Translation

ottā means "Otter" in English.
It's a katakanization, a loan-word.

ottā is normally written with katakana, as オッター.
ottā written with hiragana is おったー.
ottā does not have kanji.
Romaji o ttaa
Katakanaオッター
Hiraganaおったー

Orthography Notes

Synonyms

kawa-uso カワウソ, uso 獺, oso 獺, datsu 獺, Lutrinae.

Further Reading

Wikipedia: 獺 (Otter)
rakko 海獺.