In the Poetic Edda poem Grímnismál, the god Odin (disguised as Grímnir) says that Ratatoskr runs up and down Yggdrasil bringing messages between the eagle perched atop it and Níðhöggr below it:
Benjamin Thorpe translation:
Ratatösk is the squirrel named, who has run
in Yggdrasil's ash;
he from above the eagle's words must carry,
and beneath the Nidhögg repeat.[6] Henry Adams Bellows translation:
Ratatosk is the squirrel who there shall run
On the ash-tree Yggdrasil;
From above the words of the eagle he bears,
And tells them to Nithhogg beneath.[7]
In the Prose Edda book Gylfaginning, Ratatoskr is attested in chapter 16. In the chapter, Gangleri (described as king Gylfi in disguise) asks High what other notable facts there are to know about Yggdrasil. High's account agrees with the Grímnismál attestation but he adds that the messages are slanderous gossip:
'There is much to be told. An eagle sits at the top of the ash, and it has knowledge of many things. Between its eyes sits the hawk called Vedrfolnir [...]. The squirrel called Ratatosk [...] runs up and down the ash. He tells slanderous gossip, provoking the eagle and Nidhogg.'
