BRIEF RESEARCH REPORT article

Front. Mar. Sci., 08 June 2026

Sec. Marine Megafauna

Volume 13 - 2026 | https://doi.org/10.3389/fmars.2026.1840078

Documentation of remora (Remora remora) attachment to a nesting olive ridley sea turtle (Lepidochelys olivacea) in Playa Pejeperro, Costa Rica

  • 1. University of West Florida, Department of Biology, Hall Marcus College of Science and Engineering, Pensacola, FL, United States

  • 2. Comunidad Protectora de Tortugas de Osa (COPROT), Puerto Jiménez, Costa Rica

  • 3. University of Miami, Department of Environmental Science and Policy, Miami, FL, United States

Abstract

Despite being known to regularly associate with diverse marine megafauna, the complexity, stability, and drivers underlying remora symbioses remain largely understudied. Recent studies have documented the presence and persistence of remora associations even in the face of physiologically challenging conditions and have indicated that remora-host symbioses may be more selective than previously understood. Here, we contribute to this growing body of knowledge by documenting an observation of a live remora (Remora remora) remaining attached to a nesting olive ridley sea turtle (Lepidochelys olivacea) after the turtle had emerged from the ocean to nest on Pejeperro Beach, Osa Peninsula, Costa Rica. Although remora attachment on nesting turtles has been previously described, this observation adds meaningful insight into the geographic range, frequency, and species involved in these interactions. Continued observation and documentation of cryptic behavior is critical for improving scientific understanding of these relationships and may indicate that associations between remoras and individual hosts may be more obligate than previously understood.

1 Introduction

Remoras are well known for their tendency towards phoresis, attaching themselves to other fish, elasmobranchs, marine mammals, and even sea turtles to expend less energy while traveling and feeding (; ; ; ; ; ; ; ). This symbiotic behavior is extensively debated in modern literature, and it remains unclear whether it is truly mutualistic, commensalistic, or parasitic (; ; ; ; ; ). Despite being an ecological relationship, the development of remora-host symbioses appears to exist on the spectrum between facultative and obligate symbiotic associations rather than exclusively in one category as remoras have evolved a modified dorsal fin adhesive disc to facilitate their attachment to their hosts but can exist independent of their host ().

While remora-host associations are most frequently observed in situ, there have been several documentations of remoras accompanying their hosts out of the water. Most notably, remoras have been documented accompanying nesting leatherback sea turtles (Dermochelys coriacea) in French Guiana and olive ridley sea turtles (Lepidochelys olivacea) in Mexico (, ; ; ). Despite these occurrences, the extent to which these relationships have been documented across nesting beaches remains unexplored. Here we document the occurrence of a remora remaining attached to a nesting olive ridley sea turtle on the Osa Peninsula of Costa Rica.

2 Methods

Comunidad Protectora de Tortugas de Osa (COPROT; https://www.tortugasdeosa.org) research assistants conduct daily nighttime sea turtle nesting surveys on Pejeperro Beach, Costa Rica between June and April. Pejeperro is part of the Rio Oro National Wildlife Refuge, an area that extends 2km from the coast to the ocean. With 7,000 olive ridley and 600 green sea turtle (Chelonia mydas) nests in 2024 alone, Pejeperro is one of the most important nesting sites on the Pacific coast of the country for these species ().

During these routine surveys, research assistants documented nesting frequency, nesting location, turtle behavior, and turtle size for each individual turtle encountered. Turtle size was determined to be the average of three curved carapace length and three curved carapace width measurements captured using a soft tape measure. Any notable secondary observations, including the presence of any hitchhiker species emerging from the ocean with the nesting turtle, were also recorded. Secondary observations were documented using red light and an iPhone 16E (Apple Inc.) on night exposure mode.

3 Results

On September 24th, 2025 at 22:29, COPROT research assistants patrolling Pejeperro beach encountered a nesting female olive ridley sea turtle having just emerged from the ocean. Upon initial encounter, researchers observed a large common remora (Remora remora) attached to the turtle’s second and third left costal scutes (Figure 1). Researchers observed the remora and turtle for 19 minutes before a research assistant removed the remora from the turtle and returned it to the ocean to allow for accurate collection of the turtle’s curved carapace width measurements. During the 19 minutes of observation, the remora remained relatively still except for periodically flexing its opercula (Figure 1a). Once the research assistant approached the remora to remove it, the remora began to shift its body position on the turtle (Figure 1b). When it was fully removed, the remora began to writhe and quickly moved away from the researcher once it was returned to the ocean, indicating that it was still alive despite being removed from the water for an extensive period.

