In the intricate landscapes of South Africa’s Cape Peninsula, a troop of wild chacma baboons embarks on daily journeys marked by a surprisingly orderly pattern. Contrary to longstanding assumptions in animal behavior research, these primates do not form travel lines driven by tactical positioning for protection or resource acquisition. Instead, their linear formations emerge as vivid reflections of their underlying social fabric. Researchers at Swansea University, employing high-resolution GPS tracking over extensive observations, have unveiled that baboons walk in progressions not as a conscious survival strategy, but to stay close to their closest friends within the troop.
Historically, the phenomenon of baboons traveling in structured lines—termed ‘progressions’—has intrigued ethologists. Initial hypotheses posited either randomness in their procession order or, alternatively, intentional placements to defend vulnerable individuals from predator attack. Others suggested hierarchies might dictate formations, with dominant or leading animals coordinating group movements toward food and water resources. Yet, these explanations carried inconsistencies or lacked empirical support from detailed movement and social data.
The latest study, methodically analyzing 78 individual travel progressions over a 36-day period, challenges these earlier theories with compelling evidence. The Swansea team comprehensively tested four specific hypotheses thought to explain progression order: the risk hypothesis centered on protecting vulnerable members, the competition hypothesis emphasizing resource access, the group decision-making hypothesis highlighting leadership dynamics, and finally, the social spandrel hypothesis proposing that social bonding patterns emerge as incidental by-products influencing travel order. The data decisively supported the latter scenario, revealing social relationships as the critical determinant of baboon movement order.
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Central to this discovery is the concept of the “social spandrel.” Borrowed from architectural terminology referring to spaces that arise incidentally between structural elements rather than as focal design features, the biological spandrel refers to traits emerging as side effects rather than direct adaptations. In baboon progressions, the consistent travel order isn’t an evolved survival strategy but a consequence of the troop’s social network—individuals simply travel alongside their nearest social partners, producing the observed structured lines without deliberate intent to optimize safety or resource competition.
Detailed GPS tracking enabled unprecedented precision in mapping individual baboon movements within the group. By overlaying these spatial data with social interaction metrics and dominance hierarchies, researchers identified that high-ranking, socially well-connected individuals tended to occupy the central positions within the travelling line. Conversely, lower-ranking baboons frequently found themselves at the front or rear ends. Unlike traditional leadership or risk avoidance models, those at the front were not necessarily guiding the group but simply occupying locations determined by their associative bonds and social status.
Such insights redefine how collective animal behavior is perceived, emphasizing the importance of social structure as an autonomous driver. The baboons’ movement patterns underscore a complex social calculus where friendship networks dictate spatial arrangement during progression. The findings illustrate that social affiliations can manifest morphological-like behavioral arrangements incidentally, elevating the concept of spandrels in understanding animal societies.
Moreover, these results prompt reconsideration of presumed functional explanations in ethology. The clear dissociation between movement order and immediate survival advantages—like predator avoidance—highlights that some animal behaviors may not be optimized for direct environmental benefits but emerge from intricate social milieus. This nuance enriches evolutionary biology’s conceptual framework by illustrating that collective behaviors can arise devoid of explicit adaptive aims, expanding the vocabulary for interpreting animal group dynamics.
Dr. Andrew King, an Associate Professor at Swansea University, emphasized this paradigm shift: “Our data reveal that baboons do not position themselves based on perceived risk or resource competition during group travel. Instead, social bonds are the architecture of progression order. This challenges longstanding ideas about animal movement and leadership, steering the conversation toward a more sophisticated understanding of social cognition and group dynamics in primates.”
The implications extend beyond baboon communities and may refine interpretative models applied to other social species. By recognizing social spandrels as legitimate outcomes of complex interaction networks, ecologists and behavioral scientists can better parse the emergent properties of animal collectives. This approach invites fresh inquiries into how social affiliation patterns in elephants, dolphins, or primates influence not only travel but other cooperative behaviors.
Lead author Marco Fele, a doctoral student at Swansea University, elaborated on the biological significance: “Strong social bonds in baboons correlate with longevity and reproductive success, but our findings suggest that the order in travel progressions is not directly selected for these outcomes. Instead, it exemplifies a behavioral by-product—an emergent structural pattern shaped by social ties rather than immediate ecological pressures.”
Advancements in GPS tracking technology were instrumental in attaining such detailed movement resolution, marking a significant leap from prior observational studies reliant on visual counting and positioning estimates. This technological enabling allowed researchers to pair spatial data with rich social metadata, fostering integrated analyses unachievable in past decades.
Importantly, the baboon troop’s familiarity with their environment also factors into the interpretation. Since their travel destinations—such as sleeping sites—are well known, traditional leadership and navigational decision-making cues are less relevant during these progressions. The social spandrel concept gains further plausibility under these stable environmental conditions, where group navigation is predictable and not contested.
From a broader perspective, this study contributes to ongoing debates about how collective animal behaviors emerge and stabilize. It highlights how social network structures can inadvertently give rise to persistent behavioral phenotypes—like progression order—disentangled from direct adaptive functions. This recognition advocates for more nuanced theoretical models that accommodate complexity and indirect causality in animal societies.
As scientists continue to decipher the layers underpinning animal group behavior, this research exemplifies a paradigm where social relationships take precedence as architects of collective movement. It simultaneously challenges oversimplified notions of leadership or defensive tactics as sole drivers of spatial order in animal groups, underscoring the social brain’s profound influence on natural history.
This deeper understanding of baboon progressions not only enriches primatology but also bridges ethology with network theory and evolutionary biology. By framing travel order as a social spandrel, researchers open pathways to appreciate how emergent properties shape animal behavior, sometimes independently from immediate survival utility or evolutionary selection pressures.
In sum, the baboons walking in line on South Africa’s Cape Peninsula illustrate a compelling lesson in social-driven behavioral patterns. They reveal that collective behavior can be as much a mosaic of friendships and social bonds as a manifestation of environmental adaptation. This research reorients how we interpret animal group dynamics, emphasizing the delicate interplay between social cognition and emergent behaviors in the wild.
Subject of Research: Animals
Article Title: Baboon travel progressions as a ‘social spandrel’ in collective animal behaviour
News Publication Date: 12-Mar-2025
Web References:
https://academic.oup.com/beheco/advance-article/doi/10.1093/beheco/araf022/8071582?searchresult=1
http://dx.doi.org/10.1093/beheco/araf022
Image Credits: Vittoria Roatti
Keywords: Animal science, Animal migration, Behavioral ecology, Animal communication
Tags: animal behavior researchanimal survival strategiesbaboon movement analysisbaboon progression patternsbaboon troop dynamicsbaboons social behaviorethology of baboonsfriendship in primatesGPS tracking in wildlife studiesprimate social structuressocial fabric of animal groupsSouth Africa wildlife observations
