Earthworms produce a collagen-like substance detected by the garter snake vomeronasal system.

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Abstract
Earthworms (Lumbricus terrestris) produce a chemical substance that is readily detected by and serves as an attractant for garter snakes (Thamnophis sirtalis). This chemoattractant is sensed by the vomeronasal system of snakes. Amino acid analysis of the chemoattractant revealed a high hydroxyproline/proline ratio and large amounts of serine and threonine. More than one-third of the residues were glycine. No hydroxylysine and no cysteine were present. Carbohydrate analyses revealed a high content of galactose (11% by weight) and smaller amounts of fucose, mannose, glucose, N-acetylglucosamine, and N-acetylgalactosamine. These results were very similar to results reported for the amino acid composition and carbohydrate content of earthworm cuticle collagen and gelatin. A preparation of purified earthworm cuticle collagen proved to be a potent source of chemoattractant for garter snakes. Further, it was not possible to prepare chemoattractant from decuticlized earthworms. These results strongly suggest that a component of the earthworm chemoattractant for snakes is structurally related to earthworm cuticle collagen.