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Ally Breen, Dana Littlefield, Corey Logan, Iris Morin, and Katie Quinn-Cyr

Abstract

Sperm whales are a staple of marine life, known for their intellect and impressive size. However, like all animals, they have been negatively affected by modern human interference. One example of this would be the Great Pacific Garbage Patch, a large mass of plastic floating in the Pacific Ocean as a result of ocean currents and unsustainable recycling methods. This chapter will dive into greater detail on sperm whales, the threats they face, and the ways that their populations can be protected and maintained.

“A pod of sperm whales off the coast of Mauritius” by Gabriel Barathieu is licensed under CC-BY-SA 2.0

Natural History and Physical Description

With their intelligence and affinity to exist in a life-long family, sperm whales (Physeter macrocephalus) are goliath marine mammals that have affectionately gained the reputation as the “elephants of the sea.” As seen in Figure 1, their gray bodies, with relatively small, white sections on their underside, waxy skin, and slight wrinkles on their heads uniquely characterize this species. Their blowhole, located on the left side of their head, adds to their unique features. Their small, paddle-shaped fins are located halfway back on their bodies, and their dorsal fins are low, wide, and rounded. Their heads are extremely large and make up an astounding one-third of their body length. Their thin, long jaws contain between 10 and 26 teeth on each side (NOAA 2021). A sperm whale will use its teeth to prey on deep-sea organisms such as squid, sharks, skates, and other fish, diving up to 10,000 feet below the surface for an average range of 45-60 minutes. Sperm whale’s, typically weighing 15 tons to 45 tons, consume about 3.5% of their body weight each day (NOAA 2021).

Figure 1: “Size comparison of a male and female sperm whale with a human (16m, 11m, 1.75m respectively)” by Kurzon licensed under CC BY-SA 3.0 

These creatures may be an impressive sight, but they are not immune to threats within their ecosystem. The main factors that lead to the premature demise of these ‘elephants of the sea’ are unfortunately all too common for these majestic creatures. These threats include but are not limited to, vessel strikes, ocean noise, marine debris, climate change, and oil spills, and contaminants (NOAA 2021). For a population historically depleted by whaling, these threats are detrimental. The National Oceanic and Atmospheric Agency (NOAA) estimates that, since the whaling moratorium went into effect in 1986, the sperm whale population has only grown about four percent per year (Alaska Fish and Game). This slow growth rate makes any loss to the already small population devastating.

The small growth rate of sperm whales is primarily due to their life cycle and survivorship behavior. Sperm whales exhibit sexual dimorphism, meaning that males and females exhibit different physical characteristics. A female will grow to 40 feet in length and weigh up to 15 tons, whereas a fully grown male can be around 52 feet in length and up to 45 tons in weight. The female begins her life cycle in rapid growth for the first 9 years of age, at which point she will reach sexual maturity and see slowed growth. She may be ready to produce a calf at 9 years old, yet a single calf is only produced every 5-7 years. This slow rate of reproduction, along with a gestation period of 14 to 16 months, contributes to the slow growth rate (NOAA 2021).

In comparison to their female counterparts, the male sperm whale’s growth and puberty period last much longer. In fact, male sperm whales may experience puberty up until the age of 20. Even in the case of a male reaching sexual maturity, he may not participate in breeding until his late 20’s regardless. However, the differences after this age are relatively minute. Both females and males form social units or pods called stocks, and as males get older they will depart the pod and typically travel alone toward the poles while the females stay in their pods near the equator at a common breeding ground (NOAA 2021).

Sperm Whale Distribution

With the exception of the poles, sperm whales can be found all across the world’s oceans. This wide distribution is shown as blue in Figure 2. Scientists were able to use biochemical markers, such as the gene CYP1A1, nitrogen and carbon isotope ratios, latitude, and whale blubber contaminants to determine areas of the Pacific Ocean where sperm whale populations were highly concentrated (Godard-Codding et al. 2011).

