Marine Mammal Stranding Networks in the 21st Century: Whence and Whither?

Marine mammals stranded ashore have captured human attention for centuries—Aristotle observed over 2000 years ago that dolphins sometimes came ashore for unknown reasons. Indigenous coastal communities from New Zealand to the Arctic have oral histories documenting stranding events (Marsh et al. 2022) and dramatic scenes of dead whales swarmed over by a curious public were recorded by 16th-century Dutch painters (Figure 1). The efforts of visionaries who saw the scientific potential in marine mammals stranded ashore have changed these events from spectacles to sites of scientific endeavor, providing the foundation for ocean biomonitoring programs worldwide. Stranded marine mammals have become recognized as sentinels for the health of conspecifics, their environment, and humans who depend on healthy ocean resources (Reddy et al. 2001). Continued investment in stranding network capacity could further enhance responses to both live and dead stranded animals, improving their welfare, expanding the science of these species, and better informing the “One Health” (an integrated, unifying approach that aims to optimize the health of people, animals, and ecosystem recognizing they are closely linked and inter-dependent) community and management actions for conservation. Formal stranding network responses in the United States date back to 1883 (True 1883) when Frederick W. True (Marine Mammal Curator) and Spencer Fullerton Baird (Director) from the US National Museum of Natural History requested the Light Keepers of Cape Hatteras, NC, record data on marine mammal carcasses. In the United Kingdom, a 1913 agreement between the British Museum and Board of Trade recorded data on cetacean strandings by the “Receivers of Wreck” using a specific form transmitted to the museum by telegram (Fraser 1934). In 1968, New Zealand stranding data held in museums and private records were compiled by Gaskin (1968) to investigate potential causes of mass strandings (see Table 1 for a timeline of stranding network development). In the United States, Dr. James Mead and Mr. Charles Potter began their tenures at the Smithsonian Institution National Museum of Natural History in 1972, when they established the Stranding Event Alert Network “SEAN,” and distributed brochures to ocean users requesting notification of cetacean carcasses discovered along the eastern seaboard from South Carolina to Massachusetts. These activities coincided with the passing of the Marine Mammal Protection Act of 1972 (MMPA) and were the impetus for the first US Marine Mammal Commission workshop on strandings in 1977. The workshop recommended development of regional stranding networks (Geraci and St. Aubin 1979). Over the following 20 years, regional stranding networks were also established in Europe, Asia, New Zealand, Canada, and Central and South America. The morbillivirus epizootics of 1987–1988 that caused strandings of thousands of seals in the United Kingdom and Europe and bottlenose dolphins (Tursiops spp.) along the east coast of the US-motivated governments to respond to strandings in these countries. A few years thereafter federal government-coordinated stranding networks were established in England and Wales in 1990, Scotland in 1992 and the United States in 1994. Over the half century since the passing of the MMPA in 1972 and the international moratorium on commercial whaling in 1982, the responses to stranded marine mammals have advanced. The desire to improve the welfare of live animals ashore, as well as to maximize the science obtained from these animals, led to the publication in 1993 of the first globally recognized manual on how to respond to a stranded animal (Geraci and Lounsbury 1993, revised in 2005). To enhance coordination among responders, regional, national, and international networks have further developed (reviewed by Wilkinson and Worthy 1999; Simeone and Moore 2018). These networks are typically volunteer-led, with varying amounts of government, academic, and private support. A live dolphin ashore is no longer assumed to die, and sea otters, manatees, and pinnipeds have reproduced in the wild after release from rehabilitation (Newman et al. 2003; Yu et al. 2009; Wells et al. 2013; Adimey et al. 2016; Sharp et al. 2016; Neves et al. 2020). Stranding responders have been the drivers of improving marine mammal welfare globally. Stranded animals have provided the basis for numerous scientific advances (see Table 2 for illustrative examples). The body of science that has grown from beach-cast animals is remarkable given the limited funds spent obtaining the information. Response to stranded animals has not only allowed studies of their anatomy, biology, and physiology, but also detected impacts of human activities on their health and survival. For example, fisheries bycatch and entanglement of marine mammals are regularly identified through examination of stranded marine mammals (Friedlaender et al. 2001; de Quirós et al. 2018; Torres-Pereira et al. 2023; Peltier et al. 2024). Gas bubble disease, resulting from exposure to underwater sonar, was identified through investigation of mass strandings of beaked whales (Fernández et al. 2005). That finding provided the information that enabled the Spanish government to prohibit further naval exercises around the Canary Islands in beaked whale habitat (Fernández et al. 2012). The efficacy of the US ship speed reduction rule was associated with a reduction in the number of stranded North Atlantic right whales detected with traumatic lesions typical of vessel strike (van der Hoop et al. 2015), though vessel strikes and entanglement mortalities of North Atlantic right whales continue, Sharp et al. (2019), and require continued monitoring. The impact of the Deep Water Horizon oil spill on dolphin populations in the Gulf of Mexico was assessed through examination of stranded animals, and the results used to guide the fines assessed to the responsible party (Venn-Watson et al. 2015). A suite of toxins, chemicals, and pathogens has been detected in stranded marine mammals, often for the first time in the marine environment (reviews in Gulland et al. 2018). The recent global spread of highly pathogenic avian influenza (HPAI) was detected in marine mammals by sampling stranded animals (Uhart et al. 2024). Mass strandings of baleen whales in Chile and Argentina have highlighted the increases in the extent and duration of harmful algal blooms that poison seafood consumed by both humans and marine mammals (Häussermann et al. 2017), emphasizing the role that understanding marine mammal health plays in the “One Health” concept. Although stranded animals provide opportunities for scientific discovery, disease monitoring, toxin biomonitoring, and assessment of management actions, stranding networks are not achieving their full potential due to a number of limitations. There is still no globally recognized coordination of stranding responses. For example, HPAI recently killed tens of thousands of pinnipeds in South America and has been detected in sporadic cases of stranded seals and dolphins in the United States and Europe (Puryear et al. 2022; Runstadler and Puryear 2024; Uhart et al. 2024). Although this virus is of global concern (having potential to cause a pandemic in humans and kill critically endangered wildlife such as California condors) the lack of a formal global