabling caretakers to address specific welfare concerns effectively.
... For example, same-sex sexual behaviour seems to facilitate reconciliation among group members in female bonobos (Pan paniscus) 27 and female Japanese macaques (Macaca fuscata) 28 . Similarly, same-sex sexual behaviour seems to serve to reinforce the alliance between small groups of male bottlenose dolphins (Tursiops spp.) 29 , whereas it helps to strengthen dominance hierarchies in herds of American bison (Bison bison) 30 . Despite the value of these studies for inferring the reasons why same-sex sexual behaviour manifests in particular species, a deeper understanding of how this sexual behaviour has evolved requires thorough testing of the adaptive hypotheses in a broader phylogenetic context 4,14-16 . ...
... For example, same-sex sexual behaviour appears to be more common in social nonhuman primates forming multi-male/multi-female groups than in monogamous and polygynous species 7 . Likewise, same-sex sexual behaviour seems to facilitate reconciliation among group members in female bonobos (Pan paniscus) 27 and female Japanese macaques (Macaca fuscata) 28 , to strengthen alliance between small groups of male bottlenose dolphins (Tursiops spp.) 29 , and to help to reinforce dominance hierarchies in herds of American bison (Bison bison) 30 . In addition, it seems that the contingent evolution of same-sex sexual behaviour on sociality observed in mammals may also occur in other animal groups, such as male birds 44 . ...
Same-sex sexual behaviour has attracted the attention of many scientists working in disparate areas, from sociology and psychology to behavioural and evolutionary biology. Since it does not contribute directly to reproduction, same-sex sexual behaviour is considered an evolutionary conundrum. Here, using phylogenetic analyses, we explore the evolution of same-sex sexual behaviour in mammals. According to currently available data, this behaviour is not randomly distributed across mammal lineages, but tends to be particularly prevalent in some clades, especially primates. Ancestral reconstruction suggests that same-sex sexual behaviour may have evolved multiple times, with its appearance being a recent phenomenon in most mammalian lineages. Our phylogenetically informed analyses testing for associations between same-sex sexual behaviour and other species characteristics suggest that it may play an adaptive role in maintaining social relationships and mitigating conflict.
... 36,41 The mother is the first playmate and then the calf expands its social network and starts playing with other conspecifics, preferring unrelated companions of similar age. [41][42][43][44] Despite the human perception of their ''anatomical smile'' as a friendly feature, 45 the role of facial communication in managing playful encounters remains unexplored in dolphins, although there is evidence that they rely on the visual sensory modality in their social life. [46][47][48][49] Here, by recording the free activities (outside the training and feeding sessions) of captive bottlenose dolphins, we explore the presence and possible functions of open mouth display (OM) during solitary, interspecific (human-dolphin), and intraspecific free play (spontaneously evoked according to the second Burghardt's criterion, 9 ) by testing the following hypotheses. ...
Play is a widespread behavior present in phylogenetically distant taxa that, in its social form, relies on com- plex communication. Playful communication has been largely neglected in marine mammals. We focus on playful visual communication in bottlenose dolphins. The open mouth (OM) display was mainly emitted during social than during solitary play and occurred more frequently when the sender was in the receiver’s field of view, suggesting that animals are attentive to the playmate’s attentional state. Detecting an OM evoked the same facial display in the receiver, a result that strikingly matches with those obtained on cooperative social primates and carnivores. It is difficult to know whether such similarities derive from shared evolutionary pathways (homology) or from evolutionary convergence (homoplasy), as both have been suggested for play behavior. The pervasive presence of OM and rapid mimicry in the mammal phylo- genetic tree indicates the relevance of visual mechanisms in shaping complex communication.
... In rhesus monkeys (Macaca mulatta) and Japanese monkeys (Macaca fuscata), mounting among males may serve as a socially cohesive behavior by facilitating nonagonistic contact (Reinhardt et al. 1986;Hanby 1974), which is thought to serve as "social glue". In Indian Ocean bottlenose dolphin calves (Tursiops aduncus), pseudo-sexual behavior between males plays an important role in the formation and maintenance of male bonds (Mann 2006). In sh species such as guppies (Poecilia reticulata), the absence of females induces inter-male pseudo-sexual behavior under laboratory conditions (Field and Waite 2004). ...
