Marine Mammal Health Map


Photo: The Marine Mammal Center

The goal of this project ("Marine Mammal Health Map") is to develop a national marine mammal health tracking program that is web-based and readily accessible to scientists, managers and the general public. This will allow detection of spatial and temporal changes in marine mammal health that will enable early prioritization of management and conservation efforts to mitigate mortality and identify potential public health risks. In addition, this project will potentially contribute to the detection of climate change impacts on marine mammal health.

Why track marine mammal health?

There is a need for a national marine mammal health tracking program that will allow detection of spatial and temporal changes in animal health. A review of the status of marine mammal research in 2003 (Reeves and Ragen 2004) concluded that a more coherent and comprehensive infrastructure was needed to investigate marine mammal health in a systematic and holistic manner. In 2004, the U.S. Commission on Ocean Policy stated that a sustained and appropriately funded response and analysis program could help identify causes of marine mammal strandings, and actions to prevent further deaths. The 2012 IOOS summit included a Community White Paper highlighting this need for a marine mammal health tracking program

Are Changes in Ocean Health Reflected in Marine Mammal Health?

An increase in the reporting of diseases in marine organisms has raised concerns that ocean health is deteriorating (Harvell et al. 2004, Gulland and Hall 2007). Diseases can alter mammal population distribution and abundance, may ultimately result in species extinction, and can cause major regime changes within marine communities (Kim et al. 2005). However, whether the increase in reports represents a real and widespread degeneration in the health of marine mammals is unclear (Lafferty et al. 2004). This uncertainty is due to a lack of information on the true incidence of marine mammal diseases and few long term datasets. These issues are caused by the lack of specific and directed marine mammal health monitoring, as well as a lack of data integration across taxa (Kim et al. 2005). Richardson and Poloczanska (2008) argued that the dearth of documented changes in marine systems associated with climate change is an artifact of the distribution of global science funding, the difficulty of disentangling multiple stressors from poorly sampled systems, and the way marine ecologists report research findings, amongst other factors. This is exemplified in the scarcity of readily accessible data on marine mammal mortality events, health status and distribution of pathogens, toxins and pollutants in marine mammals.

Marine Mammal Health, Public Health and Climate Change

Despite this lack of long term marine mammal health data, there is considerable interest in marine mammal health and there are existing sampling and response programs. Marine mammal die-offs attract high levels of public attention, as well as concern over human safety in areas of the die-offs. Among marine animal diseases, the majority (60% in one survey) of emerging infectious diseases are zoonotic (transmissible to humans) (Patz et al. 2011). Non-infectious disease, such as toxicoses from exposure to harmful algal blooms or pollutants, can also affect human health and food safety, as well as marine mammal health. The concept of One Health, that human and animal health are intimately associated and both are affected by environmental changes, is becoming widely accepted and needs to be extended from the terrestrial realm to the marine environment (Patz et al. 2011). Furthermore, climate change will likely have both direct and indirect effects on marine mammal diseases by changing pathogen survival, host and pathogen distributions, and host susceptibility. Detection of these changes will require baseline data and a coordinated health tracking program (Burek et al. 2008). Hence, it is crucial to reevaluate how data on marine mammal health are collected and integrated so a true understanding of health changes can be developed. Understanding the temporal and spatial distribution of different marine mammal health changes nationally will allow identification of hot spots. for disease outbreaks and health changes, which in turn will allow prioritization of management efforts to mitigate impacts on marine mammal health.



Pilot Project to exemplify marine mammal health data available in the U.S.: California sea lion (Zalophus californianus) strandings associated with domoic acid toxicosis.


California sea lion suffering from domoic acid toxicosis.
Photo: The Marine Mammal Center

Domoic acid (DA) is a marine biotoxin produced by some diatom species of the genus Pseudo-nitzschia that appear to be becoming more frequent along the West Coast of the United States. This is a concern for marine mammal health because DA is an excitatory amino acid that has a high affinity for glutamate receptors that are present in the mammalian central nervous system and heart. The interaction of DA and these glutamate receptors causes cell depolarization, dysfunction and death, resulting in seizures, epilepsy, cardiomyopathy and death depending upon the ingested dose. In humans, DA is the cause of a neurotoxic illness termed amnesic shellfish poisoning (ASP), first recognized in Canada in 1987 following consumption of contaminated shellfish. In marine mammals, DA toxicosis is best documented in California sea lions (Zalophus californianus) that develop severe neurological signs including epilepsy associated with acute and long term effects of DA exposure. Lesions in affected sea lions include neuronal necrosis in the hippocampus, which may progress to hippocampal atrophy, and degenerative cardiomyopathy. California sea lions have stranded along the California coastline over the last 15 years due to DA toxicosis. This species appears to be the most commonly affected marine mammal in California, presumably due to a combination of foraging behavior and seasonal movements. Location of California sea lion strandings associated with DA toxicosis can provide insight into the location of DA-producing blooms, and highlight areas for more intensive water sampling to monitor these blooms.


Map animated through time to show the stranding locations of California sea lions that were admitted to The Marine Mammal Center from February 1998 to May 2013 with DA toxicosis that died or were euthanized.


Stranding location of California sea lions that were admitted to The Marine Mammal Center from February 1998 to May 2013 with DA toxicosis that died or were euthanized.


Number of California sea lions that were admitted to The Marine Mammal Center from February 1998 to May 2013 with DA toxicosis that died or were euthanized.

Contact Information

Frances Gulland or Tenaya Norris
The Marine Mammal Center
2000 Bunker Road, Sausalito, CA 94965


Frances Gulland with a massive tail fluke.
Photo: The Marine Mammal Center

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