Such is their fecundity that it has been asserted that one female (probably of P. vestimenti) may in eight weeks produce five thousand descendants.
Columella regarded the gains from the births as a sufficient motive for encouraging these unions, and thought that mothers should be rewarded for their fecundity; Varro, too, seems to have taken this view.
That chinchillas have not under such circumstances become rare, if not extinct, is owing to their extraordinary fecundity, the female usually producing five or six young twice a year.
Viability, by which are meant fecundity, longevity and vigour, was low in average.
Both social traditiolis and the religious beliefs of the people encouraged fecundity.