Deep Connections - the social lives of sperm whales
by Chris Johnson, Global Lead, WWF Protecting Whales & Dolphins Initiative
15 February 2025
Sperm whale family along the Hellenic Trench ( July 2024). Photo taken under research permit © Chris Johnson / WWF
The morning sun reflects on the Mediterranean Sea as our research vessel, the WWF Blue Panda, cuts through the peaceful waters off Greece's northwestern islands. It's July 2024, and from the observation platform, I scan the horizon while our team listens for marine life through our specialized hydrophone trailing behind us - our acoustic window into the deep.
Below deck, our international team from Tethys Research Institute (Italy) and WWF-Greece listens intently for the distinctive voices of one of the Earth's most extraordinary marine mammals – sperm whales. Even after 25 years of studying these remarkable whales worldwide, nothing quite prepares you for the moment when you hear their voice emerge from the abyss.
Dr Simone Panigada and Viola Panigada from Tethys Research Institute on the Blue Panda. Photo taken under research permit © Chris Johnson / WWF
We're floating above the Hellenic Trench, a complex system of submarine canyons stretching over 1,300 kilometres (approximately 800 miles) from the northern Ionian Sea all the way to Rhodes in the southeastern Aegean, creating a productive critical habitat for a range of marine life. What makes this underwater canyon system truly exceptional is its dramatic deep bathymetry (seabed terrain). The trench plunges to staggering depths of over 5,000 metres (16,400 feet) in its deepest sections, creating near-vertical underwater cliffs that drop away into the darkness. These dramatic features create a natural upwelling system, forcing nutrient-rich deep waters toward the surface and generating biological hotspots where marine life flourishes. It's no wonder this area has earned recognition as an IUCN Important Marine Mammal Area (IMMA) as it’s a special hotspot for sperm whales.
Sperm whales are long-lived, deep-diving toothed whales reaching lengths of 18 metres (60 feet). They have the largest nose of the animal kingdom, specialised to use sound to communicate and navigate deep seas. The underwater landscape of the Hellenic Trench, with its dramatic walls plunging thousands of metres into darkness, provides critical habitat for sperm whales making their long, deep dives in search of their main prey - giant squid. Here, these remarkable animals, whose evolutionary journey spans millions of years, maintain complex societies that challenge our very understanding of intelligence and culture of the natural world.
Hellenic Trench sperm whale family (July 2024) © Viola Panigada / Tethys Research Institute
Suddenly, our underwater microphones come alive with a cacophony of the unmistakable rhythmic patterns of sperm whale vocalisations called “coda”. Codas, which typically consist of 3-40 echolocation ‘clicks’ arranged in distinctive, morse code-like patterns, are exchanged between whales when socialising or between long, deep, foraging dives. When we record these vocal patterns, we're witnessing the preservation of cultural knowledge in the form of this unique communication system passed down through countless generations.
Then the family group appears at the surface: a tight-knit pod of females, juveniles, and calves, their massive bodies moving with impossible grace through the clear blue sea. Sperm whale families are really special. These matriarchal family units exhibit remarkably cooperative care – while some females dive for food, others remain as "babysitters," protecting the young from predators like orcas. Their social bonds are maintained through those clicking conversations, a sophisticated communication system that coordinates their activities and preserves their cultural identity. Males typically leave their families during adolescence, joining bachelor groups or becoming solitary. Sperm whales are often called the elephants of the sea due to their similar, complex social structures.
Our research team springs into action, launching a zodiac inflatable boat and deploying specialised drones to document their behavior. Among them, we identify three newborn calves, their skin still bearing the characteristic wrinkles of recent birth, swimming in perfect synchronisation alongside their mothers. But this isn't just about energy conservation – it's the beginning of a sophisticated cultural apprenticeship that will span years.
WWF-Greece CEO Demetres Karavellas and Marine Officer Amalia Alberini searching for whales. Photo taken under research permit © Chris Johnson / WWF
What we're witnessing isn't merely a group of animals – it's a living library of cultural knowledge. Sperm whales have the largest brain on earth - nearly six times heavier than a human. Each adult female carries in her extraordinary, accumulated wisdom about foraging grounds, migration routes, and social traditions. Their clicking conversations represent one of nature's most sophisticated communication systems. These aren't just sounds; they're the threads that bind their society together as part of larger groups called ‘clans’. New research shows sperm whale clans can span ocean basins.
Sperm whales are nomads found globally. However, due to their slow recovery from 20th century whaling, they’re classified as vulnerable by the International Union for Conservation of Nature (IUCN). This Mediterranean population, however, tells a unique story. Unlike their ocean-roaming relatives, these sperm whales have adapted to live in a relatively confined sea, developing specialised feeding strategies and incredibly tight social bonds perfectly suited to the complex underwater topography of the Hellenic Trench.
Offshore oil platform in Greece © G.Paximadis / WWF-Greece
However, this idyllic scene masks a troubling reality. The sperm whale subpopulation, numbering between 200-250 individuals, is endangered and faces mounting pressures. Fast forward to January 2025, Greece announced accepting an expression of interest from oil and gas companies to conduct exploration and exploitation adjacent to the area where, in 2024, the Greek Prime Minister committed to establish a new marine park. Greece is fortunate to host unique biodiversity in the Ionian Sea and Crete, which will be directly and highly threatened, if hydrocarbon extraction platforms and other heavily polluting installations become reality. Oil and gas don’t mix with the urgency of critical marine protection.
The same waters where we documented this sperm whale family are crisscrossed by one of the busiest shipping routes in the region, with an increased risk of ship strikes. Globally, up to 30 per cent of shipping traffic is concentrated in the Mediterranean Sea. In the last 20 years, the volume of maritime traffic in this region has almost doubled and is expected to increase again in the next 15 to 20 years. In fact, over 50 per cent of whales stranded on the Greek coasts show marks of boat collisions, making vessel strikes an urgent threat for this population today.
Each passing ship also adds to the underwater noise that masks sperm whales’ biosonar, crucial for communicating, navigating, and feeding. Entanglements in fishing gear, ingestion of plastic pollution, overfishing, and climate change impacts are putting additional pressures on their survival.
Sperm whale family along the Hellenic Trench with Blue Panda and a zodiac inflatable boat in the background (July 2024). Photo taken under research permit © Chris Johnson / WWF
Yet there is hope. Each encounter we document improves our understanding of the sophisticated social lives these animals lead and adds weight to our case for their protection.
Memories from that summer day will be everlasting. As the day ended, their clicks continued throughout the night and faded into the deep. We were reminded that protecting sperm whales means preserving more than just a species – it means safeguarding an ancient cultural heritage that enriches our ocean. Their future depends on the choices we make today to protect their deep-water canyons and ensure safe passage through their marine blue corridors. In doing so, we preserve both generations of families and ocean wisdom that has endured for millennia.