Aggressive behavior, exhibiting a unidirectional behavioral event across various animal species, is instrumental in fortifying the existing hierarchical order and maintaining social stability within the group. In the present study, we investigated the types of aggressive behavior exhibiting unidirectional properties that function as dominance signals among three male medaka fish ( Oryzias latipes ). We first examined the directionality of attack/bite and chase behaviors, revealing that males often exhibited bidirectional physical attacks, while demonstrating predominantly unidirectional chasing behavior. This directionality was maintained throughout the hierarchy formation. Upon observing that male medaka fish exhibit courtship-like displays during male-male interactions, we subsequently investigated the timing and directionality of attack/bite, chasing, and courtship-like displays. Males exhibited unidirectional courtship-like displays, with the directionality matching that of chasing behavior. In addition, the number of attack/bite behaviors significantly decreased after the first chasing as well as the first courtship-like displays. Taken together, our findings strongly suggest that chasing and courtship-like displays may function as dominance signals, reinforcing established dominance-subordinate relationships. Furthermore, when the three males were separated for half a day and then reunited the following day, the number of physical attacks decreased significantly, while the directionality of chasing behavior and courtship-like displays remained unchanged. This finding suggests that once a dominance-subordinate relationship is established, it can be maintained through chasing behavior and courtship-like displays. These observations provide insight into how unilateral pseudo-sexual behavior between males can influence hierarchy formation in social animals.
... 15 Even while Gómez et al. (2023) coded nearly all mammal species exhibiting SSB as being adult-centered in the SSB, they nevertheless showcased two and only two species-specific research studies, in which male SSB was prominent, to illustrate SSB's proposed functions, but in which the male SSB was mostly or exclusively non-adult centered in both behavior and function. These studies were on bottlenose dolphins (Torsiops sp.), in which the great majority of SSB was performed by male calves and juveniles (Mann, 2006), and on American bison (Bison bison), in which the great majority of SSB was performed by male juveniles and adolescents (Vervaecke & Roden, 2006; see also Bagemihl, 1999;Rothstein & Griswold, 1991). Gómez et al.'s coding placed these species as adult-centered SSB. ...
In the present study, relations between same-sex sexual behavior (SSB), age-class, and coalitional behavior in male rhesus macaques were examined in a re-analysis of data first analyzed and reported by Clive et al. (2023). Age-class as a focal variable was indicated in an extensive literature review, which showed that male non-adult (juvenile, adolescent) participation in SSB is extensive in this and related primate species and associated with various benefits. Clive et al. (2023) excluded juveniles from their analysis. In the re-analysis (n = 995 mounting events), it was found that non-adult involvement was substantial (51%). Most dyads contained at least one non-adult (76%). Young and prime adult mounters most often selected non-adults to mount. Mounters were often sexually motivated: most for adolescents (72%); equally for juveniles (57%) and adults (56%). Finally, the highest rate of SSB with coalitional context appeared in adolescent–adult dyads involved in multiple repeated mounts. SSB, age-class, special friendships, bonding, and coalitions were linked, as reported in some other primate species and human societies cross-culturally. Employing age-class in male SSB analysis improved description and explanation.
... The purpose for nonreproductive behavior is varied; proposed functions include learning or practicing reproductive behaviors, establishing or reinforcing dominance relationships, forming social alliances, and/or reduction in social tension (reviewed in Bagemihl, 1999;Bailey & Zuk, 2009). Male-male sexual behavior is well studied in common bottlenose dolphins and plays an important role in social interactions among individuals (Caldwell & Caldwell, 1972;Mann, 2006;Östman, 1991). Nonsexual behavior in cetaceans can also be associated with agonism and dominance behavior (Ham et al., 2023). ...
