Hayo
@TheLilly789, congrats on the baby Otters! So cute! There are generally unique social theatres for juveniles in species that have interactions, or different idle/gimmick animations for juveniles and adults of a species.
In most species, juveniles will also try to follow their parent (in most cases it's the mother, though in species where the male raises the young they'll try to run after the father, such as the Cassowary and Ostrich).
Gameplay-wise, we'd say one of the biggest difference between juveniles and adults are the Penguins and Seals as the juveniles are not able to go into the water at all!