AUCO LONG-TERM ECOLOGICAL RESEARCH site

Research Highlights

Conservation and implications

The conservation of biodiversity in Auco
In Auco, four strigiform, six falconiforms, and two fox species joined the suite of endothermic vertebrate predators at various times from 1987 to 1994. Different falconiforms entered and exited the suite at times roughly correlated with long-term fluctuations in the density of small mammals (which in turn were roughly correlated with long-term climatic cycles), but strigiforms and foxes remained resident throughout the seven years.
Using detailed data on diets (trophic guild structure) and on residence status of the 12 predator species, we assessed whether the combination of these two criteria, if obtained in a shorter study, would have been adequate to make reasonable decisions were it possible to conserve only a subset of those species. In particular, we evaluated whether ecological redundancy as gauged by high diet similarity, would provide a reasonable basis for concentrating on the conservation of some species more than others. Guild structure of the predator suite at Auco remained quite consistent through the first three years of the study but then shifted markedly, such that conservation strategies based on apparent ecological redundancy (in diet) early on would have been misguided in the long term.
Although transient species sometimes were redundant with residents, in other years the same transients played unique trophic roles, such that the apparently rational strategy of concentrating conservation efforts on less mobile, resident species would have left gaps in ecosystem function. Likewise, a short-term, intensive inventory of Auco's predators would have underestimated in some years, and overestimated in others, the richness of species depending on prey resources there. We conclude that no short-term data would have provided adequate bases for focusing conservation efforts on some species or particular habitat patches. While realistically no such decision-making process can be delayed until a seven-year (or longer) data set has been accumulated, we suggest that short-term studies of species assemblages be used very cautiously when making conservation decisions.
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On lessons about biodiversity in arid environments subjected to ENSO events
In the first seven years (1987-1994) of our ongoing study on vertebrate predators and their prey in Auco, supra-annual fluctuations in biodiversity have greatly exceeded seasonal fluctuations. Out of a total of twelve predator species (six falconiforms, four strigiforms, two foxes), only three have been present on the study site throughout; at any one time the total species richness has ranged from five to ten. Likewise, the prevalent prey base of small mammals irrupted at the onset of the study, in 1987, but declined markedly both in numbers and species richness during the ensuing, unusually dry years, rebounding to "typical" levels when "typical" rainfall patterns returned in 1991. Clearly, supra-annual climatic features have reverberated throughout functional linkages in this aird ecosystem, all the way to the level of top predators. Thus, "typical" is a misnomer: the driving forces have been atypical events (e.g., the 1987 El Niño Southern Oscillation) likely to have been missed by a short- or medium-term study. The data set, focusing on species of categories often termed "charismatic," "keystone," "umbrella," and/or "flagship," also offers caveats to management decisions based on short-term studies or "typical" conditions, which may inadvertently misrepresent the conservation needs or realities of some species of most concern.
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