stranding network prevents the efficient, international dissemination of information on virus spread, case detections, and response protocols to stranding responders who could be faced with cases. Instead, communication among stranding responders around the world is dependent upon a few dedicated people working and communicating through a variety of independent organizations. Internationally, the stranding community uses organizations such as the World Organization for Animal Health (WOAH), the Wildlife Disease Association, the Society for Marine Mammalogy, and the International Whaling Commission, among others, for communicating marine mammal disease information, with some stranding responders represented in multiple organizations, and others having no representation. Some countries such as the United States, the United Kingdom, and New Zealand have strong government directives, staff, and/or financial support for stranding responses, but such support can be unpredictable and change depending on their sitting administration's priorities. Other countries, on the other hand, depend upon volunteer private organizations to provide stranding response, care for animals, and collect and synthesize data. The extent of medical care for individual marine mammals, data collection, and public outreach varies among responders due to differing resources, expertise, training, logistical support, and institutional missions. This results in variability in animal welfare, science, and communication of information to managers and the public. This variability limits the ability to broadly apply stranding data to understand threats to marine mammals, such as identifying impacts of human activities (fisheries interactions, vessel strikes, sound impacts, marine debris), documenting the emergence and spread of infectious disease, harmful algal blooms, and environmental contaminants, and detecting effects of climate change on marine mammal distribution and health. Individual responders collect a plethora of data, and some networks have shared databases (reviewed in Chan et al. 2017), yet there is no global meta-database of marine mammal stranding or health information, nor a simple, secure, accessible method to share basic stranding data. This limits the use of stranding data to inform One Health programs and their use in guiding conservation actions. The numbers of reports of stranded marine mammals have increased in most parts of the world in recent years, partially due to increased awareness and communications about stranding events (Simeone et al. 2015). The widespread use of social media has resulted in heightened public awareness, speculations, expectations, and scrutiny of stranding responses. The recovery of populations such as humpback whales (Megaptera novaeangliae) and some pinniped species or stocks, as well as shifts in distribution associated with climate change, has led to a rise in stranding reports due to increased presence of these animals along human-populated coastlines. Increases in vessel traffic, ocean noise, harmful algal blooms, and coastal run-off of pathogens and pollutants also cause more marine mammals to strand (Plön et al. 2024). Caring for and sampling rising numbers of stranded marine mammals increases demands on stranding networks and emphasizes the need for communication and collaboration among responders. The increased reports of stranded animals, advances in live animal care, and continuously growing amount and types of information that are learned from marine mammal strandings are opportunities for enhancing the stranding networks around the world. A single formal international organization with regional chapters dedicated to stranding response could enable rapid communication among members about species, locations, timings, and causes of strandings, and consequently improve communication about threats to both marine mammals and coastal communities. This information could inform managers to enable timely enactment of steps to mitigate risks and protect marine mammals. Table 2 presented here could become a web-based resource updated regularly to maximize use of information from stranding responses. Oliveira et al. (2024) recently outlined how a stranding network could be improved in Brazil to enhance the utility of the data generated for management. Such a vision could be applied elsewhere. For example, for HPAI cases in marine mammals, shared resources could enhance diagnostics and promote timely sharing of response protocols to enhance human and animal protection from the disease. Similarly, information on timing, location, and sources of injury to marine mammals from vessels, fisheries, and other human activities can currently be slow to reach people at local, national, or international levels who could use the information to mitigate activities harming marine mammals. For example, the popular press reported that humpback whale carcasses found along the east coast of the United States in 2023 were suspected to have died as a consequence of offshore wind energy development. This is despite necropsies by stranding network responders identifying lesions typical of vessel strikes in these dead whales, and construction for wind energy platforms had not yet started (Hussain 2024; Thorne and Wiley 2024). A formal pathway for communicating stranding responders' findings efficiently to managers and the public could prevent such misunderstandings. For stranding networks to achieve their full potential, they need the support that comparable organizations dedicated to human (e.g., the World Health Organization, Centers for Disease Control) and livestock health (e.g., WOAH) are given. The formation of a unifying community-led stranding network organization could overcome some of the limitations resulting from varied capabilities of organizations of different sizes and resources and the patchiness in response capabilities. This could influence positive change for marine mammal health and welfare, supporting the alignment of response and animal care practices, standardized data collection, management, and reporting, and the establishment of agreed research priorities in the face of environmental change. Cultural and legal frameworks influencing responses to marine mammal strandings vary around the world, and a unified stranding network community could enhance the standardization of response guidelines to improve animal welfare. The Society for Marine Mammalogy called for increased international capacity in stranding response in the Barcelona Declaration in 2019 (https://www.wmmconference.org/barcelona-declaration). Let us act upon this now and build upon the last half-century of expertise in stranding response to further improve animal welfare and use the science generated from stranding responses to provide for conservation actions. It is time to establish a formal Global Marine Mammal Stranding Network with regional chapters and strong private and public support. We thank the late Drs. Joseph Geraci, David St. Aubin, Bill Perrin, and Sam Ridgway for laying the foundations for stranding response and challenging us to do more; and all the stranding responders around the world who dedicate their lives to caring for stranded animals and ensuring we learn as much as we can from them. Thank you also to the IWC Expert Panel on Strandings for their advice and input on this manuscript. The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.