Acknowledgements
This work was supported by the Conselho Nacional de
Pesquisa e Desenvolvimento Cientı´fico e Tecnolo´gico
(CNPq; process no. 402295/2005-6). The authors declare
no conflict of interest. The authors’ contributions were
as follows: C.L.d.S., coordination of field work, data collection,
analysis of results, drafting the article; C.S. and
G.V.d.V., definition of the study design, data analysis,
drafting and approval of the final version of the article;
E.F. and S.C.S., coordination of the study, approval of the
final version of the article