Grampus griseus (Risso’s Dolphin)
Risso’s dolphin
A remarkable marine mammal known for its distinct appearance and social behaviours. Found in temperate and tropical oceans worldwide, including waters around the UK, these dolphins captivate both marine enthusiasts and researchers alike.
Physical Characteristics
Risso’s dolphins are medium-sized, reaching up to 4 meters in length and weighing between 300 and 500 kilograms. They are easily recognized by their bulbous head, blunt snout, and a body covered with white scars, which are thought to result from social interactions and encounters with prey. Their coloration ranges from dark grey to almost white in older individuals.
Habitat and Distribution
These dolphins prefer deep offshore waters and are often found along continental slopes. In the UK, sightings are most common in the waters off Scotland, Wales, and southwestern England. They are especially associated with areas where squid, their primary food source, are abundant.
Diet and Feeding
Risso’s dolphins primarily feed on squid but also consume other cephalopods and occasionally small fish. They use echolocation to detect and capture their prey in deep waters, often diving to impressive depths.
Social Behaviour
Risso’s dolphins are highly social and usually travel in groups, or pods, of 10–30 individuals. These pods can consist of different age groups and sometimes include other dolphin species. They communicate through clicks, whistles, and body language, showcasing their intelligence and complex social structures.
Reproduction and Lifespan
Females give birth to a single calf after a gestation period of around 13–14 months. The calf is nursed for at least a year and remains with its mother for an extended period. Risso’s dolphins are thought to live for more than 30 years, with some individuals reaching their 40s.
Ecological Role
As predators of squid and other cephalopods, Risso’s dolphins play a vital role in regulating these populations in marine ecosystems. Their feeding habits also contribute to nutrient cycling in the ocean.
Threats and Conservation
Risso’s dolphins face several threats, including bycatch in fishing gear, pollution, and habitat disturbance from marine traffic and underwater noise. Climate change also impacts their prey availability. Despite these challenges, they are protected under various international agreements, including the EU Habitats Directive and the UK’s Wildlife and Countryside Act.
Cultural Significance
These dolphins have long been a source of fascination and inspiration in coastal communities. Their scars and unique behaviors often symbolize resilience and adaptability in the face of nature’s challenges.
Conservation Efforts
Efforts to protect Risso’s dolphins include establishing marine protected areas, promoting sustainable fishing practices, and reducing underwater noise pollution. Continued research and public education are crucial for their conservation.
Conclusion
Risso’s dolphins are an integral part of marine ecosystems and a testament to the ocean’s diversity. Protecting these fascinating creatures ensures the health and vitality of our seas for future generations.