Stavanzer

A Stavanzer (Trannish for "Thunder-Eater") is a colossal species of non-sapient slug-like life forms which roam over the frozen landscapes of planet Tran-ky-ky while feeding on the succulent vegetation known as pika-pedan.

Biology
Stavanzers are gigantic slug-like creatures with slate-grey armored skin and low-set eyes. An aged individual can reach over 100 meters in length. Their undersides consist of a horny pad, rendered smooth by friction against the ice below, and described as thicker than a spaceship's hull. They can be found moving either in herds or alone.

Stavanzers move by inhaling large quantities of air, which is pressured and expelled by two openings at the tail-end of their bodies, providing propulsion. They have only two teeth, which are massive in size, and swallow anything on their way, although they favor vegetation. Although the mouth is gargantuan, the throat itself is proportionally small.

Every forty thousand years, as Tran-ky-ky approaches its sun and the ice oceans melt, the Stavanzers acquire gills and become aquatic. This warm cycle lasts for about ten thousand years and is followed by another glacial period of thirty thousand.

Cultural significance
Due to their massive size, the Stavanzer is the most feared creature on Tran-ky-ky, so large that the native Tran can rarely hope to be able to kill them and usually settle for driving them away (itself a difficult and dangerous task) when they wander in the direction of a city. Fortunately, a herd of Stavanzers is usually far safer than a lone individual, as the herd will be more interested in feeding and is unlikely to get curious about things like cities and caravans.

The ivory tusk of a Stavanzer is large enough that it can be carved into sculptures, thrones and other luxury articles.

Appearances

 * Icerigger, by Alan Dean Foster (1974)
 * Mission to Moulokin, by Alan Dean Foster (1979)
 * The Deluge Drivers, by Alan Dean Foster (1987)