She is a motherly character who coordinates Tod's adoption by Widow Tweed, and later advises and cares for Tod while he is growing up. She possesses a great deal of wisdom and is generally friendly to everybody.
Big Mama is the first to discover the newly orphaned Tod and is quick to comfort the young fox. Together with Dinky and Boomer, she arranges for Tod to be adopted by Widow Tweed. When Tod grows older, she takes notice of the irony of Tod's best friend being Copper, who is his natural enemy. When Copper is taken away on a hunting trip, Big Mama takes Tod aside and explains the dangers of his friendship with Copper and warns Tod that if he and Copper were still friends, he get killed. Big Mama shows Tod the numerous animal skins that Copper's owner Amos Slade has hunted down, and tells Tod that Copper will be a trained hunting dog when he returns, and thus a danger to Tod. Tod initially rejects Big Mama's advice, claiming that Copper would never hunt him.
When the adult Tod is released into the wild, Big Mama flies to the forest. While searching for Tod, she finds Vixey, a vixen who grew up in the woods. Big Mama arranges for the two to meet, as Tod has no idea how to survive in the wild.