DOI: 10.5061/dryad.ns1rn8q5t
title: Impact of marine hitchhiker load on host energy intake

description: Determining the energetic and fitness trade-offs associated with symbiotic
 relationships (mutualism, commensalism, or parasitism) can reveal the
 implications of symbiosis for species and ecosystem health. To identify
 hitchhiker impact on sea turtles, this study reviewed global literature
 and examined the association between remoras (Echeneis naucrates) and
 green turtles (Chelonia mydas) at a high-density foraging site in the Red
 Sea using SCUBA and video (n = 71 observations) in October 2023. Previous
 evidence of remora-sea turtle association is limited to qualitative
 observations from the Atlantic and Pacific Oceans. The results show that
 depth significantly impacted the number of remoras per turtle (p &lt;
 0.05). Turtle grazing rate was affected by remora load (p &lt; 0.05),
 decreasing by ~30% across the load range from a mean of 22.8 bites min-1
 (0 remoras) to 15.6 bites min-1 (3 remoras). There was little evidence of
 benefit to turtles, with only one observation of a remora cleaning a
 turtle's carapace. The observed reduction in grazing effort suggests
 potential impacts on green turtle body condition over time, which may
 affect growth, reproduction, and population health, warranting long-term
 investigation. These findings present the first quantitative evidence that
 the remora-sea turtle relationship shifts from commensalism to parasitism
 as remora load increases, demonstrating the potential costs of hitchhikers
 for sea turtles.
description: # Impact of marine hitchhiker load on host energy intake Dataset DOI:
 [10.5061/dryad.ns1rn8q5t](https://doi.org/10.5061/dryad.ns1rn8q5t) ##
 Description of the data and file structure This repository contains data
 used in Kale et al. (2025) to examine the costs and benefits associated
 with remoras (*Echeneis naucrates*) hitchhiking on green turtles
 (*Chelonia mydas*) in the Egyptian Red Sea. The file includes data
 collected during SCUBA surveys. **Study overview** To improve our
 understanding of the remora-sea turtle relationship, we explored the
 following relationships: 1\)    Remora presence/absence *vs* turtle size
 2\)   Mean number of remoras per turtle (hereafter remora load) *vs* depth
 3\)   Mean grazing rate per turtle *vs* turtle size, mean remora load per
 individual, and depth ### Files and variables #### File:
 Data_Marine_hitchhiker_impact.csv **Description:** This file contains data
 collected during SCUBA surveys to examine the remora-green turtle
 relationship using logistic and multiple-stepwise linear regressions.
 Number of variables: 15 Number of header rows: 1 Number of rows: 71 #####
 Variables * site: (character) name of site where data were collected *
 date: (numeric) date when data were collected * start_time: (numeric) time
 when the dive survey started * session: (character) time of day
 (morning/afternoon) * interval.h: (numeric) time elapsed between repeated
 observations in hours (&lt;1, &lt;12, &gt;12, &gt;24, NA) *
 id: (character) turtle ID * depth.m: (numeric) position of turtle
 underwater (in meters) * scl.cm: (numeric) visually estimated straight
 carapace length SCL~max~ of the turtle (in centimeters) * diff: (numeric)
 change in estimated SCL~max~ of turtles between repeated observations (in
 centimeters) * stage: (character) life stage of observed turtle
 (immature/mature) * tail: (character) sex based on presence/absence or
 length of tail (juvenile/male/female) * p.a: (numeric) presence/absence of
 remora (1/0) * remora: (numeric) number of remoras per turtle *
 rem.diff: (numeric) change in remoras per turtle between repeated
 observations * grazing.rate: (numeric) bites per minute for each turtle
 **Note:** NAs indicate where data were not applicable. Data type:
 character, numeric ## Code/software All analyses were performed in R
 v4.2.3 (R Core Team 2024).