The Amazon river dolphins study reveals an unusual airborne urine display that might play a social role among males. Over four years in central Brazil, researchers observed a surprising pattern: male river dolphins routinely turned onto their backs, presented their genitalia, and sprayed urine into the air, sometimes reaching about three feet high. These displays often occurred when other males were nearby, drawing curiosity and even pursuit from nearby dolphins. The findings suggest a potential form of chemical or acoustic communication rather than a simple, routine bodily function, and they challenge assumptions about how these freshwater dolphins signal with one another. The observations come from a long-running field effort conducted between 2014 and 2018 along the Tocantins River, during which researchers recorded hundreds of hours of dolphin activity and cataloged numerous instances of this aerial urination behavior. Alongside the core discovery, the researchers note that the behavior was more commonly observed than expected, involving multiple individuals in many cases and lasting only a brief period but sometimes drawing attention from several nearby dolphins. The study’s co-author, Claryana Araújo-Wang, emphasized that the team was both surprised and intrigued by the breadth of this behavior, which had never been documented in such a clear, systematic way. This article revisits the observed pattern, explores possible explanations, and situates the behavior within broader discussions of cetacean communication and social dynamics.
Folklore and the spark of scientific curiosity
Across Amazonian folklore, stories about river dolphins—known locally as bufeos or boto—often portray them as shapeshifters that can transform at night into handsome men who lure human women. These legends echo in other cultures where dolphins appear in myths as boundary-crossing beings capable of extraordinary acts. The roots of such tales may lie, in part, in the dolphins’ anatomy, which can appear strikingly human-like to observers unfamiliar with aquatic life. While the folklore embodies cultural imagination, it also frames a compelling scientific question: do these dolphins use social signals that might, at least in part, resemble human ceremonial displays?
From the field, researchers focused on a different kind of spectacle—behavior that could illuminate how male dolphins communicate and negotiate social relationships. Over four years, a team in central Brazil documented 36 distinct cases in which adult male Amazon river dolphins displayed their genitalia and released a jet of urine into the air. The pattern emerged during periods when other males were nearby, suggesting the behavior functions within a social arena rather than serving a purely physiological purpose. The collective observations point toward an intentional display rather than incidental urination. The researchers describe the behavior as a potential form of chemical sensory communication, possibly signaling health, dominance, or readiness to engage in social competition. The unusual nature of the behavior prompted the team to interpret it as more than a mere reflex, inviting broader speculation about how cetaceans convey information in a dense, riverine environment.
The interplay between folklore and empirical investigation proved fertile for understanding cetacean social life in freshwater habitats. Folklore can spark curiosity that translates into rigorous fieldwork, and this study demonstrates how cultural narratives may inadvertently cue scientists to look for overlooked forms of communication in non-mammal-dominated ecosystems. In this case, the long-standing curiosity about dolphin behavior intersected with a systematic inquiry into a striking display that had not previously been documented with such clarity. The objective shift—from myth-inspired wonder to data-driven interpretation—reflects a broader trend in animal behavior research, where unusual displays may encode complex messages about social status, territory, or mating strategies. The discovery thus sits at the crossroads of anthropology-inspired curiosity and ethology-driven analysis, offering both cultural context and scientific insight.
Aerial urination as a potential signal in the social theater
In the narrative of cetacean behavior, the aerial urine display stands out as a distinctive form of communication that blends visibility, timing, and social context. The researchers recorded a total of 36 documented instances in a natural riverine setting, each occurring amid groups or near nearby conspecifics. The display typically involved a male dolphin rolling onto his back while presenting his genitalia and releasing a spray that could reach several feet above the water’s surface. In many observed cases, the display did not occur in isolation; two-thirds of the incidents involved at least one other male dolphin positioned under or near the urine stream or within the path of the spray, suggesting an interactive component rather than a unidirectional emphasis on self-display.
