Ontogeny of vocal rhythms in harbor seal pups: an exploratory study

Abstract

Puppyhood is a very active social and vocal period in a harbor seal’s life Phoca vitulina. An important feature of vocalizations is their temporal and rhythmic structure, and understanding vocal timing and rhythms in harbor seals is critical to a cross-species hypothesis in evolutionary neuroscience that links vocal learning, rhythm perception, and synchronization. This study utilized analytical techniques that may best capture rhythmic structure in pup vocalizations with the goal of examining whether (1) harbor seal pups show rhythmic structure in their calls and (2) rhythms evolve over time. Calls of 3 wild-born seal pups were recorded daily over the course of 1–3 weeks; 3 temporal features were analyzed using 3 complementary techniques. We identified temporal and rhythmic structure in pup calls across different time windows. The calls of harbor seal pups exhibit some degree of temporal and rhythmic organization, which evolves over puppyhood and resembles that of other species’ interactive communication. We suggest next steps for investigating call structure in harbor seal pups and propose comparative hypotheses to test in other pinniped species.

Rhythm in speech and animal vocalizations: a cross‐species perspective

“…Notice how, over days, the number of categories shrinks (though see Ref. ) and the transitions from one to the other become more predictable. Figure cropped from Ref.…”

“…Figure cropped from Ref. , an Open Access article distributed under the terms of the Creative Commons Attribution Non‐Commercial License; additional details in the original paper.…”

“…Instead, these other animal vocalizations fell into their own distinct pattern, closer to a monologue or solo song in terms of hierarchical temporal structure. Ravignani and colleagues applied the same AF analysis to recordings of harbor seal pups, a species that employs vocal interactions similar to killer whales, and these recordings also yielded the same communicative AF function shape.…”

“…Having a low signal to noise ratio limits the applicability of techniques acting directly over the waveform. In these situations, an alternative is to annotate the recordings with the onset or offset times and investigate the temporal structure of these events . In this section, we present another method (in addition to the AF analyses above and other techniques described in detail elsewhere) for characterizing and comparing temporal patterns in a series of events that was recently proposed in Ref.…”

“…Vocal learners, such as harbor seals and S. bilineata bats, 45,46 are useful model species to study the potential interplay between rhythm and vocal learning ontogeny. 38,44 They may also give directions for research on early human vocal production. For instance, some species share similarities with humans in their earliest vocalizations called "babbling."…”