Tribbles (Polygeminus grex) are small, non-intelligent lifeforms originating from Iota Geminorum IV. Known for their prodigious reproductive rate, these round, furry creatures emit cooing sounds while touched, which have a tranquilizing effect on the Human nervous system. Born pregnant, with sufficient food a single tribble can quickly increase its number exponentially through presumably asexual reproduction, bearing an average litter of ten every twelve hours. On their homeworld, tribble populations are kept in check by a large number of reptilian predators.