The study, led by Celeste L. Schonberg of the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science, together with Holli C. Eskelinen of Dolphins Plus, Kelley A. Winship of the National Marine Mammal Foundation, and Mark J. Xitco Jr. of the Navy’s Marine Mammal Program, exploited a piece of technology few laboratories possess. The Enclosure Video Enrichment, or EVE, system is a computerized cognitive testing platform installed at the Navy facility in San Diego. It allows marine mammals voluntarily participating in husbandry and research sessions to interact with on-screen tasks, generating standardized, automated data of the kind that has transformed primate cognition research but has remained scarce for marine mammals.

The task itself was a maze. Each trial presented the sea lion with a layout of barriers on the screen, and success required maneuvering a cursor-like element from a start position to a target while avoiding obstacles. Critically, the researchers designed the layouts so that successful performance demanded short-term forward planning: an animal that simply lunged at the target or followed the most immediate path would run into a trap. Avoiding those traps required the animal to anticipate the consequences of its movements at least a step or two ahead, the cognitive equivalent of checking a route before committing to it.

Seven adult male sea lions completed the full protocol. The experiment consisted of 200 testing trials built from 100 unique maze layouts, which were separated into four trial blocks and repeated randomly across eight testing sessions. This design allowed the team to distinguish between performance on novel layouts and performance on layouts the animals had already seen, a distinction that matters enormously when testing for planning. If an animal is genuinely planning, it should perform well on brand-new configurations; if it is memorizing, its advantage should appear only on repeated exposures.

The researchers scored not just success and failure but the pattern of responses, categorizing trials by layout type, including direct layouts, reversal layouts, away layouts, and layouts requiring an approach-and-return strategy. Response types included clean successes, failures in which the animal fell into a trap, and failures without a trap. This fine-grained scoring was intended to reveal cognitive flexibility, problem-solving strategies, and any evidence that animals adjusted their approach as difficulty increased. A supplementary video released with the paper shows the full range of responses, from a sea lion sailing through a direct layout to one blundering into a trap on a reversal layout.

The results were moderate rather than spectacular. Sea lions achieved moderate success rates across the task, showing that they could use the EVE system and complete maze trials at levels well above pure chance on many layouts. But the more telling result was what did not appear: improvement. Across repeated exposures to the same layouts, success rates did not climb, and response patterns did not shift in ways that would indicate the animals were learning from experience or refining their strategies. In a task where learning should be easy to detect, the absence of a learning curve is itself a finding.

That absence led the authors to conclude that there was limited evidence of planning behavior in this paradigm. If the sea lions were employing short-term forward planning, one would expect them to avoid traps more effectively over time and to perform better on novel layouts as they gained general familiarity with the task structure. Instead, performance stayed flat. The researchers interpret this as suggesting that the sea lions may have relied on strategies other than planning, such as responding to immediate perceptual cues, or that the task’s demands did not align with the species’ natural cognitive strengths.

This is where the study’s comparative framing becomes important. Planning behavior, the ability to act now in anticipation of future states, has been documented in primates, corvids, and a handful of other species, typically using paradigms adapted to each animal’s ecology. Computerized maze tasks have been a staple of primate cognition research precisely because they can be standardized, repeated, and automated. Extending that paradigm to marine mammals is technically ambitious, and the authors emphasize that their goal was as much methodological as cognitive: to expand computerized testing beyond primates and to generate data that can be compared across species. The sea lion result, on its face a negative finding, still delivers value by marking the boundary of where this paradigm succeeds.

The authors are careful about interpretation. A flat learning curve in a computerized maze does not prove that sea lions cannot plan; it shows that this particular task, in this particular context, did not elicit measurable planning or learning. Species-specific cognition is shaped by adaptations and environmental conditions, and a pinniped that navigates three-dimensional underwater environments, hunts cooperatively, and relies on vibrissae and hearing rather than vision may simply not engage with a two-dimensional visual maze the way a primate does. The sensory and ecological mismatch between the test and the test-taker is a central theme of the paper, which argues that comparative cognition research must account for how adaptations influence performance on human-designed tasks.