The duration of each urination event tended to be brief, averaging about 11 seconds, with a range from a single second to as long as 41 seconds. Even though the act occasionally occurred with a solitary initiator, it more frequently occurred in a social frame where other males were present, watching, following, or seemingly engaging with the display. Such a pattern invites interpretation in terms of social signaling, where the sender communicates status, willingness to compete, or potential mating-related cues to nearby rivals or prospective mates. The combination of a visible physical display with an airborne urinary jet creates a distinctive sensory event that could be perceived through multiple channels, including visual, chemical, and possibly acoustic modalities.
While the study does not claim a definitive function for the behavior, it offers a carefully reasoned set of hypotheses. One possibility is chemical communication: although dolphins are not known for robust olfactory capabilities in water, there is evidence that they can detect some odorants and secretions airborne or dissolved in water. The researchers point to the taste-based identification of fellow dolphins through the urine of bottlenose dolphins as a possible analog, suggesting that urine may carry information recognizable to other dolphins, at least in certain contexts. Another plausible mechanism is acoustical signaling: the act of spraying urine into air and hitting water could generate acoustic cues or modulate existing soundscapes in ways that other dolphins hear and interpret. Alternatively, the behavior may reflect a more pragmatic or even playful motive—an aesthetic display that individuals enjoy, or a self-perceptual reminder of dominance—though the researchers stress that the observed frequency and context make purely recreational explanations unlikely to capture the full story.
The context of the Tocantins River, with its seasonal variations, dense riparian features, and diverse social groups, adds layers of complexity to interpretation. River environments expose cetaceans to distinct ecological pressures compared to offshore or estuarine habitats, including variable water quality, shifting prey availability, and dynamic social networks shaped by group composition and habitat use. In such settings, a conspicuous display like aerial urination could serve multiple functions that change with social context: marking territorial boundaries, signaling alliance or rival status within a pod, or conveying readiness to mate under particular ecological constraints. The field team’s long-term data collection—spanning nearly 219 hours of observed dolphin activity—provides a robust foundation for discussing these possibilities, while acknowledging that more work is needed to parse cause, effect, and fitness consequences.
Methods and field observations: how the data came together
The central Brazil study unfolded over a four-year window, with researchers conducting land-based surveys along the Tocantins River between 2014 and 2018. The field team accumulated a substantial observational dataset, recording almost 219 hours of dolphin activity and behavior. This longitudinal approach allowed researchers to capture a wide range of social interactions, environmental conditions, and group configurations, providing a richer context for understanding the aerial urination phenomenon than a short-term snapshot would have afforded.
During these surveys, researchers identified individual initiators—referred to as “urinators”—and tracked the presence and behavior of nearby dolphins, the “receivers,” who observed, followed, or positioned themselves under the spray. In many cases, the same individuals participated in multiple events across different days or weeks, offering a window into patterns of repetition and possible social recognition. The observational protocol emphasized consistency in recording context, including the number of animals present, approximate distance to the spray, the height and direction of the urine jet, duration of the event, and any subsequent social behaviors that followed the display. The researchers also documented accompanying movements, such as turning onto the back, arching the body, and lingering post-event positions, which could illuminate post-display social dynamics.
One notable finding—two-thirds of the observed urination events involved at least one other male dolphin acting as a receiver—points to the social salience of the display. In many instances, receivers stood directly beneath or in the path of the urine stream, suggesting potential attention capture, shared interest, or even a form of social investigation by conspecifics. This pattern strengthens the interpretation that the behavior serves a communicative purpose, rather than being solely a private physiological release. The fact that these events lasted on average about 11 seconds, with a broad range, further highlights the dynamic, time-bound nature of such social signaling events in a natural river environment.