Figure 2: Sperm Whale distribution in blue. “Sperm whale range map” by NOAA (2021), Public Domain.

Sperm whales are typically found in deep waters, usually avoiding the coastal shelf but staying within a few hundred kilometers of the coastline (Purdon et al. 2020). This concentration pattern can be seen in the heat map displayed in Figure 3.

Figure 3: Coastal heat map of sperm whales in summer (G) and winter (H) shown in the bottom panels. “Ensemble model projection using the mean probabilities for each season for the Bryde’s whale, humpback whale, southern right whale and sperm whale” by Purdon et al. 2020, CC BY 4.0

Despite its widespread distribution, sperm whales tend to stay with their stocks. This affects the population’s genetic characteristics as well as behavioral patterns, which influences conservation efforts for different stocks of sperm whales (Begg and Waldman 1999). Stocks tend to contain anywhere from 10 to 14 whales that, depending on the stage of the life cycle they are in, will have a similar age range or family structure. The unique patterns exhibited by different stocks or populations, depending on the region in which they live, create very different migration patterns that are not easily or well understood. Food sources, breeding grounds, and water temperature all contribute to the specific behaviors of individual populations, as well as the global distribution of sperm whales on a yearly basis. Due to their extreme diving behavior, the seasonal migration of the sperm whale is also difficult to track in comparison to most other species.

Sperm Whale Ecological and Social Impact

As a keystone species, sperm whales play monumental roles in ocean health and greatly impact the overall stability of marine ecosystems. The diet of a sperm whale consists of large fish and invertebrates, which places their species high on marine trophic levels, below only orca whales and the largest of sharks (Safina 2016). Their ability to contribute to carbon and nutrient cycling in the ocean through natural behaviors makes all whales excellent ecosystem engineers. Each time a sperm whale dives at depths of up to 10,000 feet, they are actively mixing the marine water columns and agitating nutrients and minerals to enrich the entire ocean ecosystem around them (Animal Welfare Institute 2017). Sperm whales encourage carbon sequestration by aiding the growth of phytoplankton populations, which absorb atmospheric carbon dioxide. Sperm whales do this via the nutrient release from their fecal matter, which enhances the productivity of the phytoplankton at the ocean surface. As the carbon dioxide-rich matter sinks to the ocean floor, it will successfully trap 20 to 40% of the carbon for millennia. The remaining carbon will continue to circulate marine life at the ocean’s surface. This sperm whale-driven system successfully removes 240,000 tons of carbon from the atmosphere per year and provides a significant ecosystem service (Animal Welfare Institute 2017). Even after death, whales facilitate marine life with a biological event called a “whale fall”, in which a whale dies and its body sinks to the ocean floor to decompose. A single whale fall event can provide food and nutrients for over 400 deep ocean species in the vicinity for up to a decade, as well as sequester massive amounts of carbon (Safina 2016).

The sperm whale has even provided intellectual services in areas such as religion, the arts, cultural unity, identity, and modern education (Cook et al. 2020). Whales have had a growing impact on art and music since 1970 and have been the center of important media throughout the years, such as in the book Moby Dick (Cook et al. 2020). In certain regions, whales have been cemented in the founding culture of modern civilization. Whales can be found throughout the myths, legends, and religions of older civilizations, such as the indigenous people of Canada, New Zealand, and Hawaii (Cook et al. 2020). In Polynesian culture, sperm whales are sacred, and their teeth and bones are believed to be a symbol of good luck. As a result, their artifacts are sold and traded for valuable art and jewelry, but the materials are only collected from the sperm whales after they have already died and washed ashore. A treaty developed in Tonga has made it illegal to kill whales or even trade goods that have come from whales (Van der Grijp 2007). Sperm whales are a key factor to maintaining biodiversity and species richness in their marine ecosystem and contribute to our understanding of ethics from an educational standpoint in modern times.

