Rome, the Eternal City, is known for its rich history, art, culture, and cuisine. However, a lesser-known fact is that just an hour away from the city, where the Tiber River flows into the Tyrrhenian Sea, lies a unique area inhabited by a population of around 500 bottlenose dolphins. These dolphins, known as the "Capitoline dolphins," have been a part of the coast outside Rome for thousands of years, as evidenced by mosaics from the archaeological site of Ostia Antica that depict them stealing fish from fishermen's nets 2,000 years ago.
Despite their long history in the region, these dolphins have only recently been closely studied, beginning in 2016. A recent study conducted by researchers at the Sapienza University of Rome has revealed a worrying picture of their health and well-being. The analysis of more than 400 photographs taken between 2016 and 2023, depicting 39 individuals of the resident population, showed that 70 percent of the dolphins studied showed signs of malnutrition, such as visible ribs. This is unusual given the richness of food in the area.
The researchers believe that the lack of food might be due to overfishing, which has led to dwindling food resources for the dolphins. Furthermore, half of the dolphins' bodies had marks from the lines and ropes used by fishermen, and amputations were present as well. Nearly all, or 97 percent, of the dolphins had a skin disease caused by pollution from the Tiber River and wastewater from boats passing through. "Pollution can promote immunodepression and cause animals to get sick," says Alice Turchi, a PhD student in environmental and evolutionary biology at the Sapienza University of Rome and author of the study.
In addition to these health issues, researchers also found evidence of fighting among the dolphins. They analyzed teeth marks caused by interactions with other dolphins, which were universal across the population. While these marks are sometimes normal for dolphins as they can bite to communicate dominance during mating competitions or to establish social hierarchies, this population showed an unusually high number. The researchers believe that this may be due to competition for dwindling food resources.
The findings on the Capitoline dolphins' health are consistent with what we observe in many coastal bottlenose dolphin populations worldwide. These populations are exposed to continuous and intense pressure from human activities, ranging from fisheries and maritime traffic to pollution and habitat degradation. For example, in Galicia on the Atlantic coast of Spain, we see similar patterns of skin marks related to both natural and anthropogenic factors. Similarly, studies from other regions such as Sarasota Bay in the United States or various sites in Australia also report high frequencies of marks linked to social interactions.
The Capitoline dolphins' story is a reminder of the need for conservation efforts to protect these vulnerable marine mammals from the impacts of human activities. As we continue to explore and develop our surroundings, it is crucial to remember that we share this planet with many other living beings who depend on it for their survival.