The study design also included a comparative lens: researchers considered analogous behaviors in other aquatic species where urine exposure or chemical cues serve communicative roles. They noted that urine-scent or urine-related signaling has been documented in various taxa, including some fish and crustaceans, where urine discharges can convey information about territory, aggression, or mating readiness. While cetaceans rely heavily on sound and vision, the observed aerial urination raises questions about the extent to which chemical cues may contribute to social signaling in riverine dolphins. The researchers emphasize that their observations do not suggest conventional scent-based communication comparable to terrestrial mammals, but rather a nuanced, potentially multi-modal signaling system that merits further investigation with noninvasive methods such as hydroacoustic monitoring and urine analysis when feasible in protected, non-disruptive study contexts.
Methodological considerations are essential to interpret the results responsibly. The Tocantins River environment presents logistical challenges for continuous monitoring, including variable light conditions, fluctuating water levels, and seasonal shifts in dolphin distribution. The field team mitigated these constraints by distributing observation efforts across different times of day, weather conditions, and river reaches, to maximize representative sampling of social interactions. Nonetheless, the researchers acknowledge potential biases—such as observer attention being drawn to more dramatic displays, or the possibility that some events went undocumented due to distance or water turbidity. They also stress that the observed frequency of aerial urination may reflect the sampling intensity and the particular social structure of the populations studied rather than a universal pattern among all Amazon river dolphins. Despite these caveats, the data set remains a substantial contribution, revealing a consistent, recurrent behavior with clear social context and measurable temporal characteristics.
In presenting their findings, the researchers avoided over-claiming causal functions. Instead, they offered plausible hypotheses grounded in observed patterns and comparative biology and encouraged further research to test these ideas with increasingly precise methods. The study’s approach—documenting spontaneous, context-rich social displays over an extended period in a natural habitat—helps ensure that the observed behavior reflects genuine aspects of dolphin social life rather than researcher-driven or laboratory-specific phenomena. The overall picture is one of careful, descriptive ethology that invites hypothesis-driven follow-up studies while maintaining a strong emphasis on non-invasive observation and ecological validity.
Data nuances and analytical angles
Within the broader data landscape, several key patterns stood out. The average duration of an aerial urination event—about 11 seconds—offers a window into the tempo of social signaling in this context. The range, from a single-second event to one lasting 41 seconds, highlights variability that could correspond to different social intentions or levels of audience engagement. The fact that most events involved multiple receivers suggests that the display may function as a broadcast signal designed to reach a broader subset of the social network rather than a private message between two individuals.
The height of the urine plume, reported as high as three feet in air, raises questions about how such a display is perceivable by nearby dolphins. Visual salience is one potential channel, but given the aquatic environment, other modalities could play a role as well. For instance, the spray could alter the local acoustic environment by generating brief water-jet sounds, or it might introduce odorants that nearby dolphins detect through gustation or taste cues, as observed in other dolphin species. The presence of “receivers” directly beneath the stream in many instances could indicate a form of attention capture or social evaluation—an implicit audience effect where the initiator’s signal is tested or reinforced through audience response.
The research team’s reflections about possible mechanisms also consider the sensory biology of dolphins. Although dolphins are renowned for their sophisticated sonar and auditory capabilities, their olfactory sense is less prominent in the aquatic environment. However, there is evidence that cetaceans can detect certain odorants and secretions in both air and water, suggesting that airborne urine may carry detectable cues under the right conditions. The idea that the urine serves not only as a chemical message but also as a multi-sensory signal—interacting with sky, water, and air vibrations—presents a compelling hypothesis for organismal communication in a river system where visibility and acoustic channels interact dynamically.
In addition to chemical and acoustic hypotheses, researchers consider behavioral and social dynamics. The fact that aerial urination often occurs in the presence of other males could reflect competition, status assertion, or signaling of body condition relevant to male-male competition or future mating opportunities. The precise social meanings behind any one event will likely vary with the individuals involved, their social histories, and the broader group context. The findings thus point toward a rich, context-dependent signaling system in which aerial urination is one component among a broader repertoire of social interactions that shape the bonds, hierarchies, and mating strategies of Amazon river dolphins.