There is also a welfare and husbandry dimension. The EVE system was developed as video enrichment, and voluntary participation in cognitive testing is a form of enrichment in itself for animals in managed care. The fact that seven sea lions completed 200 trials across eight sessions demonstrates that the platform works, that the animals engage with it, and that it can be deployed repeatedly without coercion. For the Navy Marine Mammal Program, whose animals participate in research and operational tasks, tools that measure cognition while providing enrichment serve dual purposes. For the broader research community, the study establishes a working pipeline for computerized marine mammal testing that future studies can refine, perhaps with designs that better match pinniped sensory worlds.

For now, the headline result is a study in cognitive humility. Sea lions, animals celebrated for trainability and social intelligence in managed care, confronted a maze task engineered to reward forward planning and did not show the improvement or response patterns that planning would produce. Whether that reflects a genuine absence of planning capacity, a mismatch between the paradigm and the species, or motivational and contextual factors unique to this setting remains an open question, and one the authors frame explicitly as a matter of species-specific cognition shaped by evolutionary history. What the study does establish is that the question can now be asked with standardized, automated tools, and that the answers, positive or negative, will accumulate in a form that can be compared across species, laboratories, and lines of evolutionary descent.

Subject of Research: Investigating planning behavior in California sea lions (Zalophus californianus) using computerized MAZE testing

Article Title: Investigating planning behavior in California sea lions (Zalophus californianus) using computerized MAZE testing

Article References: Schonberg, C. L., Eskelinen, H. C., Winship, K. A., & Xitco, M. J., Jr. (2026). Investigating planning behavior in California sea lions (Zalophus californianus) using computerized MAZE testing. Animal Cognition. https://doi.org/10.1007/s10071-026-02115-8

Image Credits: AI Generated

DOI: 10.1007/s10071-026-02115-8

Keywords: Investigating, planning, behavior, California, lions, Zalophus, californianus, computerized, MAZE, testing, scientific research

The study, authored by Rosa María Carreño Sánchez, a researcher at the Lucio Anneo Séneca Institute of Classical Studies at UC3M, was published in the Revista General de Derecho Romano. Rather than relying on literary sources or artistic depictions, which typically capture only the dramatic climax inside the arena, Carreño Sánchez turned to the legal record itself. Her analysis centers on two imperial constitutions from the Late Empire preserved in the Theodosian Code, the great compilation of Roman law issued under Emperor Theodosius II in the fifth century, and later carried forward into the Justinian Code. These legal texts, she argues, open a window onto everything that happened behind the scenes: the management of resources, the territorial conflicts between communities, and the enormous logistical effort required to keep one of antiquity’s most beloved entertainments running.

Among the most striking findings is evidence of what the researcher describes as a possible state monopoly on lions in late antiquity. As the population of big cats dwindled across the Empire’s territories, imperial authorities moved to guarantee supply for the emperor’s own spectacles and to shut out private competitors. In practical terms, this meant that all lions belonged to the emperor. The implication is remarkable: an animal that had once been hunted freely across North Africa and the Near East became, by law, an imperial asset, its capture and movement regulated with the same seriousness as taxation or military provisioning. The monopoly reflects both the growing scarcity of the animals and the political value the court placed on displaying them, since a spectacular hunt in the arena was a direct statement of the emperor’s power over nature itself.

Enforcing such a monopoly required manpower, and here the study highlights the surprising role of the Roman army. The military did not merely defend frontiers; it also fielded highly specialized units dedicated to the tracking, capture, and guarding of wild beasts along the Empire’s borders. Soldiers designated ad leones, literally assigned to lions, worked alongside specialists known as ursuarii, who handled bears, and vestigiatores, trackers whose job was to follow the spoor of exotic animals through difficult terrain. These designations, preserved in the legal and administrative record, reveal a professionalized hunting service embedded within the military structure, one that turned the Empire’s borderlands into a supply zone for the arenas of Rome and other great cities.

