Population size
Population size is subject to large swings. In 1990, there was a mass seeding event when over a million hectares of the bamboo "Chusquea valdiviensis" in southern Chile flowered simultaneously; the enormous quantities of seeds produced were followed by a population explosion of "O. longicaudatus". Such increases in rodent numbers are the result of greater fecundity, a higher survival of juveniles and a lengthening of the breeding season. Since many of the bamboo seeds were retained within the flowering spikelets till the following year, further rodent population peaks occurred then.