The behavior in a broader cetacean and aquatic context
The observed aerial urination in Amazon river dolphins sits alongside a broader tapestry of signaling behaviors across aquatic species. Urine-related signaling is documented in a range of organisms and often serves functions such as territory marking, social acknowledgment, mate attraction, or threat display. In several terrestrial and aquatic systems, chemical signals carried by urine convey information about health, hormonal status, age, and social dominance. In some fish species, urinary discharge can be a deliberate social signal used in conjunction with visual displays, territory defense, or reproductive rituals. In crustaceans and other invertebrates with more accessible chemical signaling channels, urine may function as a cue that others use to modulate aggression, avoidance, or approach behavior.
For context, the study notes that in certain aquatic taxa, urine-based signaling has been associated with territorial marking or specific reproductive contexts. While these patterns should not be generalized to cetaceans without careful testing, they provide a useful comparative lens. In particular, certain fish and crustacean species exhibit heightened aggression or social recognition in response to urine cues, suggesting that urinary signaling can convey meaningful information in social networks even in environments where visibility is limited or where chemical cues disperse through water rather than air alone. The authors also discuss the possibility that airborne urine interacting with water surfaces could generate acoustic cues or physical ripples that other dolphins may notice, adding a potential cross-modal aspect to the signaling system.
A notable example cited by researchers involves African cichlids, where males emit pulses of urine to mark territory and communicate in reproductive contexts. Although the taxonomic and ecological contexts differ significantly, the comparative spark remains valuable: in diverse animal lineages, urine can serve as a social medium that complements visual or acoustic channels. In the narrow-closed crayfish, studies show that a marked decrease in male aggression occurs when a rival’s urine is detected, suggesting that urine carries information about both identity and aggressive propensity. These cross-species observations highlight a common logic in animal signaling: chemical cues, when integrated with other sensory information, can influence social decisions in ways that shape the structure and outcomes of communal life.
In light of these comparisons, the Amazon river dolphin case invites a careful, multi-faceted inquiry into how cetaceans may employ chemical or multi-modal cues in riverine environments. The researchers stress that aerial urination should be understood as a potential signal within a broader communicative toolkit rather than as a single, standalone act. The olfactory and gustatory dimensions of dolphin perception, the acoustic environment of river systems, and the social networks within pods collectively determine how such a signal is produced, perceived, and interpreted. The study thus contributes to a growing interest in the sensory ecology of cetaceans beyond traditional vocalization analyses, encouraging researchers to explore how dynamic riverine habitats influence the evolution and deployment of social signals.
Possible mechanisms: chemical, acoustic, and perceptual considerations
A central question concerns how dolphins might detect and interpret airborne urine in a habitat where scent cues are often diluted by water and wind. The authors note that while dolphins are not typically thought of as highly olfactory animals, they do possess sensory modalities that can respond to chemical cues in certain contexts. There is evidence suggesting that bottlenose dolphins can use taste to recognize individuals through the taste of a rival’s urine, indicating a nuanced chemosensory pathway that could extend to other dolphin species. If Amazon river dolphins similarly detect chemical cues from urine, the aerial plume could provide information about the donor’s identity, health status, or social standing, which others might use to guide their behavior in real time.
In addition to chemical signaling, acoustic consequences are plausible. The act of spraying urine into air can create small jets and splashes that produce brief acoustic signatures detectable by hearing dolphins nearby. Given the sensitivity of dolphins to a wide spectrum of sounds, even subtle water-jet noises and droplets striking the surface could be integrated into the audience’s perception of the display. The spatial arrangement of the receivers—often positioned beneath or close to the spray—could also influence how the signal is perceived, with differences in distance, orientation, and the surrounding vocal environment shaping the interpretive outcomes.
