Tankho is a character female member of the Lenape Mice, appearing in An American Tail: The Treasure of Manhattan Island.
Role in the Film 
Tankho is a tall and beautiful member of the tribe. She takes an immediate liking to Scuttlebutt, giving him huge hugs, though he is less than receptive to her advances. During the Lenape welcoming ceremony Scuttlebutt sneaks off to steal things, and when Tankho goes looking for him and discovers him in one of their tents, she punches him straight into the air and he lands in their watermelon patch. She is heartbroken and in tears after this.
After this she can be seen in the background a few times, most notably at the end of the film when Cholena and Chief Wulisso appear through a secret panel in a statue in Central Park to bid Fievel farewell from afar.
While her relationship to Cholena is unknown, the fact that she traveled with her and Chief Wulisso to the surface suggests she could be someone very close, perhaps even her big sister.