The modern whaling industry, both commercial and subsistence, has societal and ethical implications and consequences. The commercial needs have grown in recent years to unsustainable demands, with countries such as Norway and Japan ravaging the whale populations (Scheiber 1998). This is agreed upon as unethical by the standards of modern environmentalism, as these industries favor profit over the well-being of whale populations and the biodiversity of ocean ecosystems. While wasteful commercial industries ravage the whale population, indigenous people take only as much as needed and utilize the whole whale through subsistence practices (Scheiber 1998). The ethical implications carry more weight when applied to larger companies. While indigenous communities with deeply rooted ties to whaling in their cultural practices take advantage of the entire whale so as to avoid being wasteful, industries typically only use some of the whales and discard the rest as it is considered to be worthless (Scheiber 1998). The ethical implications are important considering humanity’s large-animal bias. If sperm whales are recognized as having dignity, then that thinking may extend to other smaller or overlooked organisms in the future. The intelligence of sperm whales has sparked important moral and ethical debates. Their ability to communicate and echolocate has supported their sympathetic appeal, which attracts society to supporting conservation efforts (Kalland 1991).

In the 19th century, sperm whales were hunted for their spermaceti organ which was used for illumination oils.  As demand for illumination oils increased, more whaling occurred (Kaiser 2013). However, the opportunity cost rose quickly because it became harder to find whales as populations dwindled, which in theory was accounted for by a drastic increase in the price of spermaceti oil. The economics of whaling eventually transferred from over-predation to popularizing conservation efforts (Kaiser 2013).

Sperm whale depredation has also had socio-economic consequences for fisheries. Longline fisheries in particular have suffered direct costs, such as catch losses, and indirect costs, such as increased fishing time or fuel consumption, as a result of depredation by sperm whales (Janc et al. 2018). Depredation has caused a need for fishing industries to reevaluate fishing equipment and conditions of fishing operations. Although fishing industries are looking to implement technological solutions to deter depredation and lessen the economic consequences they face. One important factor of sperm whale conservation is the overexploitation of fish populations. This raises the question of how we should manage natural resources and to what extent we should utilize these resources for ourselves versus wildlife populations.

Impacts of Plastic Pollution on Sperm Whales

Possibly the most unlikely, yet deadly predator of marine life in today’s world is ocean plastic pollution (Johnson 2021). These bits and pieces of garbage can be found in every part of the world’s oceans at all depths, and the marine ecosystem is feeling its effects. The current estimate of surface plastic pollution is 269,000 tons, while the annual global input is between 8 and 11 million tons (Ritchie 2018). One might not expect a creature as large and powerful as a sperm whale to be affected by ocean plastic, yet ocean pollution is becoming their greatest threat. The two main ways ocean pollution harms marine life are through ingestion and entanglement, and for sperm whales, there is no exception.

Ingestion of plastic is a very serious problem for all whale species. Plastic pollution ranges from large fishing nets to tiny particles called microplastics. Sperm whales will typically ingest larger marine debris, mistaking it for the larger prey they feed on. While sperm whales do ingest microplastics, the effects from the released chemicals are small compared to impacts from larger debris. A whale can survive after ingesting a few pounds of plastic but will be constantly experiencing the effects of starvation and stomach unrest (Johnson 2021). It is hypothesized that large amounts of ingested plastic could be causing whale species to intentionally beach themselves to escape inevitable starvation. Sperm whales have been found all over the world beached with pounds of marine debris in their stomachs. Two sperm whales were found on the northern coast of California with 53 lbs and 162 lbs of plastic, rope, and net debris in their systems, as seen in figure 4. It was suspected that both animals died from gastric rupture as a direct result of the ingested pollution (Jacobsen et al. 2010).

