Summary The drivers of periodic population cycling by some animal species in northern systems remain unresolved 1 . Mysterious disappearances of populations of the Neotropical, herdforming white-lipped peccary ( Tayassu pecari , henceforth “WLP”) have been anecdotally documented and explained as local events resulting from migratory movements or overhunting 2,3,4 , or as disease outbreaks 5,6 , and have not been considered in the context of large-scale species-specific population dynamics. Here we present evidence that WLP disappearances represent troughs in population cycles that occur with regular periodicity and are synchronized at regional and perhaps continent-wide spatial scales. Analysis of 43 disappearance events and 88 years of commercial and subsistence harvesting data reveals boom – bust population cycles lasting from 20 to 30 years, in which a rapid population crash occurring over 1 to 5 years is followed by a period of absence of 7 to12 years and then a slow growth phase. Overhunting alone cannot explain the crashes, but as in northern systems dispersal during the growth phase appears to play a key role. This is the first documentation of population cycling in a tropical vertebrate.