Behavior Plastic Pollution

The Plastic Playtime Tragedy: How whales and dolphins fall victim to plastic pollution

Rodríguez Y.; Silva, M.A.; Pham, C.P. & Duncan, E.M. Cetaceans playing with single-use plastics (SUPs): A widespread interaction with likely severe impacts. Marine Pollution Bulletin 194 (2023) 115428

Animal Play

Playful behaviour, defined as a “repeated, seemingly non-functional behaviour initiated when the animal is in a relaxing, unstimulating, or low-stress setting” is very common in animals. Further, play involves “interaction with natural elements” without a final intended outcome. It may be easily recognised when it happens, but still is poorly reported and lacks a wide-ranging research approach.

Object play has been detected in many wild animals including primates and elephants. Studying play in terrestrial animals is logistically easier to accomplish than with marine animals. Nevertheless, whales and dolphins have been seen to playfully engage with both living organisms (sponges and seagrass) and artificial objects (marine litter).

Play is linked to the animal’s well-being and is important into advancing physical and cognitive functions. Playing can be either a social or solitary activity, accompanied by movement and object manipulation.

Marine animals’ playful encounters with plastic

Plastic pollution is a human-induced pressure that is responsible for decreasing global biodiversity. Many marine animals ingest plastic items, confusing it with prey, or use it to create shelter, or refuge. It is hypothesised that playful behaviour ultimately leads to the ingestion and entanglement with plastics.

This study investigates the interactions of cetaceans, the order of aquatic mammals including whales, dolphins, and porpoises with plastic litter to better comprehend the underlying factors that contribute to entanglement and ingestion in their natural habitat. To achieve this goal Yasmina Rodriguez and her team carried out an extensive review of scientific literature from Google Scholar and Web of Science, supplemented by a thorough examination of social media platforms (Facebook and Instagram) to identify documented instances of cetaceans interacting with plastic waste worldwide. In addition, the whale-watching operator “Futurismo” on Sao Miguel Island in the Azores Archipelago allocated photographs of “cetacean play” dating back to 2011.

Social media search words included “marine plastics” linked to “cetaceans”, “dolphins”, and “sperm whales”, together with “play” and “interaction”. These words were also translated into two other languages, Spanish and Portuguese for better coverage.

Collected data included species, region, type of ocean, and plastics typology. Further, the colour was noted, as well as the body part touching the plastic item. Cetaceans either touched plastics with their head, dorsal fin, pectoral fins, or fluke.

Behaviours were classified as “animal play” by analysing sequences of pictures, accurate descriptions of the event, and videos to verify playful behaviour.

11 species of whales and dolphins, including the common bottlenose dolphin (Tursiops truncates), spinner dolphin (Stenella longirostris), short-beaked common dolphin (Delphinus delphis), risso’s dolphin (Grampus griseus), rough-toothed dolphin (Steno bredanensis), atlantic spotted dolphin (Stenella frontalis), guiana dolphin (Sotalia guianensis), false killer whale (Pseudorca crassidens), killer whales (Orcinus orca), long-finned pilot whale (Globicephala melas) and sperm whale (Physeter macrocephalus) were seen interacting with plastic objects.

Unfortunately, evidence of cetacean play with plastics is recorded in only three peer-reviewed studies (Figure 1c), which showed a rough-toothed dolphin, a long-finned pilot whale, and a risso’s dolphin interacting with plastics.

On the other hand, 34 events on social media websites documented eight different species of toothed whales “playing” or “potentially playing” with plastic litter. The majority were bottlenose dolphins with 41%, followed by spinner dolphins with 35%, as illustrated in Figure 1b.

Most interactions were captured in the Atlantic, followed by the Pacific, Red Sea and Mediterranean (Figure 1a). The Canary Islands, as well as Madeira and Azores, showed most interactions of this kind, whereas most cetacean interactions with plastics in the Pacific were recorded in Hawaii.

Cetaceans mostly interacted with single-use plastics (SUPs), such as sheetlike items, plastic bags, and leftover raffia sacks (Figure 1d). The colour of these plastics was mainly white and transparent. Playful behaviour with plastics was largely captured on pictures and to a less extent on video.

Figure 1. a) Number of records per ocean basin where cetaceans have been reported to interact with plastic including all the events registered in social media, peer-reviewed literature, and the case study; b) species of cetaceans documented to interact with plastic litter; c) the number of records found over the years on the social media and scientific literature; and d) plastics typologies by shape and colours (Rodriguez et al., 2023)

Whales and dolphins touched plastics mostly with their head (melon and beak), followed by their dorsal fin, pectoral fin, and fluke (Figure 2). In some cases, individuals would move plastic items between body parts. When plastic items slipped off during contact, some would be eager to return to interact with it again. Some individuals would even throw plastics out of the water, suggesting play.

Figure 2. Examples of bottlenose dolphins (a-c), common dolphins (d), sperm whales (e), and risso’s dolphins (f) interacting with SUPs such as plastic bags or sheetlike items in the NE Atlantic. (Photo credit: Futurismo – Azores Whale Watching, in Rodriguez et al., 2023)

The curious case of cetaceans and plastic pollution

Most cetaceans play with plastic items out of curiosity, and this may be a key factor in subsequent entanglement and plastic ingestion. Ingesting plastics can lead to physical blockages, disruption of regular food intake, or starvation due to a false feeling of abdominal fullness. Sperm whales have been reported having high quantities of SUPs in their gastrointestinal tracts. Likewise, autopsies in dolphins have revealed micro and macroplastic content.

Cetaceans playing with marine litter is an unnatural behaviour and has severe impacts on their overall health and wellbeing. Dolphins playing with plastics are bad role models to nearby calves (Figure 2a). More than sixty countries have implemented bans and regulations on SUPs, but effective strategies to ultimately reduce consumption are not addressed. This study should further people’s awareness regarding marine pollution and encourage them to reduce consumption and to mitigate the ecological impacts caused by them.

Cover image: Figure 3 in Rodriguez et al., 2023: Two bottlenose dolphins: one interacting with a black plastic bag (left) and the other being entangled around the head (right).

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