Ingestion of Marine Debris and Sperm Whales

By Jessica Daley, SRC intern

Marine debris is one of the greatest threats facing marine life today. Any man-made, produced, or processed material that is either intentionally or accidentally discarded and finds its way to the ocean is considered marine debris. There are two major hazards to marine life from interactions with debris, entanglement and ingestion (Jacobsen et al. 2010). Entanglement occurs when an animal becomes trapped or wrapped in marine debris and is unable to escape. In some cases this involves discarded nets and other fishing gear, which can ensnare nearby marine life. This is especially dangerous for marine mammals, which breathe air and can drown if they are unable to free themselves (Jacobsen et al. 2010). Some entanglement cases are not lethal, but still severely damage the animal. For example, if a young turtle becomes trapped in a soda-case ring, it may not cause any problems at first. As the turtle grows, however, the ring becomes tighter and tighter on the body, warping the shell and potentially damaging internal organs.

A turtle trapped in a plastic soda ring has grown around the debris, warping its shell. [Leijon, Stefan. “Plastic Turtle.” 29 July 2012.]

Ingestion of marine debris can also be extremely dangerous for sea life. It is not uncommon for dead sea turtles to be found with plastic in their stomachs, because plastic bags resemble the jellyfish that several turtle species feed on (Mascarenhas et al. 2004). Blockage and rupture of the digestive systems are sometimes causes of death, while in other cases the animal starves to death because plastic has no nutritional value but takes up space in the stomach (Mascarenhas et al. 2004).

In the winter of 2016, a study was conducted by Unger et al. on the marine debris found inside 22 sperm whales that stranded and died along the coast of the North Sea (in England, France, the Netherlands, Germany, and Denmark). Prior to this study only 17 cases of debris ingestion had been noted in sperm whales (Unger et al. 2016). Sperm whales are deep-water animals, feeding mostly on squid at depths of more than 1000 meters, but must return to the surface to breathe (Unger et al. 2016). Because they live so deep, it is uncommon for sperm whales to strand. The North Sea is a shallow and variable habitat that is far from ideal for the sperm whale, and has a comparatively high stranding rate on its shores (Unger et al. 2016). Between January 8th and February 24th, 2016, a total of 30 sperm whales stranded along the North Sea. Of these, 22 whales had their gastro-intestinal tracts opened and examined during their necropsies. Seven GTIs were then rinsed and sieved to look for evidence of smaller debris bits. Fecal samples were also taken from 12 of the whales to look for evidence of micoplastics. The thickness of the whales’ blubber was also measured to assess nutritional status.

Nine of the 22 whales were found to have marine debris in their GI tracts, for a combined total of 322 pieces of trash. Of the debris found 78% was assorted fishing gear, including nets, hooks, monofilament fishing line, and rope. The remaining 22% was considered general debris, or anything that was not fishing related. Among the items discovered were a chocolate wrapper, a plastic bucket (broken in half), and a plastic car engine cover. It could not be determined that debris in any of the whales was the cause of death, and all of the whales were found to be in good overall nutritional health. No GI tract lesions or other internal injuries were observed either.

A large net inside the stomach of one of the stranded North Sea sperm whales [Ungar et al.]

A collection of all of the debris found inside a single whale [Ungar et al.]

The high percentage of the whales that had debris in their GI tracts as well as the high number of individual items suggests that sperm whales are more likely to ingest marine debris than other species, but it is not clear if the high volume of trash is partially due to the lack of sperm whales’ normal food source, deep water squids, in the North Sea (Unger et al. 2016). In the 100 years prior to this study only 17 sperm whales had been found with debris in their stomach, and it was assumed that marine debris was of minimal threat to sperm whales. With the results from this study, that proposition appears to be untrue. Although none of the whales showed signs of internal injuries or other complications from the debris inside them, the sheer quantity of material as well as the kinds of debris found are significant reasons for concern. It is not unlikely that if the whales had survived, the debris would have led to complications, such as fishhooks puncturing GI tract lining or netting blocking part of the tract (Jacobsen et al. 2010). In 2008 two sperm whales that stranded in northern California were found emaciated and with a significant amount of debris in their stomachs. One of them also had a ruptured stomach, and the cause of death of both whales could be traced back to the foreign material, which supports the assertion that ingestion of marine debris is dangerous to large cetaceans (Jacobsen et al. 2010).

