Humpback whales often carry a diverse community of organisms on their bodies. This phenomenon is a natural aspect of their lives, showcasing unique relationships between different marine species. These organisms find a mobile habitat on the whale’s vast surface.
The Main Organisms
Humpback whales commonly host several types of organisms, primarily barnacles, whale lice, and diatoms. Among the barnacles, Coronula diadema is frequently observed. This species, often called the “whale barnacle,” can reach sizes of up to 5 cm in height and 6 cm in diameter, resembling a crown or barrel with six broad wall plates. Another barnacle, Conchoderma auritum, often attaches to Coronula diadema shells.
Whale lice, belonging to the genus Cyamus, are small crustaceans, not true insects. These flattened creatures range from a few millimeters to about 2.5 centimeters in length, with claw-like legs designed for clinging to the whale’s skin. Their coloration, reddish-orange or pale, helps them blend with their host’s skin. Over 30 species of whale lice have been identified. Diatoms, microscopic algae, can also form yellowish patches on the bellies of some whales.
Reasons for Attachment
These organisms attach to humpback whales primarily for mobility, access to food, and protection. Barnacles, being sessile in their adult stage, rely on the whale for transportation to nutrient-rich waters. As filter feeders, they extend feathery appendages called cirri into the water to capture plankton and detritus as the whale swims. The whale’s movement ensures a constant supply of food, making it an efficient feeding platform. Barnacle larvae are chemically cued by whale skin to settle and attach, secreting a strong cement-like substance to anchor themselves.
Whale lice also benefit significantly from their association with humpbacks. They cling to areas on the whale’s body that offer protection from strong water currents, such as around natural body openings, wounds, and skin folds. These areas include the head, flippers, and ventral pleats for baleen whales. Whale lice primarily feed on flaking skin, dead tissue, and algae that accumulate on the whale’s body. Their inability to swim or survive in open water makes the whale a necessary and permanent habitat.
The Relationship with Humpbacks
The relationship between humpback whales and these attached organisms is considered commensal, meaning one organism benefits while the other is largely unaffected. While barnacles and whale lice do not cause significant harm, a large accumulation of barnacles can increase drag, requiring the whale to expend more energy for swimming. A single humpback whale can carry hundreds of kilograms of barnacles.
Humpback whales employ various behaviors to manage their external passengers. Breaching, where the whale leaps out of the water and crashes back down, can help dislodge some barnacles and dead skin. Whales also rub against the seafloor, rocks, or even other whales to scrape off barnacles and whale lice. This “exfoliation” behavior helps maintain healthy skin and removes ectoparasites. While these actions can reduce the load, larger, deeply embedded barnacles are difficult for whales to remove entirely on their own.