I’ve answered this question in commentary before but for those that missed it or don’t check the comments very often, sarnothi breast feed their infants. It’s for a much shorter duration than humans do (a few weeks to about a month). Biologically, this is to provide calcium and other minerals to the infant until their jaws are capable of crushing fish bones on their own.

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I figure Sai Fen remembers the different sounds Suko made when he was younger to identify "happy" from "hungry" pretty reliably.