What do mysticete songs mean? Ask a hippo.

Given their phylogenetic proximity,
in the large reptile tree (LRT, 2196 taxa), and lack of any extant transitional taxa, if you’re going to study mysticete (whale) songs, you might want to study hippo sounds first. They and their songs are more primitive and more accessible.

Hippos and mysticetes share a last common very vocal extinct ancestor.
Hippos can be loud, reaching 115 decibels (= an AC/DC rock concert). Hippos can send their sounds through river water where it reaches other pods of hippos. When hippos are more mellow and their neighbors are bumping into each other, hippos produce squeals, grunts and clicks. Same with mysticetes.

Why do mysticetes sing, grunt and click?
Like hippos (and all mammals), mysticetes are social animals, interacting with each other for dominance, territory, protecting and raising young, friendship, sex and the self-expression of transient minor emotions.

Extrapolations?
Given that oreodonts, mesonychids, anthracobunids and desmostylians (Figs 1, 2) are all extinct clade members in the LRT along with extant mysticetes and hippos, phylogenetic bracketing gives these extinct taxa similar vocal abilities above and underwater.

We’ve already discussed odontocetes
and their ability to echolocate (low and high frequency clicks). This ability is shared with small, terrestrial tenrecs from Madagascar. It’s a different ability for that clade because odontocetes are not related to mysticetes in the LRT.

More videos
of angry hippos here on YouTube.