Mistaken identity? Visual similarities of marine debris to natural prey items of sea turtles

Qamar A Schuyler,Chris Wilcox,Kathy Townsend,N Marshall,B Hardesty

doi:10.1186/1472-6785-14-14

Qamar A Schuyler, Chris Wilcox + Show 3 more

Open Access

https://doi.org/10.1186/1472-6785-14-14

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Abstract

BackgroundThere are two predominant hypotheses as to why animals ingest plastic: 1) they are opportunistic feeders, eating plastic when they encounter it, and 2) they eat plastic because it resembles prey items. To assess which hypothesis is most likely, we created a model sea turtle visual system and used it to analyse debris samples from beach surveys and from necropsied turtles. We investigated colour, contrast, and luminance of the debris items as they would appear to the turtle. We also incorporated measures of texture and translucency to determine which of the two hypotheses is more plausible as a driver of selectivity in green sea turtles.ResultsTurtles preferred more flexible and translucent items to what was available in the environment, lending support to the hypothesis that they prefer debris that resembles prey, particularly jellyfish. They also ate fewer blue items, suggesting that such items may be less conspicuous against the background of open water where they forage.ConclusionsUsing visual modelling we determined the characteristics that drive ingestion of marine debris by sea turtles, from the point of view of the turtles themselves. This technique can be utilized to determine debris preferences of other visual predators, and help to more effectively focus management or remediation actions.

Highlights

There are two predominant hypotheses as to why animals ingest plastic: 1) they are opportunistic feeders, eating plastic when they encounter it, and 2) they eat plastic because it resembles prey items
The predominant hypotheses are that 1) turtles, as opportunistic feeders, consume items in proportion to what they encounter in the environment, including plastics; and 2) that turtles feed on plastic because of its similarity to prey; jellyfish [4,5]
The mixed effects modelling results indicate that sea turtles select the debris they ingest based on a variety of physical properties

Summary

Introduction

There are two predominant hypotheses as to why animals ingest plastic: 1) they are opportunistic feeders, eating plastic when they encounter it, and 2) they eat plastic because it resembles prey items. To assess which hypothesis is most likely, we created a model sea turtle visual system and used it to analyse debris samples from beach surveys and from necropsied turtles. Like many other marine taxa, are increasingly prone to marine debris ingestion and associated problems [1]. The predominant hypotheses are that 1) turtles, as opportunistic feeders, consume items in proportion to what they encounter in the environment, including plastics; and 2) that turtles feed on plastic because of its similarity to prey; jellyfish [4,5]. When presented with both chemical and visual cues, leatherback

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