On the Animals living on Yggdrasill
“In the poetic imagery of Yggdrasill several animals exist that represent the various powers of the cosmos. In Niflhel are the serpents that represent the corruption of Chaos as they constantly gnaw away at the ordered creation.
Four harts nibble at the crown of the tree, whose names denote slumber and death and thus symbolize the ‘otherworldly’ concepts of sleep, dreams, and the afterlife. In Yggdrasill’s branches sits an eagle that knows many things, and is likely Odin himself in the guise of a bird. Between the eagle’s eyes sits a hawk called Vedrfolnir, ‘The Weather-Bleached,’ and near them is the cock Vidofnir ‘The Wide-Open,’ probably representing the Asagods who look over and protect the worlds. A squirrel named Ratatosk ‘Rati’s Tooth’ runs up and down the tree, carrying messages between the eagle and Nidhogg ‘The Underworld Serpent.’ This squirrel is likely a symbol of Heimdall, who protects the tree and all the worlds, vigilantly keeping the balance between order and chaos. Consequently, Heimdall is also God of the Hearth-Fire (hence his name: 'Home-Light') and the Need-Fire which protects the home and the ceremonial space.
The point of examining these symbols is to show how our ancestors viewed the universe as a living organism, rather than simply an empty, mechanical structure.
Certain mechanisms were put into place to keep the order moving, as we shall see, but we know that there is so much more to it all than what one can view through a telescope. Everything in the cosmos is alive, and everything is connected in one way or another. Yggdrasill represents this connection; the vast ecosystem in which all of us, including the Gods, live and thrive.”
Odisbook: The Book of Odr