To Eat or Not to Eat? Debris Selectivity by Marine Turtles

Abstract

Marine debris is a growing problem for wildlife, and has been documented to affect more than 267 species worldwide. We investigated the prevalence of marine debris ingestion in 115 sea turtles stranded in Queensland between 2006–2011, and assessed how the ingestion rates differ between species (Eretmochelys imbricata vs. Chelonia mydas) and by turtle size class (smaller oceanic feeders vs. larger benthic feeders). Concurrently, we conducted 25 beach surveys to estimate the composition of the debris present in the marine environment. Based on this proxy measurement of debris availability, we modeled turtles’ debris preferences (color and type) using a resource selection function, a method traditionally used for habitat and food selection. We found no significant difference in the overall probability of ingesting debris between the two species studied, both of which have similar life histories. Curved carapace length, however, was inversely correlated with the probability of ingesting debris; 54.5% of pelagic sized turtles had ingested debris, whereas only 25% of benthic feeding turtles were found with debris in their gastrointestinal system. Benthic and pelagic sized turtles also exhibited different selectivity ratios for debris ingestion. Benthic phase turtles had a strong selectivity for soft, clear plastic, lending support to the hypothesis that sea turtles ingest debris because it resembles natural prey items such as jellyfish. Pelagic turtles were much less selective in their feeding, though they showed a trend towards selectivity for rubber items such as balloons. Most ingested items were plastic and were positively buoyant. This study highlights the need to address increasing amounts of plastic in the marine environment, and provides evidence for the disproportionate ingestion of balloons by marine turtles.

Plastic ingestion by sea turtles in Paraíba State, Northeast Brazil

“…We did not find a correlation between CCL and the number or mass of ingested plastic items, which is consistent with other studies (Bugoni et al, 2001;Tourinho et al, 2010;Lazar & Gračan, 2011). Although some studies have suggested that juveniles are more prone to plastic ingestion (Balazs, 1985;Bjorndal, 1997;Schuyler et al, 2012); however, we can not presume the same, since in this study only one adult animal was observed.…”

“…Probably, the predominant number of Green Turtles in the present study was due to the fact this species use the coral reefs of the Paraíba coast as a feeding ground (Mascarenhas et al, 2005), favoring their stranding in the study area. Green turtles may be especially prone to plastic ingestion, since this type of debris is commonly found adhered to their main food resource, algae (Reis et al, 2010), but Schuyler et al, (2012) not found significant difference in the plastic ingestion between Green and Hawksbill species. Both species, exhibit similar feeding behavior, with smaller turtles feeding pelagically, and larger turtles shifting to benthic feeding (Bjorndal, 1997).…”

“…Once in the environment, plastics can impact wildlife in a number of ways, including entanglement and ingestion (Tourinho et al, 2010). Plastic ingestion by seabirds, turtles, marine mammals, fishes, and invertebrates has been widely reported over the last decades (Laist, 1997;Stamper et al, 2006;Graham & Thompson, 2009;Schuyler et al, 2012). Sea turtles are prone to this ingestion, which may occur when plastic items are mistaken for natural food such as jellyfish, or when items are accidentally ingested with food (Laist, 1987;Schuyler et al, 2014).…”

Plastic Pollution Patterns in Offshore, Nearshore and Estuarine Waters: A Case Study from Perth, Western Australia

“…These characteristics have identified significant temporal change in plastic assemblages, where concentrations alone yielded no conclusive results (Shaw and Day, 1994;Vlietstra and Parga, 2002). This type-and color-dependent variability has been ascribed to predator selectivity when plastics are mistaken for food (Shaw and Day, 1994;Schuyler et al, 2012), but may also be due to type-dependent density changes and chemical degradation causing discoloration and bleaching (Pérez et al, 2010). Studies that report plastic type and colors, found the dominant proportion of SMPs in the open ocean to be white or clear in color, and composed of hard plastic fragments (Shaw and Day, 1994;Morét-Ferguson et al, 2010;Reisser et al, 2013).…”

Estudo da distribuição de metais em plásticos no litoral de São Paulo: avaliação da poluição por meio de análise de pellets

“…Minchin, 1996Gregory, 2009;Majer et al, 2012;Farrapeira, 2011), enredamento de animais (Laist, 1997;Gregory, 2009), adsorção de poluentes químicos e possível transferência aos organismos (Takada, 2006;Derraik, 2002;Mato et al, 2001;Teuten, 2009;Endo et al, 2005;Rios et al, 2007;Karapanagioti, 2008;Ogata et al, 2009;Frias et al, 2010;Bond et al, 2011;Van et al,2012;Ashton et al, 2010;Holmes et al, 2012) e, também, podem ser ingeridos (Thompson, 2004;Boerger et al, 2010;Davison et al, 2011;Tourinho et al, 2010;Gregory, 2009;Graham & Thompson, 2009;Colabuono et al, 2009;Barbieri, 2009;Yamashita et al, 2011;Simmonds, 2012;Schuyler et al, 2012;Miranda, 2011 (Hall, 2000;Hammer et al, 2012), tornando-se cada vez mais escuros.…”