Leopard Seals Serenade Under Antarctic Ice
Researchers Uncover Complex Vocalizations of Marine Predators
Male leopard seals employ a surprising vocal strategy to find mates in the vast Antarctic waters. During the breeding season, these apex predators engage in prolonged singing sessions, a behavior scientists are just beginning to understand.
The Sound of a Mate
From late October to early January, male leopard seals, identified by their scientific name *Hydrurga leptonyx*, dedicate hours each day to singing. This dedication is driven by the challenge of locating and attracting females in the sparse Antarctic environment. For up to 13 hours daily, they emit around 400 cycles of sound, pausing only briefly to surface for air every two minutes.
โThey are like singers in the southern ocean. During the mating season, if you drop hydrophone to water anywhere under the ice layer in this region, you will hear them singing.โ
โProfessor Tracey Rogers, University of New South Wales
The songs, first extensively recorded by **Professor Tracey Rogers** in the 1990s, have been analyzed by her student **Lucinda Chambers** using advanced techniques. Their research suggests a surprising parallel between these marine melodies and human expressions.
Decoding the Seal’s Song
Comparisons with other vocal animals and human music reveal a striking similarity in the “entropy of their information”โhow predictable or random the sound patterns are. Chambers noted, “When we compare their songs with other research on vocal animals and human music, we found that entropy of their information, the measure of how easily predictable or random the order, very similar to the poetry of our own children.” The analysis included classic children’s rhymes like “Baa Baa Black Sheep,” finding them akin to the leopard seal’s vocal repertoire, though less complex than much human music.
Leopard seals from East Antarctica, the focus of the current research, exhibit five distinct vocal patterns, or “tones.” **Professor Rogers** mentioned, “You cannot distinguish them from how the chirping sound. Although there may be something there that can only be recognized by other leopard seals that sound sexy or scary.”
A Strategy of Repetition
Unlike the elaborate songs of humpback whales, which incorporate varied timing and sequences, leopard seals appear to rely heavily on repetition. This consistent, almost monotonous style is believed to be a deliberate tactic to ensure their calls travel effectively across vast distances beneath the ice.
โThey have adjusted their style to a almost boring level, which we think is a intentional strategy, so their calls are heard far above the ice.โ
โProfessor Tracey Rogers
This reliance on sequence means their songs may not evolve significantly over time. Recordings from the 1990s bear a strong resemblance to contemporary ones, indicating a stable, enduring vocal tradition.
While male seals sing during mating season, females also vocalize, though less frequently and year-round. The purpose remains unclear, with possibilities including communication with pups or regional identification. As Chambers stated, “They have the same capacity to remember the melody.”
The energy required for this extensive singing is considerable. It’s speculated that male leopard seals may prioritize foraging before the mating season to sustain their vocal efforts. A recent study found that the average adult leopard seal consumes around 10 kilograms of food per day, highlighting the significant energy reserves needed for their mating rituals (Australian Antarctic Program).
