well, I'm just following what written on the 1st page from the rawsThe "わたまるず" (Watamaruzu) is an acronym for "Watagumo Animals" (watagumo, lit. "cotton cloud" is another name for cumulus clouds in Japanese), while also carrying a double meaning of "Watamaru & friends"
Personally I would translate it as something like "Watamals" to show that it's an acronym