Abstract
Titan triggerfish (Balistoides viridescens) are among the most territorial reef fishes, known for aggressively defending nests from intruders. In the Maldives’ Fuvahmulah atoll, where tiger sharks (Galeocerdo cuvier) aggregate in high numbers year-round, we opportunistically documented 10 interactions between these species from February to August 2024 during daily diving operations. Video footage from experienced divers was analyzed to identify and categorize aggressive behaviors, defined as bites (rapid, forceful closure of the jaws on the shark’s body) and chases (short pursuits following an aggressive display). All observed aggression was initiated by titan triggerfish, most often targeting the caudal fin of individual tiger sharks. Biting accounted for 70% of interactions, with chases comprising the remainder; over half of bites were immediately followed by a chase. Several interactions occurred near the new moon, coinciding with the species’ nesting period, suggesting that many of these interactions may have been linked to breeding-season territoriality; however, the opportunistic nature of the observations precluded any formal analysis of lunar phase patterns. These behaviors likely function as risk-based defense, exploiting anatomical vulnerabilities to deter much larger predators. The high frequency of these interactions in a location with artificially dense tiger shark populations suggests that provisioning and predator aggregation may increase the likelihood of such cross-trophic encounters. By linking detailed behavioral observations with the ecological context of predator aggregation, this study highlights the defensive capabilities of titan triggerfish and raises questions about how ecotourism-driven changes in predator distribution influence the behavior of non-target reef species.
Data availability
Data and data sets are available from the corresponding author upon reasonable request.
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Acknowledgements
We want to extend our sincere gratitude to the individuals who contributed to this study by providing valuable video footage of interactions between titan triggerfish and tiger sharks. This study could not have been completed without the support of Fuvahmulah Dive School and Pelagic Divers Fuvahmulah, and the authors are grateful for their assistance. The authors extend special thanks to Mathieu Noé, Anoos, Sadhar Suresh, Nikita Kornilov, and Ahmed Ashhal Abdulla for capturing and sharing the essential videos that formed the foundation of this research. Their efforts were crucial in documenting the behavioral dynamics observed in this study. We also thank Luca Asshauer and Max Kimble for their assistance with the artistic figures included in this manuscript. Additionally, we thank Gonzalo Araujo for their insightful feedback during the analysis process. This research would not have been possible without the support and contributions of all those involved. The study was conducted following the guidelines and under the research permits issued by the Ministry of Fisheries, Marine Resources and Agriculture, Maldives (annually renewable permit: 30-D/PRIV/2021/190). The methods were non-invasive, ensuring no harm was caused to the animals involved.
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This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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Nathan Perisic and Filippo Bocchi were responsible for the analysis, manuscript writing, and review. Ahmed Inah and Tatiana Ivanova contributed to the study’s inception, preparation of the manuscript, and review.
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Bocchi, F., Perisic, N., Inah, A. et al. Defensive responses of titan triggerfish to tiger sharks at a provisioned reef.
Sci Rep (2025). https://doi.org/10.1038/s41598-025-31560-7
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DOI: https://doi.org/10.1038/s41598-025-31560-7
Keywords
- Species interaction
- Indian ocean
- Sharks
- Tropical ecology
- Triggerfish
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Source: Ecology - nature.com
