The deep-sea Risso's dolphins are having a moment. Or, rather, they're having multiple moments, as they're spending more time inshore than usual due to the influx of octopuses in the waters around south-west England. This phenomenon is keeping these cephalopod-loving marine mammals in local waters longer than expected, and it's got researchers buzzing with excitement. But what does this mean for the dolphins, and what does it tell us about the ocean's changing dynamics?
A cephalopod feast
Marine biologist Josh Symes, who runs the Risso's Dolphin Photo ID project for Exeter University, is witnessing a unique situation. The number of octopus sightings has surged, and with it, the presence of Risso's dolphins in the area. This is no coincidence, as these dolphins primarily feed on cephalopods, including squid, octopus, and cuttlefish. The abundance of these prey species is providing an ample food source, encouraging the dolphins to linger in the shallower waters.
Symes explains, "There's been an octopus bloom last year, and cuttlefish are also increasing. They're coming inshore to feed on inshore spawning cuttlefish and then obviously now there's lots of octopus around, it gives them even more reason to kind of stick around."
Citizen science in action
The Risso's Dolphin Photo ID project is a brilliant example of citizen science. By engaging the public to report sightings, the project has been able to track the dolphins' movements and behaviors. In 2025, the number of reported sightings more than doubled compared to previous years, indicating a growing awareness and interest in these marine mammals. Symes attributes this to both increased public engagement and the abundance of food sources.
Risso's vs. Orca
One fascinating aspect of Risso's dolphins is their size and behavior. Symes notes, "I find Risso's really intriguing because for such a big dolphin, they can be really, really clever and discreet. Sometimes they get misreported for Orca because they are so big, bigger than most of the dolphins we get around here."
This highlights the importance of accurate identification, as Risso's dolphins can be easily mistaken for the more famous Orca (killer whale).
A changing ocean
The story of Risso's dolphins and their octopus feast is a fascinating glimpse into the complex web of marine life interactions. It raises questions about the impact of climate change and ocean warming on these delicate ecosystems. As warmer temperatures contribute to the proliferation of octopuses, we may see more of these dolphin-octopus interactions in the future.
In my opinion, this research underscores the importance of understanding the interconnectedness of marine species. It also serves as a reminder that human activities, such as climate change, can have far-reaching consequences on the delicate balance of our oceans. As we continue to explore and study these environments, we must remain vigilant and proactive in our efforts to protect and preserve them.