Capturing the animals, however, was only the first stage of a journey that could stretch across thousands of kilometers. Transporting lions, bears, leopards, and other creatures to the capital or to imperial menageries created significant logistical and economic challenges, and it is here that the two imperial constitutions examined in the study become especially revealing. The provinces were required to supply the transport personnel, and the costs were to be borne by local coffers. This arrangement placed a heavy burden on municipal budgets and, predictably, invited abuse. The legal texts document fraudulent practices in which communities or officials imposed undue delays on the transport convoys. Such delays were not merely bureaucratic friction; they could ruin the cities financially, and worse, they could conceal the fraudulent diversion of the animals to unauthorized private spectacles, effectively stealing imperial property for someone else’s show.

The imperial response was characteristically severe. To curb these abuses, the administration imposed heavy fines, payable in gold, on military commanders who failed to comply with the regulations governing animal transport. The penalty structure is significant for what it tells us about how the Empire viewed the trade in exotic beasts: the officers responsible for moving the animals were held personally and financially accountable, and the currency of punishment was the same precious metal that underpinned the late imperial fiscal system. In other words, the movement of a lion from a frontier province to an amphitheater was treated as a matter of state, policed by law, financed by provinces, and enforced against soldiers with monetary sanctions.

Understanding why the Empire invested so much in this system requires appreciating the cultural weight of the venationes. Unlike gladiatorial combat, which gradually died out under the combined pressure of Christian moral condemnation and the enormous cost of organizing fights, the animal hunts proved remarkably durable, surviving for centuries after other forms of arena entertainment had faded. The study frames their longevity in terms of what they symbolized: displays of human dominion over nature and of the grandeur of imperial power. Every beast paraded and dispatched in the sand was a living trophy of the Empire’s reach, evidence that its armies and administrators could extract wonders from the farthest provinces and deliver them to the crowd. That symbolism kept the venationes at the heart of public entertainment long after the gladiator had become a memory.

The phenomenon was not confined to the capital. The study emphasizes that this massive spectacle industry spread throughout the Roman Empire, including Hispania, the Iberian Peninsula that remains one of the richest archaeological landscapes for Roman arena culture. A prime example is the colossal amphitheater at Italica, near modern Santiponce in the province of Seville, one of the largest such structures in the entire Empire. Its sheer scale is astonishing given its setting: the building was capable of hosting the full range of gladiatorial spectacles, including venationes, in a city of barely 8,000 inhabitants. That a modest urban community could support an arena of such magnitude underscores how deeply the appetite for animal spectacles penetrated provincial society, and how far the supply network of captured beasts had to extend to satisfy it.

Methodologically, the research is a literature review grounded in legal history, and its central claim is about what the law can reveal where other sources fall silent. Literary accounts and cinematic reconstructions show audiences only the final outcome in the arena, Carreño Sánchez notes, whereas an analysis of Roman law makes it possible to understand what went on behind the scenes: the management of resources, the territorial conflicts, and the enormous logistical effort required by one of the most popular spectacles of antiquity. The two constitutions of the Theodosian Code at the heart of the study, examined in her article De venatione ferarum, function as snapshots of an entire industry, capturing in legal language the soldiers, trackers, provincial treasurers, transport convoys, and commanders whose coordinated work made the games possible.

The broader significance of the work lies in reframing Roman entertainment as an administrative and ecological enterprise. The decline of big cat populations in late antiquity, the imperial monopoly established in response, the militarization of wildlife capture, and the fiscal strains of long-distance animal transport together sketch a picture of an empire managing a natural resource to exhaustion. The venationes, in this reading, were not simply cruelty staged as spectacle; they were the visible tip of a system that connected frontier ecology, military logistics, provincial finance, and imperial ideology. By reading the legal codes closely, the UC3M study recovers the voices of the clerks, commanders, and communities who paid for the lions, moved them, and answered for them in gold, offering historians a far richer account of how Rome put wild beasts in the sand than any arena fresco or Hollywood epic ever could.

Subject of Research: Legal and logistical regulation of wild animal capture and transport for public spectacles in the Roman Empire

Article Title: A UC3M study reveals the military apparatus and laws that made it possible for wild beasts to be brought into the amphitheaters

Article References: A UC3M study reveals the military apparatus and laws that made it possible for wild beasts to be brought into the amphitheaters. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Roman Empire, venationes, Roman law, Theodosian Code, amphitheaters, lions, Roman army, imperial monopoly, animal transport, Hispania, Italica, late antiquity