Figure 4: “Dead sperm whale found with pounds of garbage in its stomach, including rope, plastic and fishing nets”. Used with permission from The Scottish Marine Animal Stranding Scheme

It is possible that these poor creatures had encountered most of this trash while in the Great Pacific Garbage Patch (GPGP) located off the coast of California, and some whale sightings in this region can be seen in Figure 5. The GPGP is the largest ocean pollution gyre in the world with an estimated surface area of 617,763 square miles (The Ocean Cleanup 2019). Due to the abnormally high percentage, 46%, of the GPGP being discarded fishing nets, commonly known as “ghost nets,” entanglement is a huge concern for sperm whales moving through that area of the ocean (The Ocean Cleanup 2019). This is considerably concerning, as ghost nets engender 300,000 cases of whale, dolphin, and porpoise deaths by means of starvation, exhaustion, or suffocation every year (Johnson 2021).

Figure 5: “Cetacean sightings within the Great Pacific Garbage Patch” by Gibbs et al. 2019, CC BY 4.0

Current Conservation

Right now, sperm whales are not a globally protected species, but they are protected by various conservation efforts and protective methods. Sperm whales are active on two lists of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and have been categorized as “in danger of extinction” throughout all or most of their range. The species’ poor conservation status might be improved if an international co-operation agreement could be organized (DSWP 2021).

In the Caribbean, sperm whales are protected by the Specially Protected Areas and Wildlife Protocols (SPAW). There are current regulations in place for whale-watch tours to ensure proper guidelines are being followed, as well as efforts to enforce a protected marine area (DSWP 2021). In the Mediterranean Sea, there is also the ‘Protocol for the Protection of the Mediterranean Sea against Pollution from Land-Based Sources and Activities’, and the ‘Protocol for the Protection of the Mediterranean Sea against Pollution Resulting from Exploration and Exploitation of the Continental Shelf and the Seabed and its Subsoil’ that protect sperm whales and other marine species from pollution (Notarbartolo-di-Sciara 2013). Finally, the International Whaling Commission has implemented regulations for the management of sperm whale populations (IUCN 2008). The unique and poorly understood qualities and patterns of sperm whale populations around the globe require several specified protection efforts in different locations for maximum effectiveness. However, the current conservation efforts aim to protect a historically overexploited species with natural barriers that prevent the population numbers from increasing significantly. Plastic pollution, especially in the case of the GPGP, has come to a point where conservation efforts are aimed toward fixing a human-made problem, and their effectiveness has not proved to be very significant so far.

Furthermore, recent data suggests that the Great Pacific Garbage Patch is growing exponentially in size, currently weighing an estimated 79,000 tons (Fossi 2020). There has been some success with partnerships between private-owned companies funding nonprofit organizations’ cleanup efforts. For example, Project Kaisei is a nonprofit organization working to clean up the Great Pacific Garbage Patch, with an annual goal of removing 50 tons of plastic from the ocean to be converted into renewable energy (Sesini 2011).

Sperm Whale Status

Even after every conservation effort to date, the sperm whale’s current status is listed as vulnerable on the global IUCN Red List of Threatened Species, while The United States Endangered Species Act has sperm whales listed as ‘Endangered” (DSWP 2021). This low rating shows how greatly the whaling industry has impacted sperm whale populations for decades, even after whaling was banned. Current populations collected from a series of surveys ranging from 1996-2007 show an estimate of 30,000 individuals in the Northeast Atlantic. However, as there is limited overlap in the key survey areas and there is likely a negative bias due to sperm whale diving behavior, this estimate is most likely quite conservative (Pike et al. 2019). This is compared to an estimated total population of 300,000 sperm whales worldwide (Shirihai and Jarrett 2006).

