Acoustic Functions of the Sounds

Produced by the Spermaceti Organ

Photo taken by Leslie Smith off Abaco Island, Bahamas. There are three different whales in this photo logging after a dive.Two of which we thought were adult females and one that we thought to be a calf belonging to one of the females.

Hearing Ability

Because sound travels farther in water than light, it becomes advantageous for marine mammals to rely more on auditory cues than visual cues in order to communicate effectively under water. Sperm Whales have excellent hearing capabilities because their soft tissues have similar acoustic properties as the water that they live in (Cranford 1999). Their ears are especially sensitive to high frequency and short duration signals (Cranford 1999). As a result, they can hear minute sounds from very far away. It is hypothesized that the evolution of echolocation may have been an important factor in the radiation of odontocetes.

Hunting

Echolocation, facilitated by the clicks produced in the spermaceti organ, is used in hunting by sperm whales to effectively locate their prey (Morris 1973). These sounds can also be used to debiliate prey when produced loud enough to help facilitate their capture (Cranford 1999)

 

Sexual Selection

Sounds are also used in acoustic courtship displays (Cranford 1999). Large males can advertise themselves to females, and other competing males by the sounds they make. The length and slightly curved shape of the spermaceti organ, together with the geometry between the acoustically reflective air interfaces determines the impulse interval (Cranford 1999). In other words, the bigger the nose, the longer the impulse interval. Larger noses are high investments and very costly to the individual because the fat stores located there are isolated from the rest of the body and cannot be accessed, even in times of crisis (Cranford 1999). As such, a sperm whale could starve, and the dead body would be found still with the spermaceti organ full of oil (Cranford 1999). This provides a high investment, clear cut way for females to select mates with high fitness, and is a trait that is near impossible to fake. Sound is also an efficient way for reproductive dislays underwater because they can be effective over large ranges at any depth day or night (Cranford 1999).

Photo taken by Leslie Smith off Abaco Island, Bahamas. This whale is shown tail slapping . This female sperm whale was probably calling her calf because shortly after the tail slapping episode, a smaller whale surfaced next to her.

 

Social

Sounds can also be produced for communication between sperm whales. Acoustic sounds can be used for a variety of different social situations. It can be used for communication between members of the same pod during dives (Cranford 1999). It can also facilitate social interactions of establishing acoustic territories, particularly for male sperm whales, and is also used for threat displays (Cranford 1999). The acoustic behavior of individuals are used to idicate their specific age, sex, or sexual maturity (Cranford 1999).

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