Whales, dolphins, and seals aren’t just charismatic ocean dwellers—their complex social lives could be a hidden vulnerability when it comes to disease outbreaks. A new global study reveals that understanding how marine mammals interact is crucial for predicting and managing illnesses in a changing ocean environment.
Table of Contents
Understanding the social connections of whales and dolphins is vital for protecting them from widespread illness, especially as oceans face increasing threats.
- Infectious disease is a leading cause of death for marine vertebrates, alongside human impacts like fishing and pollution.
- Highly connected individuals within marine mammal populations can act as “super-spreaders” of disease.
- Monitoring social networks can help identify vulnerable populations and provide early warnings of outbreaks.
- Protecting habitats that support stable social structures may reduce disease transmission.
In a new global study, marine mammal experts warn of the potential for pandemics in marine environments, with some species facing greater risk than others. Associate Professor Guido J Parra from Flinders University emphasizes that infectious disease transmission in marine mammals is a relatively understudied area, yet it poses a significant threat to more than a quarter of species currently classified as threatened.
“Disease is one of the leading causes of mortality in marine vertebrates, along with fisheries interactions, pollution, habitat degradation and climate change,” says Associate Professor Parra from the Cetacean Ecology, Behaviour and Evolution Lab (CEBEL) at Flinders University. “These stressors tend to weaken immune systems and make animals more vulnerable to infection.”
Just like humans, marine mammals rely on social networks, and diseases readily move through these connections. Effective conservation strategies require a deep understanding of how these networks differ between species and how they interact.
The Challenge of Studying Disease in the Wild
PhD candidate Caitlin Nicholls, with the CEBEL research group at Flinders’ College of Science and Engineering, explains that dolphins, whales, and seals are inherently social creatures. Many live in groups, forming lasting bonds with preferred companions, while others navigate fluid, ever-changing social networks.
“Unlike on land, scientists cannot easily observe every interaction, isolate sick individuals, or intervene early when disease begins to spread,” says Ms Nicholls, lead author of a new article in Mammal Review. The research utilized decades of historical data to model species behaviors and map social connections and patterns.
The study revealed that highly connected individuals often play a disproportionately large role in disease spread, acting as “super-spreaders” who can rapidly transmit infections throughout a population. In dolphin communities, for example, animals with stronger or more frequent social ties are more likely to be associated with disease.
While bottlenose dolphins are among the most studied species—particularly in Australia and North America—many threatened species and other regions remain poorly understood, limiting our ability to assess and manage disease risk.
What makes marine mammals particularly vulnerable to disease outbreaks? The combination of social structures, environmental stressors, and the difficulty of intervention creates a perfect storm for rapid disease transmission.
Prevention and Early Detection are Key
Researchers emphasize the importance of proactive wildlife health monitoring and management. Marine mammals are often difficult, if not impossible, to treat once a disease is widespread.
“Prevention, early detection and informed management will be critical, particularly for the most vulnerable populations before an outbreak makes animals sick,” adds Associate Professor Parra. “Understanding social relationships can help identify which individuals or populations are most vulnerable before an outbreak occurs.”
Targeting monitoring efforts towards socially central animals could provide early warning signs of emerging diseases. Protecting habitats that support stable social structures may also help reduce transmission risk.
Modes of transmission include direct contact, airborne/respiratory, bites or wounds, and sexual activity. Diseases affecting marine mammals include viral, bacterial, fungal, and protozoal infections such as Papillomavirus, Poxvirus, Morbillivirus, Influenza, Herpesvirus, Caliciviruses, Lobomycosis, Brucellosis, and Toxoplasmosis.
The article, ‘Sociality of marine mammals and their vulnerability to the spread of infectious diseases: A systematic review’, (2026) by Caitlin R Nicholls, Mauricio Cantor (Marine Mammal Institute, Oregon State University), Luciana Möller and Guido J Parra has been published in Mammal Review DOI: 10.1111/mam.70020.