Future conservation

Sperm whales have established their importance in marine ecosystems, and we are responsible for maintaining that role and protecting vulnerable species. So how do we continue to manage sperm whale populations? To combat the threats posed to sperm whales by the fishing industry, we would need to implement and monitor fishing regulations and establish swift and effective prosecution against illegal fishing practices. But we should not stop there; we can also go straight to the source itself. Establishing protocols to avoid plastic pollution in marine ecosystems in the first place can lower the risk of the species contacting or ingesting micro and macro plastics. Working toward economically viable recycling practices, while a difficult task, may aid in reducing plastic pollution in the oceans. A more difficult problem to address, however, is incidents of sperm whale collisions with vessels. Restricting maritime travel to designated shipping lanes, limiting the speed at which vessels can travel in areas with a high density of sperm whales, and spreading awareness to captains to have caution when traveling through these populated regions can contribute to a decline in incidents of whale collision with vessels. Broadcasting cautionary messages through VHF radio or including warnings in nautical charts can bring awareness and hopefully save sperm whale lives (Notarbartolo-di-Sciara 2013).  Increasing the number of specified protected areas can help to mitigate many of the problems mentioned previously as well, but mostly in the case of protecting critical habitats.

Prey depletion and climate change are more difficult ecological threats to address, especially given the species’ slow growth rate (Notarbartolo-di-Sciara 2013). Yet we must also consider the restrictions we face to implement such conservation and management efforts. Large-scale stock assessments in the deep seas need to be completed to better address, and potentially combat, biological and ecological factors in the decline of sperm whale populations. However, many of these assessments are financially and technologically beyond the reach of many countries, which introduces a limiting factor that we cannot quickly or easily overcome (Notarbartolo-di-Sciara 2013).

Figure 6: “Sperm whale mother and calf. Observed on System 001’s first mission” by The Ocean Cleanup, permissions

Is Tourism Funding Conservation Efforts?

As of 2008, 13 million people had participated in whale watching tours across 119 countries nationwide. There has been specific growth in the whale watching industry in Asia, the Pacific, South America, the Caribbean, and Europe, which have surpassed global tourism rates over the course of a decade. In combination with the global shift away from whaling practices, the growing whale watching industry has not only contributed to better sperm whale population maintenance and protection but has also generated $2.1 billion in revenue and has created jobs for an estimated 18,500 people in the 119 countries associated with this report (IFAW 2020).

The International Fund for Animal Welfare (IFAW) is an incredibly important conservation corporation leading the global protection of large marine mammals. They work with whale watching companies all over the world to make sure the health and safety of each species are at the forefront of everyone’s minds. They also maintain strong working partnerships with governments and facilitate public awareness for the benefit of whales (International Fund for Animal Welfare 2020). In 2008, the Australian organization, Economists at Large, used IFAW’s collected data to complete an economic and expenditure report called “Whale Watching Worldwide”. The study reported the total expenditure for whale watching tourists be $2.1 billion US dollars, with 41.4% from ticket sales and the remaining 58.6% attributed to other indirect expenses (O’Connor et al. 2009). While the report by Economists at Large does not explicitly say how much compensation the IFAW received, the fact that they are a nonprofit organization implies that any amount they accumulated over the years was used to fund their work, completing the idea that tourism is helping to finance whale conservation efforts (IFAW 2020). Continuing to promote safe and respectful whale watching practices can fund further conservation efforts, introduce a meaningful relationship between society and the sperm whale, and push for the continued protection of the species.

The Importance of Protecting Sperm Whales 

This majestic and impressive marine species holds a key role in maintaining biodiversity and upholding a stable ecosystem. As a keystone species, the need to protect sperm whales on a global scale is significant. As the depleted global populations face a modern, man-made issue of marine plastic pollution, it becomes clear that we hold an important role in managing sperm whale populations. Current conservation efforts are limited by the slow growth of the global population size, as well as technological and financial barriers that make it difficult to fully understand the needs of the species with its wide range and extreme diving behaviors. Recognizing our role in reducing and cleaning plastic pollution to manage sperm whale populations and other marine life is an important step to take. Continued conservation will take time, effort, money, and respect toward the species. For all they provide, this species certainly deserves it.

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