Do frugivore population fluctuations reflect fruit production? Evidence from Panama

Katharine Milton, Jacalyn Giacalone, S. Joseph Wright, Gretchen Stockmayer

    Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

    26 Scopus citations


    To conserve tropical mammals, it is important to understand factors affecting the range of population fluctuations that normally occur over both the short and long term. Annual shifts in the population size of many species may be tied, at least in part, to phenological production patterns of plants, which in turn are often affected by climatic events. To examine the influence of annual fruit crop size on population dynamics of frugivorous mammals, we compared estimates of fruit production and the relative abundance of four frugivorous mammal species (agoutis, squirrels, capuchin monkeys, howler monkeys) for 15 years on Barro Colorado Island, Republic of Panama. Species differed in the magnitude of population fluctuation. Howler monkey population estimates showed little annual fluctuation and no significant relationship to fruit production. In contrast, population estimates for agoutis, squirrels and capuchin monkeys showed interannual fluctuations, at times dramatic, but these were not always concordant nor did they necessarily appear to relate to fruit production estimates, either within years or with a one-or two-year lag. Fruit production data suggest that, on average, in any given year only 20 to 30% of the mid-to-late rainy season species producing fruits important to frugivores will have an unusually good year; other species will have an average to sub-standard year. The next year, 20 to 30% of the other important fruit species in this temporal cohort will have an unusually good year-though one cannot predict in advance which species they will be. This oscillating production pattern makes it difficult to predict, except in extreme years, how the frugivore community or individual species will be affected by fruit availability. To draw conclusions on this topic, more detailed data are required on annual fruit production patterns of a representative sample of individuals of important fruit species as well as data on reproductive and other relevant traits of each mammal species. The possibility remains that many mammal populations may be affected more immediately by top-down factors such as predators, parasites or disease rather than by bottom-up factors such as fruit availability. As population parameters for each mammal species are likely influenced by a continuously varying combination of factors, barring effects of rare environmental events, f the particular set of factors affecting the population dynamics of one frugivorous species in any given year may not necessarily impact similarly in that year on other frugivorous species at that same site.

    Original languageEnglish
    Title of host publicationTropical Fruits and Frugivores
    Subtitle of host publicationThe Search for Strong Interactors
    PublisherSpringer Netherlands
    Number of pages31
    ISBN (Electronic)9781402038334
    ISBN (Print)1402038321, 9781402038327
    StatePublished - 1 Jan 2005


    • El Niño Southern Oscillation (ENSO)
    • Fruit production
    • Panama
    • agoutis
    • mammals
    • monkeys
    • population dynamics
    • squirrels
    • tropical forests


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