There is a tremendous amount of evidence that demonstrates how dangerous marine debris is to sea life because of potential entanglement and ingestion. The most effective way to help protect these animals is to limit the amount of trash that enters the ocean, as well as attempting to remove what is already there. The United States alone produced 254 million tons of trash in 2013, and some of that trash inevitably ends up in the ocean (EPA). If you are interested in helping to decrease the amount of debris in the oceans there are many things you can do. Limiting your single-use plastic usage is perhaps the most impactful thing you can do, by doing things like using reusable shopping bags, using metal silverware instead of plastic, not using plastic straws, and using a reusable water bottle (Smithsonian Ocean Team). Beach clean-ups are a great way to help prevent coastal trash from making its way to the ocean. If you are a fisherman, you should avoid cutting and losing nets and monofilament lines so that do not become a potential hazard to animals (Smithsonian Ocean Team). While they may seem like small contributions, they can make a major impact on the lives of marine creatures.

Works Cited

Jacobsen, Jeff K., et al. “Fatal Ingestion of Floating Net Debris by Two Sperm Whales (Physeter Macrocephalus).” Marine Pollution Bulletin, vol. 60, no. 5, 2010, pp. 765–767.

Mascarenhas, Rita, et al. “Plastic Debris Ingestion by Sea Turtle in Paraı́ba, Brazil.” Marine Pollution Bulletin, vol. 49, no. 4, Aug. 2004, pp. 354–355.

“Municipal Solid Waste.” EPA, Environmental Protection Agency,

Smithsonian Ocean Team. “How You Can Help the Ocean.” Ocean Portal | Smithsonian, Smithsonian’s National Museum of Natural History, 27 Dec. 2017,

Unger, Bianca, et al. “Large Amounts of Marine Debris Found in Sperm Whales Stranded along the North Sea Coast in Early 2016.” Marine Pollution Bulletin, vol. 112, no. 1-2, 2016, pp. 134–141.

Individual, unit and vocal clan level identity cues in Sperm Whale Codas

By Ryan Keller, SRC intern

The social calls produced by sperm whales consist of three or more broadband overlapped clicks, called Codas. It is believed that certain codas are used to call certain individuals within a unit rather than a broader class of codas which are to all whales in the area. During social learning whales will “babble” and produce many indistinct codas before mastering the skill and eventually producing the specific calls much like a human baby making noises before learning specific words. In order to know what message each specific coda transmits further research needs to be done. By observing social interactions and behavior while simultaneously identifying what codas are being produced it should make their meanings evident.

As seen above, a Sperm Whale (Physeter microcephalus) breaching. The head of the sperm whale contains a waxy like substance called spermaceti which it uses to focus and amplify the clicking noises used for communication and echolocation.

As seen above, a Sperm Whale (Physeter microcephalus) breaching. The head of the sperm whale contains a waxy like substance called spermaceti which it uses to focus and amplify the clicking noises used for communication and echolocation. Source: Wikimedia commons. 

Gero et al. (2016) examined codas of sperm whales in the Caribbean, focusing on male and female social groups. The study took place along a 2000km2 area along the coast of Dominica over winters from 2005-2010. Acoustic recordings of echolocation clicks made during dives as well as the codas produced at the surface when the whales. By comparing certain aspects of the echolocation clicks and comparing them to the codas they were able to assign the codas to the specific animals that were making them. They identified over 70 different types of codas with the ones containing 4,5 clicks to be the most common.

It appears that the whales will make these sounds in a duet like fashion and mostly during social interactions or at the surface, not when they are deep hunting for food. Males live most of their lives in solitary while females may travel in groups of two or more called “units”. These units have similar but distinct dialects of codas. This causes segregation between different units as they will only associate with each other if they have the same dialect.

Pictured above: a mother Sperm Whale and her calf swim near the surface. Sperm whales have complex social hierarchies and communicate using various clicking noises called codas

Pictured above: a mother Sperm Whale and her calf swim near the surface. Sperm whales have complex social hierarchies and communicate using various clicking noises called codas. Source: Wikimedia commons.

Social interactions and communication is most complex and through with primates, especially humans. We are just starting to fully understand just how complex many other species social structures are. More research is needed to figure out the specifics of codas and what each one means. We have always just assumed that we are the only species with a language and dialects but it seems that we may not be alone when it comes to this complex and arguably most important social tool.


Gero S, Whitehead H, Rendell L (2016) Individual , unit and vocal clan level identity cues in sperm whale codas. Royal Society Open Science, 3, 1–12.