。
Who knows.
Literal
Well-who-knows.
A single-word conversational response. さあね is a casual, slightly evasive 'I don't know / who knows / beats me.' さあ is the interjection of uncertainty, and ね softens it into a conversational shrug rather than a flat refusal to answer. Short, natural, and extremely high-frequency in spoken Japanese. The tone ranges from genuinely uncertain to deliberately noncommittal depending on context.