Figure 1

The turtle had an average curved carapace length of 68.4 centimeters and an average curved carapace width of 72.6 centimeters. Using these measurements as known standards, the remora was determined to be approximately 28cm in length during post-observation measurements generated from photographs (Fiji v2.16.0). As the researchers viewed the entire interaction in red light, no accurate color measurements could be made, though the remora appeared to be the same shade as the olive ridley turtle, which are typically grey.

The turtle was seemingly unaffected by the presence of the remora and demonstrated standard nesting behaviors, initiating egg laying at 22:48.

4 Discussion

This observation supports other documentation of remoras remaining attached to nesting turtles and adds meaningful context to the scope and geographical range of these interactions (; ). Previous work has recorded these interactions in both the Pacific Ocean (Mexico; ) and the Atlantic Ocean (French Guiana; ; , ). However, the addition of our observation in Costa Rica shows that this behavior is present in North, Central, and South America suggesting that it may be a common occurrence across multiple populations and species of marine turtles.

Remoras have adapted adhesive discs and hitchhiking behavior to improve their fitness (). The ability to physically attach to a host and to swim with that host for prolonged periods of time decreases their energy usage and provides them with opportunities to feed (). However, it seems energetically costly for a remora to associate with a host leaving the water especially as it can lead to mortality, as has been documented with other nesting turtles (; , ; ). Evidence from studies of remoras associating with other marine megafauna indicate that these relationships may not be temporary and that individual remoras may have a more complex and behavioral attachment to their unique host (; ). Specifically, documented a single remora associating with a parrotfish host for 238 days despite the presence of other potential hosts, including large elasmobranchs, in the area.

If remoras display fidelity to individual hosts, this may explain observations of their continued association with those hosts even in conditions that may lead to their own mortality (, ; ). Pursuing symbiosis even in physiologically taxing circumstances is not a new occurrence. Remoras have been documented travelling into the deep sea with manta and shark hosts to depths that had previously been hypothesized to be too challenging for them to physically survive at independently (). Paired with documentation of remoras persisting with specific, individual hosts, even when other hosts are available to them (; ; E. Yeager, unpublished data), these observations suggest that remoras may be unwilling to risk losing their specific host, even when that continued fidelity subjects them to hypothetically harmful situations in order to maintain their association. However, documentation of remora persistence in these extreme environments for extended periods of time warrants additional exploration of remora physiology and behavior.

5 Conclusion

Observations like the one presented here add to the growing body of literature documenting the nature of remora-host symbioses. Apparent attachment, even in extenuating circumstances that can lead to remora mortality, indicate that remora-host relationships may not be entirely facultative for remoras but rather, at least partially, obligate (; , ; ). This notably contributes to scientific understanding of transient, cryptic relationships between marine megafauna which have historically been considered to be facultative (). Continued observation of turtle nesting behavior will provide additional insight into the global scope of these interactions across marine turtle species and can provide meaningful insight into the complex relationships underlying remora associations in marine environments.

Statements

Data availability statement

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

Author contributions

MB: Conceptualization, Data curation, Investigation, Project administration, Visualization, Writing – original draft, Writing – review & editing. VP: Funding acquisition, Project administration, Resources, Supervision, Writing – review & editing. EY: Conceptualization, Funding acquisition, Supervision, Writing – original draft, Writing – review & editing.

Funding

The author(s) declared that financial support was received for this work and/or its publication. This work was funded in part by the Florida Sea Grant-Guy Harvey Fellowship and the University of Miami Abess Center.

Acknowledgments

We are deeply grateful for the entire COPROT team and all of COPROT’s partners for making this project possible. We would also like to thank Julia Saltzman for helping to initiate this project by connecting co-authors MB. EAY would like to thank the Shark Research and Conservation Program at the University of Miami, the Florida Sea Grant-Guy Harvey Fellowship and the University of Miami Abess Center for their support.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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Publisher’s note

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References

Summary

Keywords

behavior, cryptic relationship, nesting, Pacific Ocean, symbiosis, turtle

Citation

Bullock MJ, Peña Eisele V and Yeager EA (2026) Documentation of remora (Remora remora) attachment to a nesting olive ridley sea turtle (Lepidochelys olivacea) in Playa Pejeperro, Costa Rica. Front. Mar. Sci. 13:1840078. doi: 10.3389/fmars.2026.1840078

Received

26 March 2026

Revised

07 May 2026

Accepted

18 May 2026

Published

08 June 2026

Volume

13 - 2026

Edited by

Xuelei Zhang, Ministry of Natural Resources, China

Reviewed by

Hector Barrios-Garrido, University of Zulia, Venezuela

Nupur Kale, Swansea University, United Kingdom

Updates

Copyright

© 2026 Bullock, Peña Eisele and Yeager.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Emily A. Yeager,

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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