From publisher blurb:
SPECIES NAME: POLYGEMINUS GREX. ORIGIN WORLD: IOTA GEMINORIUM IV
Tribbles are small furry life-forms, often regarded as unintelligent, and are native to the plant Iota Geminorium IV. They make soft, calming, purring sounds when touched, and breed at an alarming rate outside of their native world. When in close proximity to Klingons, tribbles emit a high-pitched shriek. It is suggested that due to both species having a keen sense of smell, they find each other repulsive, the main reason for their mortal rivalry.
This free PDF introduces Tribbles as player characters for the Star Trek Adventures RPG. Includes sinister new Borg Tribbles!