The song "Nature" is a Samples cover, released for the first time in May of 1989 as the last track on their self-titled album. Also known as "The Blue Album," the record was recorded in 1989 and released that year independantly by the band. The album caught the attention of executives at Arista records, and the Samples signed their first record contract. The Blue Album was re-released on the Arista album, but the Samples left the label before recording another album, citing irreconciable differences between the band and the label. The album was released for a third time in 1991 when the band signed with fledgling What Are Records?
Dave used to sing some lyrics from "Nature" before Tripping Billies
overtop of some chords based around Tripping Billies. For this reason, this intro is known as the "Nature intro" even though it is instrumental now and therefore has no connection to the Samples song.
When the intro is listed as a separate song, it refers to an extended Nature intro whose music is still based around Tripping Billies but which has lyrics from the Samples song.