Remarkable Risso’s Dolphins and How to Spot Them (Responsibly)

Olivia
Jul 15
4 min read

Collectively known as cetaceans, whales, dolphins, and porpoises are some of the most well-loved and widely recognised marine creatures. They are typically large and charismatic animals, and display fascinating behaviours that have captured the minds of researchers and the public alike. From the Scottish sounds to the Celtic coastline, the UK is home to a wide variety of cetaceans, and Cornwall is no exception. A spate of migratory humpback whale sightings in early spring saw whale watchers turn their binoculars to the Cornish coast in the hope of catching a glimpse – and more recently, there has been an uptick in sightings of an equally intriguing marine mammal.

Risso’s dolphins have a distinctive appearance, quite different from the common dolphins that frequent coastlines year-round. They can measure up to 3.8m in length, with a blunt beak and stocky body. Perhaps their most distinctive feature is their significant colour variation, unique to each individual. Calves are grey, and typically darken in colour during development. They may become a lighter white-grey in adulthood, and most have prominent scarring throughout their body; in older adults, scars may become so extensive that the entire body appears white. These may be ‘rake marks’, inflicted by other dolphins, or scratches from the beaks of their cephalopod prey.

*Individual Risso's dolphins are characterised by their unique scratches and markings. Photo credit: Devon Sea Safari.*

Their behaviour is another way in which they differ from the dolphins of popular imagination. They are less agile than species such as bottlenose dolphins, and are more likely to be sighted fleetingly than to ‘bowride’ or interact with vessels. They are nevertheless sociable with one another, grouping in pods of around 10-30. Social behaviour is often physical, with tactile interaction an important form of bonding – and, as evidenced by their scars, a way of reinforcing pod hierarchy.

Why now?

Before attempting to view Risso’s dolphins, many of those living in coastal communities may ask why recent sightings have increased so dramatically. Researchers believe that the key to answering this question lies in their diet. In another unique quirk, Risso’s forgo the fish-based diet of other dolphins. Instead, they feed on octopuses, squid, and cuttlefish. It is cuttlefish in particular that may have attracted them to inshore Cornish waters.

“Most cuttlefish reproduce every year, some every other year,” says Josh Symes, who works on the Risso’s dolphin identification catalogue for Cornwall. “This means we get high cuttlefish years every other year and the Risso's are also reflected in this pattern. This year should be a high cuttlefish laying season.”

As well as the biyearly variation in cuttlefish abundance, it is believed that octopuses may be another attraction for foraging Risso’s. Symes adds, “there are huge numbers of common/Mediterranean octopus breeding around our coast at the moment. They’ve only been recently documented breeding in the UK in the last few years.” There are a number of factors that may have led to this increase, but specialists such as Devon Wildlife Trust’s Carli Cocciardi believe that warming waters due to climate change are the most likely cause.

Closer to Home

As well as how often they are sighted, the space that Risso’s dolphins occupy has also changed over time. Although they have traditionally been thought of as primarily offshore species, the range of the species has been moving closer towards our coastlines.

*Risso's dolphins appear to be moving closer towards Cornish coastlines. Photo credit: Devon Sea Safari.*

This provides a unique opportunity for land-based marine watchers - but it also means that the dolphins are more likely to be affected by human disturbance. It is therefore important that those hoping to see them do so responsibly.

Responsible Risso’s Watching

Traditionally, the best chance of seeing Risso’s dolphins has been via boat, due to their preference for offshore environments. While land watchers now have a higher chance of sightings than previously, many still prefer to use guided wildlife tours. The best way to minimise disturbance during a boat trip is to book with an operator that prioritises conservation, and is mindful of animal welfare. The ‘WiSe Scheme’ is a course offered throughout Cornwall and the UK, and WiSe accredited operators will have undergone training on minimising disturbance during wildlife watching. The SeaWatch foundation also maintains a list of recommended boat operators, who contribute to their research by collecting data during trips.

Another way to watch for Risso’s dolphins is by taking part in a land-based watch. As their range moves closer inshore, Risso’s are increasingly sighted from land. As well as being a cost-effective way to watch wildlife, this method is the least likely to cause any disturbance. It also means that you’ll be in with a great chance of witnessing natural behaviours, with little human influence. Land watches can be undertaken individually or as a group, and Falmouth Marine Conservation offers regular Seaquest events, which involve land-based surveys for marine mammals. This is a great way of getting to know fellow marine enthusiasts, as well as increasing the chances of sightings with many pairs of eyes on the water! Seaquest Sundays usually take place on the first Sunday of every month, and watchers meet at the end of Pendennis Point before the survey begins. The list of upcoming Seaquest dates is also available on the FMC website.

Land-based watches can also have a positive impact for conservation. Seaquest Southwest is a citizen science scheme encouraging members of the public to carry out surveys and report any sightings. Training is offered for those wishing to become involved as volunteer surveyors.

Despite the change in their range continuing to pose questions to scientists, Risso’s dolphins’ new proximity to human environments also offers researchers invaluable opportunities. The Risso’s dolphin identification catalogue aims to track individuals using sightings submitted by members of the public. There are over 460 dolphin profiles in the catalogue, and the project continues to grow.

*Researchers are using public sightings reports to compile a catalogue of individual dolphins. Photo credit: Devon Sea Safari*

“Any footage can be helped to match up individuals, even poorer quality,” Josh Symes explains. “That’s thanks to their unique markings that they gather through social and prey interactions.” Those who are lucky enough to encounter Risso’s dolphins in the wild are therefore encouraged to submit footage and photographs to the email address rissos@exeter.ac.uk. In this way, public interest in an increasingly prevalent species can be channelled for positive change – in Cornish waters and beyond.

For a dolphin watch checklist please download below.