What squirrel carries messages up and down Yggdrasil?

The squirrel that carries messages up and down Yggdrasil is Ratatoskr. In Norse mythology, this small creature runs along the world tree between the eagle above and the dragon Níðhöggr below.

Ratatoskr appears in the Poetic Edda poem Grímnismál, where the squirrel is described as carrying messages between the eagle and Níðhöggr. Snorri Sturluson’s Prose Edda gives the animal a more mischievous character, saying it spreads slanderous gossip and provokes the two creatures against each other.

The name Ratatoskr is generally explained as meaning something like “drill-tooth” or “bore-tooth.” The squirrel is sometimes mistakenly identified with Vedrfolnir, the hawk sitting between the eagle’s eyes, or with Níðhöggr, the serpent-like dragon beneath Yggdrasil. Ratatoskr is distinct from both: its defining feature is movement through the tree and communication between its opposing regions.