What are barnacles on whales

Barnacles and whales share one of the ocean’s most familiar commensal relationships. These crustaceans attach to whale skin using a powerful cement-like substance and ride along for the whale’s entire migration, feeding on plankton swept past them as the whale moves through the water.

How Barnacles Attach to Whales

Barnacles are crustaceans that attach to hard surfaces as larvae, then grow a calcified shell around themselves. On whales, they use a biological cement that is one of the strongest natural adhesives known, bonding directly to the whale’s skin. The larvae settle in areas with lower water flow, such as the chin, flippers, and tail of whale behavior.

The attachment process begins when free-swimming barnacle larvae (cyprids) encounter a whale and select a suitable location. Once settled, the barnacle undergoes metamorphosis, developing its characteristic shell and beginning to filter-feed. Some barnacle species have evolved to live exclusively on certain whale species, demonstrating a long evolutionary association.

Effects on Whales

The relationship between barnacles and whales is generally classified as commensal, meaning the barnacles benefit while the whale is neither significantly harmed nor helped. However, heavy barnacle loads can increase hydrodynamic drag, potentially costing the whale extra energy during whale conservation.

A single gray whale can carry over 400 pounds of barnacles, primarily the species Cryptolepas rhachianecti. Some researchers have suggested that barnacle clusters on humpback whale flippers may actually serve a defensive purpose, as the rough, sharp shells could cause injury to attacking predators. Learn more about whale defense mechanisms in our guide on whale diet.

Species That Carry Barnacles

Not all whale species carry equal barnacle loads. Gray whales are the most heavily colonized, often appearing almost white from barnacle coverage. Humpback whales carry significant loads on their flippers and chin (the bumps called tubercles often host barnacles). Right whales develop distinctive callosities where barnacles and whale lice accumulate. In contrast, faster-swimming species like blue whales and killer whales tend to carry fewer barnacles due to their speed and smooth skin.

Barnacles as Research Tools

Scientists have discovered that barnacle shells record chemical information about the water they grow in, similar to tree rings. By analyzing the isotopic composition of barnacle shells, researchers can reconstruct whale migration routes and feeding histories. This technique has provided valuable data for whale sounds efforts.

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