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

Gentile, Rosana; Fernandez, Fernando A.S

doi:10.1590/S0101-81751999000400020

Abstract

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.

Capture-recapture; jackknife estimator; minimun number known alive; population size

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

Rosana Gentile^I,II; Fernando A.S. Fernandez^I

^IDepartamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro. Caixa Postal 68020, 21941-590 Rio de Janeiro, Brasil. E-mail: rosana@rio.com.br

^IIPrograma de Pós-Graduação em Genética, Departamento de Genética, Universidade Federal do Rio de Janeiro. 21941-590 Rio de Janeiro, Rio de Janeiro, Brasil

ABSTRACT

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

Full text available only in PDF format.

Texto completo disponível apenas em PDF.

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.

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

Boulanger, J. & C.J. Krebs. 1994. Comparison of capture-recapture estimators of snowshoe hare populations. Can. Jour. Zool. 72: 1800-1807.
Burnham, K.P. & W.S. Overton. 1979. Robust estimation of population size when capture probabilities vary among animals. Ecology 60 (5): 927-936.
Chao, A. 1988. Estimating animal abundance with capture frequency data. Jour. Wildl. Manage. 52: 295-300.
Darroch, J.N. 1958. The multiple-recapture census: I. Estimation of a closed population. Biometrika 45: 343-359.
Efford, M. 1992. Comment - revised estimates of the bias in the minimum number alive estimator. Can. Jour. Zool. 70: 628-631.
Fernandez, F.A.S. 1995. Métodos para estimativas de parâmetros populacionais por captura, marcação e recaptura. Oecologia brasiliensis 2: 1-26.
Gentile, R. & F.A.S. Fernandez. 1999. Influence of habitat structure on a streamside small mammal community in a Brazilian rural area. Mammalia 63 (1): 29-40.
Hilborn, R.; J.A. Redfield & C.J. Krebs. 1976. On the reliability of enumeration for mark recapture census of voles. Can. Jour. Zool. 54: 1019-1024.
Krebs, C.J. 1966. Demographic changes in fluctuating populations of Microtus californicus. Ecol. Monogr. 36: 239-273.
Lin, L.I.K. 1989. A concordance correlation coefficient to evaluate reproducibility. Biometrics 45: 255-268.
Montgomery, W.I. 1987. The application of capture-mark-recapture methods to the enumeration of small mammal populations. Symp. Zool. Soc. Lond. 58: 25-57.
Otis, D.L.; K.P. Burnham; G.C. White & D.R. Dusel. 1978. Statistical inference from capture data on closed animal populations. Wildl. Monogr. 62: 1-135.
Pollock, K.H. 1982. A capture-recapture design robust to unequal probablity of capture. Jour. Wildl. Manage. 46 (3): 752-757.
Seber, G.A.F. 1986. A review of estimating animal abundance. Biometrics 42: 267-292.
Zar, J.H. 1996. Biostatistical Analysis. New Jersey, Prentice Hall, X+662p.

Publication Dates

Publication in this collection
19 June 2009
Date of issue
1999

History

Accepted
07 Oct 1999
Received
06 Aug 1998

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

[1] Boulanger, J. & C.J. Krebs. 1994. Comparison of capture-recapture estimators of snowshoe hare populations. Can. Jour. Zool. 72: 1800-1807.

[2] Burnham, K.P. & W.S. Overton. 1979. Robust estimation of population size when capture probabilities vary among animals. Ecology 60 (5): 927-936.

[3] Chao, A. 1988. Estimating animal abundance with capture frequency data. Jour. Wildl. Manage. 52: 295-300.

[4] Darroch, J.N. 1958. The multiple-recapture census: I. Estimation of a closed population. Biometrika 45: 343-359.

[5] Efford, M. 1992. Comment - revised estimates of the bias in the minimum number alive estimator. Can. Jour. Zool. 70: 628-631.

[6] Fernandez, F.A.S. 1995. Métodos para estimativas de parâmetros populacionais por captura, marcação e recaptura. Oecologia brasiliensis 2: 1-26.

[7] Gentile, R. & F.A.S. Fernandez. 1999. Influence of habitat structure on a streamside small mammal community in a Brazilian rural area. Mammalia 63 (1): 29-40.

[8] Hilborn, R.; J.A. Redfield & C.J. Krebs. 1976. On the reliability of enumeration for mark recapture census of voles. Can. Jour. Zool. 54: 1019-1024.

[9] Krebs, C.J. 1966. Demographic changes in fluctuating populations of Microtus californicus. Ecol. Monogr. 36: 239-273.

[10] Lin, L.I.K. 1989. A concordance correlation coefficient to evaluate reproducibility. Biometrics 45: 255-268.

[11] Montgomery, W.I. 1987. The application of capture-mark-recapture methods to the enumeration of small mammal populations. Symp. Zool. Soc. Lond. 58: 25-57.

[12] Otis, D.L.; K.P. Burnham; G.C. White & D.R. Dusel. 1978. Statistical inference from capture data on closed animal populations. Wildl. Monogr. 62: 1-135.

[13] Pollock, K.H. 1982. A capture-recapture design robust to unequal probablity of capture. Jour. Wildl. Manage. 46 (3): 752-757.

[14] Seber, G.A.F. 1986. A review of estimating animal abundance. Biometrics 42: 267-292.

[15] Zar, J.H. 1996. Biostatistical Analysis. New Jersey, Prentice Hall, X+662p.