but they are animals, for example some animals aged diferently from the humans, they reach adulthood more fast than the others, imagine a mouse with more than one or two years and probably three years, the mouse is probably very old to continue living some more years or days so... each animal has different life spans, so tails can probably be an adult, probably a young teenager boy or a young man.
if zeta have 16 years old, let's try to multiply for a life spans of an equidna, probably for a equidna it's probably an adult but depends... what is zeta, ¿a living creature with a soul with some mechanical parts in their body or she is just a lifeless machine created by someone and reprogramed with emotions like ''belle the tinkerer''?.