Risso’s Dolphin

A Body Etched by Experience

Risso’s Dolphins are medium-sized cetaceans that typically grow between 8.5 and 13 feet long and can weigh up to 1,100 pounds. One of their most striking features is the blunt, rounded forehead, known as a melon, which lacks the distinct beak that characterizes many other dolphins. Their dorsal fin is tall, curved, and almost sail-like, giving them a dramatic silhouette against the ocean waves.

But it’s their skin that tells the most compelling story. Risso’s Dolphins are born a dark gray or brown color and grow lighter with age. Over time, their bodies accumulate numerous scars, mostly from interactions with other dolphins or from the tentacles of squid, their primary prey. Older individuals are often so heavily scarred that their skin appears almost white, creating a ghost-like appearance that adds to their mystique.

Deep Divers and Night Hunters

Risso’s Dolphins have a strong preference for deep waters, especially along continental shelves and underwater canyons. These habitats provide access to their favorite food source—squid. While they will occasionally eat fish or crustaceans, their diet revolves around various squid species that live in the mesopelagic or “twilight” zone of the ocean, hundreds of feet below the surface.

To catch these elusive creatures, Risso’s Dolphins dive deep and often at night when squid migrate upward. Using echolocation, they navigate the dark waters and locate prey with remarkable precision. Their beakless mouths are filled with peg-like teeth in the lower jaw, which help grip slippery squid. Hunting often occurs in groups, suggesting that social cooperation is as much a part of their feeding strategy as individual skill.

Traveling in Good Company

Social life is central to Risso’s Dolphins. They are commonly found in pods of 10 to 30 individuals, though in rich feeding areas or during migrations, superpods of hundreds have been recorded. These groups often exhibit tight cohesion, swimming in parallel or synchronously surfacing, suggesting a strong social bond among members.

Unlike some dolphin species that exhibit complex hierarchies, Risso’s Dolphins appear to operate with more flexible group dynamics. Pods may consist of all males, all females with calves, or mixed groups, and individuals may switch between pods over time. Despite their preference for the deep sea, they sometimes come close to shore, especially in areas with steep underwater drop-offs, offering lucky observers a rare chance to witness their social behaviors firsthand.

From Birth to Bond: Raising the Next Generation

Reproduction among Risso’s Dolphins typically follows seasonal patterns, with births occurring in warmer months depending on geographic location. Mating behaviors are not well-documented, but like many dolphins, they likely involve displays of physical agility and close social interactions. Males may compete for access to females through body postures, vocalizations, or bursts of speed.

The gestation period lasts about 13 to 14 months, after which a single calf is born tail-first. The newborn measures around 4.5 to 5 feet and is nurtured closely by its mother. Nursing can continue for over a year, but calves often remain with their mothers for extended periods, learning how to hunt, navigate, and interact with others. Female dolphins may form nursery groups, where multiple mothers help watch over the young, fostering a supportive environment for their development.

Quiet Communicators of the Sea

Risso’s Dolphins are vocal, though their sounds are less studied than those of their more famous cousins. They use a variety of clicks, whistles, and burst pulses to communicate and echolocate. These vocalizations help them stay connected within pods, coordinate during hunts, and navigate through dark or murky waters. Because they often reside in deeper waters, recording and analyzing their vocal behavior presents logistical challenges for researchers.

Their communication also includes body language. Tail slaps, leaping, and synchronized swimming are all thought to play roles in social signaling. Though generally considered less acrobatic than species like the Spinner Dolphin, Risso’s Dolphins do breach and spy-hop on occasion. These behaviors may serve multiple purposes, from removing parasites to establishing dominance or simply expressing excitement.

Citizens of a Global Ocean

Risso’s Dolphins have one of the widest distributions of any dolphin species. They are found in temperate and tropical waters around the world, including the Atlantic, Pacific, and Indian Oceans. They favor deep offshore waters but can sometimes be seen along steep continental slopes or near oceanic islands where the seafloor drops off quickly.

In regions like California, the Azores, and parts of Japan, they are regular seasonal visitors. Their movements often follow the migrations of squid and other prey, although detailed migration patterns remain poorly understood. Unlike some dolphin species with highly localized populations, Risso’s Dolphins show remarkable flexibility, allowing them to adapt to various oceanic conditions.

The Battle Scars of Living Wild

The extensive scarring on Risso’s Dolphins is not just a defining visual trait—it is also a glimpse into their rugged lives. Most of the scars are thought to come from squid, whose sharp tentacle hooks can leave permanent marks during a struggle. Others are likely the result of social interactions, as dolphins may rake one another with their teeth during disputes or playful tussles.

These marks are so prominent and individualized that researchers can often identify individuals based on their scar patterns. This natural form of photo-identification has become a useful tool in long-term population monitoring. In some cases, the amount and type of scarring can also provide clues about the dolphin’s age, sex, and social history, making their skin an open record of their experiences.

