Barnacles are marine crustaceans, distantly related to crabs and lobsters, commonly observed clinging to various surfaces in the ocean. Whales are large marine mammals inhabiting all the world’s oceans. Barnacles are frequently seen attached to whale skin. This association prompts questions about its nature and consequences.
The Whale-Barnacle Relationship
Barnacles typically begin as microscopic, free-floating larvae in the ocean. When these larvae encounter a whale, they adhere to its skin using a specialized, strong cement-like substance. As the barnacle matures, it forms a hard shell and creates tube-shaped cavities that embed into the whale’s skin. This firm attachment allows sessile barnacles to gain a stable habitat and a constant flow of nutrient-rich water as the whale moves through the ocean. This arrangement is often considered a commensal relationship, where the barnacle benefits from a mobile home and access to food, while the whale is largely unaffected.
Adverse Effects on Whales
While often described as commensal, the relationship between barnacles and whales can become detrimental, particularly with heavy infestations. One significant impact is the increased hydrodynamic drag caused by their presence on the whale’s body. This added resistance requires the whale to expend more energy for swimming, affecting its overall efficiency. This increase in drag directly correlates with higher metabolic costs.
The attachment of barnacles can also lead to skin irritation and lesions on the whale’s body. The barnacles’ deep embedding or large clusters can cause discomfort and open wounds. Such skin damage can create entry points for secondary infections, impacting the whale’s health. For filter-feeding whales, extensive barnacle growth around sensitive areas like the mouth or baleen plates could interfere with efficient feeding.
A large accumulation of barnacles adds extra weight to the whale, with some humpback whales reportedly carrying up to 1,000 pounds (450 kg) of barnacles. While this mass is relatively small compared to a whale’s total body weight, it contributes to the overall burden. This additional weight, combined with increased drag, can affect the whale’s buoyancy and swimming dynamics.
Factors Influencing Impact Severity
The severity of barnacle impacts on whales is not uniform and depends on several factors. Different barnacle species have varying sizes and attachment mechanisms. The whale species and its typical behavior also play a role, as slower-moving baleen whales tend to accumulate more barnacles than faster-swimming toothed whales. Whales undertaking long migrations may also accumulate more barnacles over time.
The specific location of barnacle attachment significantly influences the impact. Barnacles situated on critical areas such as around the blowholes, eyes, or extensively on the fins or feeding apparatus, can exert a greater negative effect. Barnacles often prefer areas with consistent water flow, like the head and pectoral fins, for optimal filter feeding. The number and density of barnacles on an individual whale also directly correlate with the severity of the effects.