A further possibility is that the behavior reflects an intrinsic social activity that the dolphins find aesthetically appealing or phylogenetically favored in certain contexts. The combination of a striking visual display, potential chemical cues, and possible acoustic echoes could generate a multi-channel signal whose meaning emerges through social learning and individual recognition across repeated encounters. The researchers acknowledge that disentangling these mechanisms will require more targeted research, including non-invasive approaches to sampling urine composition, advanced hydroacoustic monitoring to capture any concurrent signals, and longitudinal tracking of individuals to assess whether particular signals correlate with observed fitness-related outcomes such as access to mates or dominance hierarchies.
Implications for understanding Amazon river dolphins and social complexity
The aerial urination observations add a new layer to our understanding of Amazon river dolphins, a species living in a high-variability freshwater system. The presence of such a display suggests that these dolphins possess a broader and more nuanced social repertoire than previously recognized, with potential implications for how social networks are formed, maintained, and navigated in riverine contexts. If aerial urination functions as a signal of dominance, breeding readiness, or social status, it could influence how individuals partition space, form alliances, or time their presence in particular riverine zones that offer foraging or mating opportunities.
From a conservation perspective, recognizing the social sophistication of these dolphins underscores the importance of protecting riverine habitats that support complex social systems. River ecosystems are subject to human-induced changes—pollution, dam construction, altered flow regimes—that can disrupt social structures and the cues animals rely upon for coordination and reproduction. Understanding the full spectrum of social signals helps researchers and policymakers appreciate the ecological value of preserving natural hydrological patterns and habitat connectivity. It also highlights the need for non-invasive, long-term monitoring strategies that prioritize animal welfare while yielding robust behavioral data.
The study’s findings reinforce the idea that dolphin social life, even in riverine habitats, involves layered communication that integrates multiple modalities. The interplay of visual displays, potential chemical cues, and auditory information can create a rich signaling milieu that supports group cohesion, mate competition, and territorial dynamics in fluctuating environments. By documenting a previously unrecorded behavior in a natural setting, researchers expand the catalog of known cetacean behaviors and invite a broader discussion about how river dolphins adapt their social signaling to the ecological particularities of freshwater systems. These insights are not only academically meaningful but also pivotal for informing field-based conservation strategies that acknowledge and protect the social complexity of Amazon river dolphins.
Future research directions: questions to answer and methods to deploy
The discovery of aerial urination in Amazon river dolphins opens a suite of promising research avenues. To move from plausible hypotheses to a more definitive understanding, scientists will benefit from a combination of observational, experimental, and non-invasive analytical approaches that respect animal welfare and ecological integrity. A primary objective for future work is to determine the consistency of the behavior across populations, river systems, and seasonal cycles. Do similar displays occur in other parts of the Amazon or in other freshwater cetacean species, and do frequencies vary with environmental factors like prey availability, water clarity, or river connectivity? Longitudinal cross-population comparisons could illuminate whether this is a species-wide phenomenon or a context-specific adaptation.
Advancements in non-invasive monitoring techniques will be critical. Hydroacoustic sensors, drone-based visual surveys, and high-resolution video analysis can help quantify the spatial and temporal dynamics of aerial urination events with greater precision. Additionally, non-invasive chemical sampling—where feasible—could explore whether the emitted urine contains compounds of interest that other dolphins might detect and respond to. Such analyses would require careful methodological design to avoid disturbing the dolphins, ensure accurate sample collection, and interpret any chemical signatures in light of the river’s unique chemical milieu.
Investigating social outcomes associated with aerial urination will also be valuable. Researchers could examine whether the presence of a receiver under the spray correlates with subsequent social behaviors, such as cooperative foraging, alliance formation, or changes in mate competition. This line of inquiry would help determine whether the display has a direct impact on social success or status within a population. Controlled observational studies, combined with social network analyses, could uncover patterns in how individuals respond to this signal over time and whether recognition of signalers contributes to stable social ties or shifting hierarchies.