A Touch of Culture: Interactions with Other Species

Risso’s Dolphins don’t live in isolation. In some parts of the world, they are known to interact with other marine species, including different types of dolphins and even whales. Mixed-species pods have been observed, particularly with Bottlenose Dolphins or Pilot Whales, sometimes resulting in cooperative foraging or temporary alliances.

These interactions may provide social stimulation or access to food sources, but they can also lead to competition. On rare occasions, aggressive encounters have been recorded, though the purpose behind them remains speculative. These mixed-group behaviors add another layer of depth to the already complex lives of Risso’s Dolphins, hinting at a subtle social intelligence that extends beyond their own kind.

A Quiet Presence in the Spotlight

While they are not as well-known as other dolphins, Risso’s Dolphins are slowly gaining recognition through ecotourism and marine research. Whale-watching tours in places like the Azores, Scotland, and Monterey Bay often include sightings of these unique animals. Their ghostly appearance and quiet elegance captivate those lucky enough to see them in the wild.

This growing visibility has helped generate more public interest and scientific funding for studying their behavior, vocalizations, and habitats. Because they are elusive and prefer offshore areas, each new observation contributes valuable data. Slowly, a fuller picture of Risso’s Dolphin life is emerging, piece by piece, from the depths of the ocean.

Navigating Modern Threats

Like many marine species, Risso’s Dolphins face an array of human-induced challenges. The most significant among these are entanglement in fishing gear and the impacts of naval sonar and other underwater noise pollution. Gillnets and longlines used in deep-sea fishing can accidentally trap dolphins, causing injury or death. Because Risso’s Dolphins tend to swim in mid-depth and deep waters, they are particularly at risk from these fishing practices.

Noise pollution is another concern. Loud underwater sounds from naval exercises, seismic surveys, and ship engines can disrupt the dolphin’s echolocation, disorienting them or forcing them to abandon critical habitat. In some cases, these disturbances have been linked to strandings. Pollution, including microplastics and chemical contaminants, also poses long-term risks to their health and reproductive success.

Protecting a Lesser-Known Cetacean

Conservation efforts for Risso’s Dolphins are underway but often fall under broader protections aimed at marine mammals in general. They are listed on Appendix II of the Convention on Migratory Species and are protected in many countries under national marine legislation. In some areas, marine protected zones overlap with their known habitats, providing some measure of safety from industrial impacts.

Public education and responsible ecotourism can also play a part in their conservation. When people are introduced to these remarkable animals through ethical wildlife experiences, they’re more likely to support protective measures. Continued scientific research is vital to better understand their needs, population trends, and threats, enabling smarter conservation strategies moving forward.

An Ancient Connection: Risso’s Dolphins in Human Culture

While not as prominent in folklore as other dolphins, Risso’s Dolphins have long intrigued seafarers. Their pale, scarred appearance and tall dorsal fins have sparked legends of sea monsters or ghostly ocean spirits. In some cultures, dolphins were seen as omens or protectors of sailors, and Risso’s unique look may have added to these myths.

In modern times, their increasing visibility through photography, documentaries, and ecotourism has helped reshape their image. They are now celebrated not for their flashiness, but for their quiet strength and unusual beauty. In a world that often values the loudest or most showy creatures, Risso’s Dolphins remind us that there is great power in mystery and subtlety.

A Life of Rhythm and Ritual

Risso’s Dolphins follow a daily rhythm that centers around diving, foraging, and resting. They often feed at night, when squid rise closer to the surface. During the day, they may rest near the surface, drifting slowly or swimming in tight formation with their pod. This quiet period is vital for recovery and social bonding.

Their diving behavior is impressive. Risso’s Dolphins can hold their breath for more than 30 minutes and dive to depths exceeding 1,000 feet. These deep excursions are physically demanding and require efficient oxygen use, high myoglobin concentrations in muscles, and precise navigation skills. Over time, this daily routine builds a strong physical and social structure, allowing them to thrive in a challenging marine world.

Final Thoughts: The Grace of the Unknown

Risso’s Dolphins are not the most famous or flashy marine mammals, but they possess a rare kind of magic. Their pale, scarred bodies glide silently through deep waters, hinting at stories written in tooth marks and tentacle scratches. They live in tight social groups, communicate through layered sounds, and raise their young in offshore worlds we are only beginning to understand.

They are symbols of resilience and reminders of the ocean’s vast, still-hidden complexity. Every encounter with a Risso’s Dolphin offers a moment to appreciate the quiet strength of a life well-adapted to a wild and fluid world. As science uncovers more about them, one truth remains clear—Risso’s Dolphins deserve a place in our imagination, our research, and our commitment to protect the oceans they call home.