Barnacles, marine crustaceans related to crabs and lobsters, commonly associate with whales. These sessile organisms attach to various surfaces in the ocean, including the skin of large marine animals. This relationship has existed for millions of years, representing a long-standing interaction in marine ecosystems.
How Barnacles Attach to Whales
Barnacles begin their lives as tiny, free-swimming larvae, progressing through a cyprid larval stage that finds a suitable host to settle on permanently. These larvae can sense chemical cues released from the whale’s skin, which helps them identify a host. Once a cyprid larva encounters a whale, it attaches itself to the skin, often in areas where water flow is consistent and less turbulent, such as the head, fins, or tail flukes. The barnacle then secretes a strong, cement-like adhesive, and as it grows, its shell plates embed into the whale’s epidermis, creating a secure connection.
Direct Impacts on Whale Health
The presence of barnacles can lead to several direct consequences for whale health. A primary physical effect is the increased hydrodynamic drag caused by the barnacles, which requires the whale to expend more energy for swimming. This added resistance can be significant, particularly for whales carrying hundreds of pounds of barnacles. Barnacle attachment can also cause irritation and inflammation on the whale’s skin, and in some instances, may lead to open wounds or lesions.
Broader Ecological and Behavioral Effects
The direct impacts of barnacles can extend to broader ecological and behavioral consequences for whales, as increased drag from barnacle infestations can significantly raise the energy cost for long-distance migrations and foraging activities. This increased energy demand can affect a whale’s overall fitness and reproductive success. Barnacles also influence a whale’s behavior, leading to altered swimming patterns or increased rubbing against surfaces. Whales might also engage in behaviors like breaching or slapping the water, which may help dislodge barnacles, while chronic irritation and the continuous energy demands impact a whale’s growth rates and overall ability to thrive.
How Whales Cope
Whales employ various natural strategies to manage barnacle infestations, though complete removal of firmly attached barnacles can be challenging. Some whale species, like gray whales, periodically shed their outer layer of skin, a process known as epidermal molting, which helps remove accumulated barnacles and other ectoparasites. Whales also engage in specific behaviors to dislodge barnacles; for example, humpback whales have been observed rolling on sandy seabeds, effectively using the sand to exfoliate their skin and remove barnacles. Breaching, where whales leap out of the water and crash back down, is another behavior that may help dislodge barnacles. Despite these efforts, whales have evolved a degree of tolerance to the presence of barnacles, and for most healthy individuals, barnacles are generally considered a nuisance rather than a severe threat.