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Revista Brasileira de Zoologia

Print version ISSN 0101-8175

Rev. Bras. Zool. vol.16 no.4 Curitiba  1999 

A field comparison of two capture-mark-recapture estimators of small mammal populations



Rosana GentileI,II; Fernando A.S. FernandezI

IDepartamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro. Caixa Postal 68020, 21941-590 Rio de Janeiro, Brasil. E-mail:
IIPrograma de Pós-Graduação em Genética, Departamento de Genética, Universidade Federal do Rio de Janeiro. 21941-590 Rio de Janeiro, Rio de Janeiro, Brasil




The results obtained by two estimators of population sizes, MNKA and Mh, were compared for four species of small mammmals - Didelphis aurita Wied, 1826, Philander frenata (Olfers, 1818), Nectomys squamipes (Brants, 1827) and Akodon cursor (Winge, 1887) - during a long-term population study. The MNKA estimator consistently underestimated the population sizes in relation to Mh. On the other, the probabilistic estimator Mh, which reduces bias through the jackknife technique, could not be used in all cases as its assumptions were not always met. Correction factors between the estimates obtained by the two methods were calculated for the last three species, for which catchability did not vary significantly in time and that presented positive correlation between the estimates by the two models. In order to combine the adavantages of both methods for small mammal population studies, is suggested the use of probabilistic closed population models and to calculate a correction factor based in another model which allow estimates in all cases, and which provides correlated estimates. This correction factors should be used in those cases where the probabilistic model cannot be used.

Key words: Capture-recapture, jackknife estimator, minimun number known alive, population size



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ACKOWLEDGEMENTS. We would like to thank C.E.V. Grelle and C. Horta for the help in the field work. P.S. D'Andrea for providing support and help for the field work and comments during the whole study, L. Rey and R. Cerqueira for the existence of the project, and H.G. Bergallo for comments. We also thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Rio de Janeiro (FAPERJ), Instituto Oswaldo Cruz (FIOCRUZ), and Fundação Jose Bonifácio (FUJB) for financial support.



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Recebido em 06.VIII.1998; aceito em 07.X.1999.

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