Skin Diseases and Physical Deformities in Dolphins
& Implications for Human Health

Why is this project important?

Our past studies show that bottlenose dolphins off Southern California suffer skin lesions and physical deformities. Ours was the first investigation of this kind on the West Coast of the United States. The presence of these lesions – which may indicate epidermal diseases – is related to environmental factors like sea temperature and salinity, but also man-made pollutants in our waters. This is of concern because it has potential implications for human health.

What has our research team already learned?

Limitations of Other Studies

Investigations of dermal skin lesions and physical deformities in wild bottlenose dolphins prior to our investigation have been generally scarce and the majority of studies have been focused on dead or captive animals.

OCS Research Insights

From 1997-2007, the OCS research team cataloged and analyzed a variety of dermal lesions and physical deformities on free-ranging bottlenose dolphins off Southern California (read our publication on skin lesions). This raised concerns about the health status of this species and potential negative effects on the entire coastal and offshore dolphin populations.


percentage of bottlenose dolphins in our study area showing skin diseases and/or body malformations

What are our current project goals?

The cause of many dermal lesions is still unknown, but an increasing number of studies on wild bottlenose dolphins suggest that both lesions and deformities are anthropogenically induced (caused by humans).

Our current research aims to continue the monitoring of this population both along the coast and in offshore waters to shed more light on the occurrence, extent and frequency of these lesions and malformations.

We also plan to compare our data with other studies conducted off California. This will help to assess changes in skin lesion presence and extent over time, at both the population and individual levels.

How do we collect data on skin lesions & body malformations?

For this project, we photograph not only dolphin dorsal fins (via a process known as photo-ID), but we also take pictures of the upper body of individuals in each group encountered during a survey. These images are an excellent tool to assess the presence and prevalence of epidermal lesions because of their visibility.

Skin lesion images are then grouped into different categories based on color, shape, extent, etc. Physical deformities are classified as conformational deformities (humpbacked, bent dorsal fins, lumps) and as different types of spinal malformations. 

“How our skin appears often reflects how
we feel, and the same is true of dolphins.”

Dr. Maddalena Bearzi

OCS President and Research Director since 1996

How is this project important for conservation?

Fungal, viral, and bacterial infections, as well as a reaction to parasites, have been identified among the main causes of skin lesions and physical deformities in dolphins. Studies show that both infectious and noninfectious diseases are likely to have harmful impacts on population abundance and reproduction, even causing the death of individuals.

Bottlenose dolphins are exposed to a high accumulation of marine pollutants because of their position at the top of the food chain. When a pollutant enters the ocean, it’s carried up the food web, increasing in toxicity with every trophic level, a process known as biomagnification.

This “build-up” of toxins leads to a bio-accumulation of contaminants in the bodies of marine mammals. That’s why dolphins are so vulnerable to indirect threats such as chemical pollution. This is dangerous for humans too, considering we also rely on fish as a food source!

The coastal bottlenose dolphin population is particularly susceptible because it inhabits near-shore regions where pollution is usually abundant. Some contaminants have already been associated with many skin lesions in bottlenose dolphins. Our study area off Los Angeles – where a high percentage of skin lesions has been found on bottlenose – has shown significantly higher concentrations of contaminants relative to other regions off California.

Due to their long-life span and position in the food chain, bottlenose dolphins are important sentinel species not only for the ecosystem but also for public health, so monitoring their status is key for conservation.


We urgently need help to learn more about diseases affecting these animals

When we pollute the oceans, we can see signs of our negative impacts – even on the skin of dolphins! If dolphins get sick, we can get sick too (we eat the same fish!) Knowing more about diseases in these animals is key to helping them – and ultimately also protecting us. Your valuable financial support will go directly toward our on-the-water research and lab studies to address this problem.


Learn about our other research projects