Sharks and Toys: Playful Behavior or Curious Exploration?

Researchers placed plastic toys into a public aquarium tank housing 13 animals from four shark species and a skate and recorded how the animals interacted with the objects over 12 weeks. The footage shows animals nudging, biting, flicking and even passing through rings — behaviors that resemble play in other species, but the authors stopped short of calling them definitive play.

Study setup. At the Cabrillo Marine Aquarium, the team introduced plastic squid models, rings and heavy sinking tubes into a single mixed-species tank (horn sharks, swell sharks, leopard sharks, and a California skate). The objects were added one hour before feeding, removed at feeding time, and returned 30 minutes after feeding. This routine was repeated once a week for 12 weeks in 2022 while the animals’ interactions were filmed.

What the researchers observed. Early sessions produced limited interaction, but engagement increased over time. Individual differences emerged: some animals repeatedly engaged with toys, others ignored them. Some animals appeared possessive of particular items, and leopard sharks interacted most often. Notably, interactions were more frequent after feeding, suggesting motivations beyond immediate hunger.

“If you ask me casually, that's what we thought they were doing,” says Patrick Sun, a co-author. “We thought they were playing, and I think if we designed a more rigorous study we would prove that they're playing.”

Why the authors avoided the word “play.” The paper’s authors and peer reviewers noted that labeling behavior as play requires stronger evidence: researchers should contrast toy-directed actions with baseline behavior, show that the actions activate reward circuits in the brain, and confirm the behaviors occur in relaxed, unstressed contexts. Because the study did not rigorously address those criteria, the team refrained from using the term "play" in the manuscript.

Expert perspective and interpretation. Outside scientists welcomed the footage but urged caution. Some experts suggested the behaviors could reflect exploration of novel objects rather than play, especially since interest sometimes waned over time. Others emphasized how little is known about shark social behavior, cognition and motivation, and recommended longer or more controlled experiments to untangle curiosity, learning, social dynamics and potential reward-driven activity.

Implications and next steps. The observations open new avenues for research into shark cognition and social behavior. Follow-up studies could include controlled comparisons with baseline behavior, experiments that test whether object interaction is rewarding, physiological measures of stress and reward, and trials across more individuals and settings. For now, the evidence is intriguing but inconclusive: sharks clearly interact with objects in complex ways, but whether that qualifies as play remains an open question.