Different species of mammals that vocalize usually emit similar and even recognizable vocalizations among them, but this is no so with underwater calls of phocids (true seals). In this group there are some species have very diverse repertoires of underwater vocalizations and others that only emit pulsed sounds.

Underwater vocalizations are common in most species of phocids, and most of these can be attributed to males and especially during the breeding season. Available scientific literature on phocid underwater vocalizations suggest that they are emitted by adult males during fighting behavior with other males, during defense of territories, and in accessing or attracting females.

Species using lowest vocal complexity use low frequency pulses and irregular bursts and a very limited repertoire. Phocid species that use more underwater vocal complexity have an extensive and varied repertoire, sinusoidal and noisy waveform, songs and two or more rhythmic patterns in repeated element calls.

Why do some species use very complex patterns and others less so?… there is no relationship between the complexity of these songs and calls and the phylogeny of phocid species. That is, being from a certain family, genus or group of phocids does not determine the complexity of the song underwater. The complexity of underwater vocalizations is related to the reproductive strategy used by each species.

Species that use low vocal complexity are serially monogamous, do not fight with other males, do not form breeding groups, breed on beaches or pack ice, and are subject to a higher risk of predation….. There is no need to make a lot of noise.

On the other hand, species with greater vocal complexity are promiscuous or polygamous, form breeding groups on pack or landfast ice, and have a lower risk of predation…. There’s bragging to be done.

An adult Hawaiian monk seal vocalizing underwater at Lehua Rock. Notice its throat expanding while it produces sound. Video credit: Jonathan Bird (click to watch de video).

Recording of a Hawaiian monk seal low frequency underwater vocal bout shown as a spectrogram – © Marine Mammal Research Project- University of Hawaii (click to watch the video).