Humpback whales (Megaptera novaeangliae) are a species whose social behavior has been studied for decades, but whose sexual behavior remains largely undescribed. Most humpback whales spend the summer months feeding in polar waters and migrate during fall and winter months to tropical waters, where the observed behaviors are related largely to reproduction (Chittleborough, 1965; Craig et al., 2003; Currie et al., 2018). Despite decades of research on humpback whales around the world, reports of penis extrusion by males are relatively rare (Herman et al., 2007; Pack et al., 1998, 2002) and copulation in humpback whales has not yet been documented (Ransome et al., 2021). This is the first report of penetration by a humpback whale, and the first report of sexual activity between two male humpback whales. Nonreproductive sexual behavior occurs between individuals whose age and/or sex mean that there is no possibility of producing offspring, such as same sex interactions or interactions between immature animals (Furuichi et al., 2014). In many species, the functions of sexual behavior extend beyond reproduction. Heterosexual behavior often occurs in nonreproductive contexts and homosexual behavior is common in the animal kingdom (Bagemihl, 1999). Sexual interactions between individuals of the same sex have been documented for a wide range of species, as reviewed in Bagemihl (1999). Among marine mammals, there are observations of this behavior in pinnipeds, e.g. robustus; and bowhead whale, Balaena mysticetus (reviewed in Bagemihl, 1999; Ham et al., 2023). In male cetaceans, homosexual activity can involve insertion of the penis of one male into the genital slit (Sylvestre, 1985) or anus (Renjun et al., 1994) of another male. The purpose for nonreproductive behavior is varied; proposed functions include learning or practicing reproductive behaviors, establishing or reinforcing dominance relationships, forming
... Male common bottlenose dolphins were observed mounting male Atlantic spotted dolphins; however, male spotted dolphins were not observed mounting male common bottlenose dolphins in mixed-species groups . Additional field studies of homosexual behavior among Indo-Pacific bottlenose dolphins have noted higher levels and longer duration of socio-sexual behavior among male-male pairs of dolphins than among male-female and female-female pairs (Mann 2006). Homosexual behaviors have also been reported among sexually mature bowhead whales (Würsig and Clark 1993) and among sexually mature and immature southern right whales (Eubalaena australis; Sironi 2004). ...
We provide a conceptual primer for sexual selection and conflict, mating systems, and socio-sexual behaviors and patterns among animals, largely with mammalian and cetacean examples. The important roles of mate choice are discussed (including female choice) and the occasional fluidity of sexual roles. An overview of topics pertinent to sex and behavior is described, including evolutionary drivers (the concept of “why sex after all?”) followed by general mammalian and cetacean mating strategies and tactics. We describe mating systems (monogamy, polygyny, polyandry, polygynandry) with the present understanding that most cetaceans do not have monogamous or polyandrous mating systems. The primer includes brief introductions to historical knowledge and highlights emerging areas of research within the field of sex in cetaceans, with context for other chapters of this book. As part of overall sexual behavior, alloparental care, female reproductive senescence, and non-procreative behaviors including homosexual and necrocoital mating are also introduced.
The development of non-invasive methods to study brain structure and function has enabled a flowering of cognitive neuroscience in humans and nonhuman species. Herein, we describe the development of protocols for functional magnetic resonance imaging (fMRI) of a bottlenose dolphin (Tursiops truncatus), including protocols to monitor the health and welfare of the subject over the course of our five-year study. A Welfare Control Plan (WCP) was designed to monitor, enhance, and protect our subject’s welfare throughout the course of the study. The WCP was developed so our team of marine mammal veterinarians, trainers, and researchers could (1) identify study procedures that might negatively impact the individual’s welfare and propose measures to mitigate them, (2) define and implement protocols for monitoring the individual’s welfare throughout the study, and (3) determine the study’s temporary or final endpoints. Overall, behavioral, physiological, and health welfare indicators showed that the dolphin’s quality of life was not negatively impacted by participating in our functional neuroimaging study. Our study provides an example of how innovative, ambitious, and logistically complex animal studies can successfully be performed while protecting the welfare of participating animals through adequate planning, enough human and economic resources, and full human/institutional commitment to animal welfare.
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