Weasel and otter... I cannot imagine how spartan beasts look like that. I saw tons of beast spartan warriors based on big cats mostly. Lion, black panther, jaguar, lionesses, even tigers. But weasel and otters in spartan arena...? Never heard of it. Maybe Yugioh is pretty unique and special case for having Gladiator beasts. Hmm I don't think Gladiator Beasts got weasel or otter warriors yet.
Speaking about weasel, how about civet? There is a chinese anime called "Soul Land", they have female character with "speed power" and have black color too. Her spirit is civet, what do you think about it? Is it possible if it is a civet?