"Mammals do not lay eggs."
Translation:Mamuloj ne demetas ovojn.
Demeti is a compound word, which Esperanto - being an agglutinative language - has many of. So trying to look up the compound doesn't quite work. De, as you know, means "of, about, pertaining to."
Meti (= put, lay, place, set) is related to the Spanish and Portuguese word meter, the Italian mèttere, the French mettre, and the Occitane metre all apparently derived from the Latin mittere = "to send". As we well know, words can shift meaning as they travel through other cultures. Google translate says that all of those non-Latin words mean "to put," or, maybe, to lay (down). So maybe Cherpillod may be mistaken & Styles is right.
So demeti means "to put something on something else" Demetu la libron surtable, Mi demetis la ŝlosilojn akurate ĉi tie! la kokino demetas ovojn en sia nesto. Mi demetus tiun temon.
I hope that this helps someone.
You're always right to report anything where you even suspect that you are right. If you are, they will thank you and make fixes. if you aren't you'll never hear from them again.
It is all volunteer work and on personal time, so they don't mean to be brusque.
As for your question about de/metas: I'm not sure why the difference between the two critters. Every dictionary which I checked has demeti ovon while the simple meti = "put, lay (down), place, set, etc." I suspect that if there is an error it's with the alligators.
Though reading what Salivanto wrote to AveryMH, there very likely is no error.