Movement distances and density estimation of small mammals using the spool-and-line technique

MENDEL, S.M.; VIEIRA, M.V. 2003. Movement distances and density estimation of small mammals using the spoll-and-line technique. Acta Theriologica 48(3):289-300.

Abstract. Edge effect is an inherent problem when using trapping grids to estimate density of small mammals, resulting in a sampling area larger than the area of the grid. Distances between captures of individuals are used to estimate A(W), the effective sampling area of a trapping grid, but grid size sets a limit for the largest detectable distance. The spool-and-line technique is proposed here as a new method to estimate A(W). Movement distances based on the spool-and-line technique were compared to similar movement distances based on capture-recapture of three spacies of marsupials of the Atlantic Forest of Brazil. Distances based on the two methos were uncorrelated, and only ln-transformed distances based on the spool-and-line were normally distributed. The maximum distance moved (MaxD) estimated by the spool-and-line was chosen as the more accurate and practical distance to estimate edge effect. Estimates of the effective sampling area and densities for the common opossum Didelphis aurita (Wied-Neuwied, 1826), were compared using MaxD based on spool-and-line (MaxDspool), capture-recapture (MaxDcap), and also the distance between traps (DT). MaxDspool reflected more accurately density variation between seasons. Movement distances of small mammals based on the spool-and-line technique permit more accurate estimates of density and its dynamics.

Fotos: Oxymycterus quaestor

Roedor de porte mais avantajado (os indivíduos que foram capturados nesta ocasião tinham entre 71 e 105 gramas), caracterizam-se por comportamento fossorial (ocorrem essencialmente no solo). Possuem unhas grandes, focinho alongado e cauda curta. Todos os indivíduos da amostragem foram capturados às margens do rio Marmeleiros, em Barracão.
Espécie: Oxymycterus quaestor (rato-focinhudo).
Fotógrafo: Maury S.L. Abreu.
Contato: maury.abreu@gmail.com.

VI Congresso Brasileiro de Mastozoologia - Segunda Circular

A Sociedade Brasileira de Mastozoologia divulgou, através da Segunda Circular do VI Congresso Brasileiro de Mastozoologia, as regras para submissão de propostas de conferências, mesas redondas e mini-cursos (até 10 de agosto de 2011). Faça download do arquivo para maiores informações.
O VI Congresso Brasileiro de Mastozoologia ocorrerá em 2012 na cidade de Corumbá, MG.

Estimating the abundance of mouse populations of known size: promises and pitfalls of new mothods

CONN, P.B.; ARTHUR, A.D.; BAILEY, L.L.; SINGLETON, G.R. 2006. Estimating the abundance of mouse populations of known size: promises and pitfalls of new mthods. Ecological Applications 16(2):829-837.

Abstract. Knowledge of animal abundance is fundamental to many ecological studies. Frequently, researchers cannot determine true abundance, and so must estimate it using a method such as mark–recapture or distance sampling. Recent advances in abundance estimation allow one to model heterogeneity with individual covariates or mixture distributions and to derive multimodel abundance estimators that explicitly address uncertainty about which model parameterization best represents truth. Further, it is possible to borrow information on detection probability across several populations when data are sparse. While promising, these methods have not been evaluated using mark–recapture data from populations of known abundance, and thus far have largely been overlooked by ecologists. In this paper, we explored the utility of newly developed mark–recapture methods for estimating the abundance of 12 captive populations of wild house mice (Mus musculus). We found that mark–recapture methods employing individual covariates yielded satisfactory abundance estimates for most populations. In contrast, model sets with heterogeneity formulations consisting solely of mixture distributions did not perform well for several of the populations. We show through simulation that a higher number of trapping occasions would have been necessary to achieve good estimator performance in this case. Finally, we show that simultaneous analysis of data from low abundance populations can yield viable abundance estimates.

Fotos: Nasua nasua

Este é o Chico, um quati domesticado que vivia aprontando em Aracuri. Uma verdadeira praga, mexia nas mochilas em busca de isca (e comia as luvas de procedimento que estavam sujas de isca), e até aprendeu a abrir as portas pra nos atazanar. Depois de um tempo, ele de repente sumiu. Mas pela foto até parece um animal silvestre...
Espécie: Nasua nasia (quati).
Fotógrafo: Maury S.L. Abreu.
Contato: maury.abreu@gmail.com

Geographic range and body size in Neotropical marsupials

OLIFIERS, N.; VIEIRA, M.V.; GRELLE, C.E.V. 2004. Geographic range and body size in Neotropical marsupials. Global Ecology and Biogeography 13:439-444.

Abstract.
Aim. Our aim is to investigate the relationship between body size and geographical range in Neotropical marsupials, considering the possible effects of latitude and phylogeny.
Location. Neotropical region.
Methods. Phylogenetic generalized least-squares regression method (PGLS) is used to investigate the relationship between body size, geographical range, and latitude considering the phylogenetic relationship between species. Data for 22 species were compiled from the literature.
Results. The scattergram of body size vs. geographical range was triangular in shape. Body size and geographical range were positively correlated throughout the phylogeny. Latitude was not important to this relationship.
Conclusions. The polygonal relationship between geographical range and body size seems to be moulded by ecological and geographical constraints rather than by a common association with latitude.