Marine debris ingestion and Thayer's law – The importance of plastic color

In recent years marine plastic pollution has gained considerable attention as a significant threat to marine animals. Despite the abundant literature related to marine debris ingestion, only a few studies attempted to understand the factors involved in debris ingestion. Plastic ingestion is commonly attributed to visual similarities of plastic fragments to animal's prey items, such as plastic bags and jellyfish. However, this simple explanation is not always coherent with the variety of debris items ingested and with the species' main prey items. We assess differences in the conspicuousness of plastic debris related to their color using Thayer's law to infer the likelihood that visual foragers detect plastic fragments. We hypothesize that marine animals that perceive floating plastic from below should preferentially ingest dark plastic fragments, whereas animals that perceive floating plastic from above should select for paler plastic fragments. •Thayer's law may help to understand the likelihood that animals have to ingest plastic.•Ingestion of plastic debris may be related to plastic conspicuousness due its color.•Animals that perceive plastic from below may be more prone to ingest dark objects.•Animals that perceive plastic from above may be more prone to ingest light objects. Thayer's law may help to understand the likelihood that animals have to ingest plastic, where the plastic color and foraging strategy of the marine animals are key factors.