Do barnacles hurt whales?

The Relationship Between Barnacles and Whales

Barnacles and whales share one of the ocean’s most visible symbiotic relationships. Whale barnacles (Coronula diadema and related species) are specialized crustaceans that attach themselves to the skin of various whale species, particularly humpback whales and gray whales. The question of whether these hitchhikers cause harm is more nuanced than a simple yes or no.

Mostly Harmless: Commensalism

Scientists classify the barnacle-whale relationship as primarily commensal, meaning one organism benefits while the other is neither helped nor harmed:

• Barnacles benefit: They gain a mobile platform that carries them through nutrient-rich waters, providing a constant flow of plankton and other food particles
• Whales are mostly unaffected: The weight and drag of barnacles is negligible compared to the whale’s massive body

Potential Negative Effects

While barnacles are not considered parasites, heavy infestations may cause minor issues:

• Increased drag: Large accumulations of barnacles increase water resistance, potentially requiring the whale to expend slightly more energy while swimming. A single humpback whale can carry up to 1,000 pounds (450 kg) of barnacles.
• Skin irritation: The cement-like adhesive barnacles use to attach can cause localized skin damage or irritation at the attachment site
• Secondary infections: Damaged skin around barnacle attachment points could theoretically become vulnerable to infections

However, these effects are considered minor relative to the whale’s overall health. Healthy whales appear to tolerate barnacle loads without significant distress.

Potential Benefits to Whales

Some researchers have suggested barnacles might actually benefit whales in certain ways:

• Defensive armor: The rough, barnacle-encrusted skin of humpback whales may serve as a form of protection. During aggressive encounters, a barnacle-covered flipper or tail can inflict more damage on rivals or predators.
• Camouflage: On gray whales, the mottled pattern created by barnacles and whale lice may provide some visual disruption, potentially making them harder for orca predators to target.

Which Whales Get Barnacles?

Not all whale species carry barnacles equally:

Species	Barnacle Load	Common Species
Humpback whale	Heavy	Coronula diadema, Coronula reginae
Gray whale	Very heavy	Cryptolepas rhachianecti
Right whale	Moderate	Tubicinella major
Blue whale	Light	Occasional Coronula
Sperm whale	Minimal	Rarely colonized

Fast-swimming species like blue whales and fin whales tend to carry fewer barnacles, possibly because their speed makes attachment more difficult.

How Barnacles Attach

Whale barnacles have evolved specialized adaptations for life on whale skin. They secrete an extremely strong biological cement that bonds directly to the whale’s outer skin layer. Unlike ship-fouling barnacles, whale barnacles do not bore into flesh — they sit on the surface. Some barnacles are embedded in shallow depressions in the whale’s skin, which may form naturally as the skin grows around the barnacle base.