The Silent Stories of Stranded Cetaceans
How necropsies of marine mammals like the striped dolphin reveal critical insights about ocean health and ecosystem changes
Explore the ScienceIt was an ordinary morning along the Azores coastline when the call came in—a striped dolphin had washed ashore. For most beachgoers, it was a tragic sight; for marine biologists, it was an opportunity.
This sleek, blue-and-white patterned creature, now lying motionless on the sand, held secrets about life beneath the waves that could only be unlocked through careful scientific examination. The procedure about to begin would tell us not just how this individual died, but what its body could reveal about the health of our oceans 5 .
Across the globe, from the volcanic shores of the Azores to the bustling waters of Hong Kong, scientists are performing detailed necropsies on stranded marine mammals.
When a dolphin or whale strands, either dead or alive, it presents a valuable opportunity for scientists to understand aspects of marine biology that are nearly impossible to study in the open ocean. These creatures spend most of their lives hidden beneath the waves, making direct observation challenging. A stranding provides rare access to these elusive animals 4 .
By examining multiple individuals over time, scientists can track diseases, parasite loads, and physiological changes within populations 4 .
As long-lived predators, cetaceans accumulate environmental toxins in their blubber, making them living barometers of ocean pollution 5 .
Parasites can be utilised as markers of environmental changes and fluctuations in parasite diversity may indicate ecosystem distress syndrome 1 .
The Azores archipelago in the Northeastern Atlantic represents a perfect natural laboratory for cetacean research. This remote group of nine volcanic islands serves as a migratory crossroads linking eastern and western Atlantic waters 7 .
Scientists record body measurements, estimate age, evaluate nutritional status, and examine skin for lesions, scars, and parasites 4 .
Each organ is examined in situ before removal. Liver, kidneys, stomach, and intestines are examined for parasites, toxins, and disease 4 .
The heart and lungs are common sites for parasites and infections. Lungs are vulnerable to nematode parasites that cause severe pulmonary lesions 1 3 .
Tissue samples are collected for histopathology, parasitology, toxicology, virology, bacteriology, and genetic studies 4 .
Location: Northeastern Atlantic
Geography: Nine volcanic islands
Marine Significance: Migratory crossroads
Cetacean Species: 20+ species recorded
Research Value: Rich ecosystem with complex topography
| Parasite Type | Location in Host | Significance |
|---|---|---|
| Halocercus lagenorhynchi (lungworm) | Lungs | Causes respiratory lesions; indicator of immune function 1 |
| Anisakis spp. (gastric worm) | Stomach | Can cause gastritis; linked to diet 3 |
| Trematodes | Hepatic bile ducts | Liver function indicator 3 |
| Gammaherpesviruses | Multiple organs including CNS | First reported in odontocete central nervous system 3 |
Perhaps the most significant finding from recent striped dolphin necropsies has been the detection of gammaherpesvirus in the central nervous system. This discovery, made during a mass stranding event in Spain, marked the first time this virus had been identified in the brain and spinal cord of odontocetes (toothed whales) 3 .
"Parasites appear to have a significant impact on the population dynamics of their hosts," potentially affecting survival, reproductive efficiency, and behavior 1 . By compiling data from multiple necropsies, scientists can detect emerging threats to cetacean populations before they cause irreversible declines.
While traditional necropsies remain essential, new technologies are revolutionizing how scientists examine stranded cetaceans. The most exciting development is virtopsy (virtual autopsy), which uses postmortem computed tomography (PMCT) and magnetic resonance imaging (PMMRI) to create detailed 3D visualizations of carcasses before conventional dissection .
Hong Kong has been at the forefront of this innovation, implementing the first Cetacean Virtopsy Stranding Response Programme in 2014. To date, they have performed virtopsies on over 170 stranded cetaceans .
Another technological advancement involves molecular identification techniques. High-Resolution Melting (HRM) analysis allows for rapid, cost-effective species identification using mitochondrial DNA markers 2 .
These molecular techniques don't just identify species—they also help detect and characterize pathogens. In the Spanish mass stranding, nested PCR targeting the DNA polymerase gene allowed researchers to identify previously unknown herpesvirus strains in the stranded dolphins 3 .
Conducting a thorough cetacean necropsy requires specialized equipment and reagents. Below is a comprehensive overview of essential items used in modern marine mammal postmortem examinations.
| Tool/Reagent | Function | Application Example |
|---|---|---|
| Digital Calipers | Precise measurement of lesions, organs, and body features | Documenting blubber thickness as nutritional indicator 6 |
| Histopathology Kit | Tissue preservation for microscopic examination (formalin, cassettes, stains) | Detecting cellular changes in organs 4 |
| DNA Extraction Kits | Isolation of genetic material from tissue samples | Species identification and pathogen detection 2 3 |
| PCR Reagents | Amplification of specific DNA sequences | Detecting herpesvirus infections in stranded dolphins 3 |
| CT/MRI Scanner | Non-invasive internal imaging | Virtopsy implementation for detailed pre-necropsy mapping |
| Liquid Nitrogen Dewar | Flash-freezing tissue samples | Preserving samples for toxicology and genetic analysis 4 |
| Standard Necropsy Kit | Basic dissection tools (scalpels, forceps, bone saws) | Conducting conventional organ examination and sampling 4 |
These tools, combined with standardized protocols, ensure that valuable data is consistently collected from stranding events worldwide, enabling meaningful comparisons across regions and time periods.
The necropsy of that single striped dolphin in the Azores represents far more than an isolated examination. It is part of a global scientific effort to understand and protect marine ecosystems through careful study of their most charismatic inhabitants.
As technological advances like virtopsy and molecular identification become more widespread, our ability to extract information from these natural events grows exponentially.
The data gathered from these examinations informs conservation strategies and policy decisions. When research identifies specific threats, it provides the evidence needed to implement protective measures.
"Determining the influence of parasites on the ecology and health of marine mammals is therefore regarded as a critical step towards the implementation of appropriate management and conservation measures" 1 .
The next time you hear about a stranded dolphin or whale, remember that scientists are not merely determining a cause of death. They are reading a complex story written in tissues and organs—a story that tells us about the past, present, and potential future of life in our oceans. Through their careful work, tragedy is transformed into knowledge, and each lost life becomes a lesson in preservation for generations to come.