A comparative framework could further enrich understanding. By analyzing similar displays or chemical signaling mechanisms across cetacean species with diverse social structures, researchers can identify shared principles and species-specific adaptations. Such cross-species comparisons would contribute to broader theories of how marine mammals negotiate social complexity in habitats with varying acoustic, visual, and chemical landscapes. Integrating ecological modeling with field data could illuminate how environmental variability shapes the evolution and deployment of signaling modalities in riverine cetaceans.
Finally, the study invites a respectful and collaborative dialogue with local communities and indigenous knowledge systems. Many cultures living along the Tocantins and other rivers have long observed dolphins and their behaviors, sometimes weaving these creatures into local lore and ecological knowledge. Engaging with communities can enrich scientific interpretation, provide context for behavior patterns, and foster stewardship for river ecosystems. Ethical, inclusive science that values local perspectives can strengthen research outcomes and promote conservation that aligns with the needs and wisdom of communities who share these waterways with Amazon river dolphins.
Synthesis: what this behavior adds to our picture of dolphin communication
The documented aerial urination by Amazon river dolphins represents a rare and intriguing addition to the spectrum of known cetacean signaling behaviors. While the exact function remains to be established, the pattern of social context, the prevalence of receivers under the spray, and the duration dynamics all point toward a communicative role with social significance. The observations challenge assumptions about how cetaceans use signaling in freshwater environments, where visibility, hydrodynamics, and ecological pressures differ from open oceans. By situating this behavior within broader frameworks of chemical signaling, multi-modal perception, and social dynamics, researchers can build a more comprehensive understanding of how Amazon river dolphins coordinate within complex social networks.
The tale underscores how scientific discovery often unfolds at the intersection of culture, curiosity, and careful observation. Folklore about shapeshifting has inspired questions about how dolphins communicate and interact with other dolphins and their environment. The four-year field study demonstrates that long-term, patient observation can reveal patterns that single-visit studies might miss, and it highlights the value of documenting social life in natural habitats where ecological variability shapes behavior. As the research community weighs hypotheses about chemical signaling, acoustic contributions, and social interpretation, the Amazon river dolphin case stands as a reminder that even in well-studied groups, there are still surprising behaviors waiting to be understood.
The findings encourage a broader, more nuanced view of cetacean communication research, particularly for freshwater species facing unique ecological constraints. They invite researchers to explore the interface between social signaling, sensory ecology, memory, and social learning in dolphins. Ultimately, this line of inquiry contributes to a richer picture of how nonhuman animals construct meaning through behavior, how signals circulate within social networks, and how environmental context influences the evolution of communication systems. By continuing to document, analyze, and interpret such displays, scientists can illuminate the social fabric of Amazon river dolphins and deepen our appreciation for the diversity of signaling strategies across the animal kingdom.
Conclusion
In four years of fieldwork on the Tocantins River, Amazon river dolphins revealed an unexpected social signal: aerial urination enacted by males, sometimes in the presence of several potential receivers. The documented 36 cases, drawn from nearly 219 hours of observed activity, show a pattern in which the initiator often displays while nearby conspecifics watch, making the act a clear social event rather than a solitary physiologic release. While researchers propose several plausible mechanisms—including chemical communication, acoustic signaling, and social display—they emphasize that the function is not yet proven and that more research is needed to disentangle the relative contributions of each channel and the broader social outcomes.
This phenomenon sits at the intersection of folklore, field biology, and sensory ecology, illustrating how a single, striking behavior can open a window into the intricate social lives of a species that thrives in a challenging, dynamic river system. The observation invites continued, careful study across populations and environments, with future work likely leveraging non-invasive methods to probe chemical cues, acoustic environments, and social networks. By pursuing these questions, scientists can deepen their understanding of Amazon river dolphins, their adaptive communication strategies, and the ways in which environmental context shapes the evolution of social signals in aquatic mammals. The study thus adds a meaningful thread to the tapestry of cetacean behavior, offering new directions for inquiry and renewed appreciation for the complexity of life beneath river surfaces.
