Blue whales, the largest animals ever to exist on Earth, produce some of the loudest sounds in the animal kingdom. These colossal marine mammals navigate and communicate in the vast ocean depths, relying on a complex acoustic world largely hidden from human perception. Their powerful vocalizations hold secrets about their lives, from movements across oceans to social interactions. Understanding these sounds provides insights into these magnificent creatures.
The Sounds of Blue Whales
Blue whales produce very low frequency, or infrasonic, vocalizations, meaning they fall below 20 Hz, the range of human hearing. These deep, resonant sounds can travel immense distances through the ocean, hundreds or even thousands of kilometers. Their calls are among the loudest animal sounds on Earth, reaching intensities of up to 180 decibels, comparable to a jet plane.
Blue whale vocalizations are long, patterned songs consisting of moans, groans, and pulses. One common type of call is the “B-call,” a 9-second, 27-Hz tone, sometimes followed by downsweeps to lower frequencies around 18-19 Hz. These calls are often repeated at regular intervals, increasing their detectability.
Why Blue Whales Vocalize
Blue whale vocalizations serve several purposes, primarily for communication over vast distances. These low-frequency sounds allow individuals to maintain contact across wide oceanic expanses, useful for finding mates or coordinating movements. Male blue whales, for instance, are known to produce more calls, suggesting a role in reproduction.
These sounds also aid in navigation and foraging. Blue whales may use vocalizations to map their environment, listening to echoes bouncing off distant underwater features like seamounts or coastlines. This helps them navigate and locate areas rich in prey. Research suggests whales also call to signal the presence of food, inviting others to join in cooperative foraging.
Listening to Blue Whales
Scientists employ passive acoustic monitoring to study blue whale sounds. This method involves deploying hydrophones, specialized underwater microphones, to record ocean sounds. These devices can be moored to the seafloor for continuous listening or towed behind research vessels.
Hydrophone arrays, multiple hydrophones at different locations, allow researchers to pinpoint the exact position of a vocalizing whale by analyzing slight differences in sound arrival times. The data provides insights into whale movements, population distribution, and behavioral patterns. This non-invasive approach is useful for studying endangered species like blue whales, offering information for their conservation.
Human Activity and Whale Sounds
Human-generated noise in the ocean impacts blue whale communication and survival. Sources such as commercial shipping, seismic surveys, and naval sonar introduce loud sounds that interfere with the whales’ acoustic environment. This interference is “acoustic masking,” where human noise drowns out whale vocalizations, making it difficult for them to hear each other.
The overlap in frequencies between human noise and whale calls can disrupt their ability to communicate for foraging, mating, and navigation. For example, blue whales may reduce their calling activity in the presence of mid-frequency active sonar, especially when the sonar source is closer and louder. This noise pollution can lead to changes in behavior, increased stress, and affect their overall health and reproductive success.