Assessing the impact of owl predation on the growth rate of a rodent prey population

KITTLEIN, MARCELO J.

ECOLOGICAL MODELLING

Elsevier

Año: 1997 vol. 103 p. 123 - 134

0304-3800

Data from a comparative survey of rodent population dynamics and predation by owls were used to estimate theimpact of owl predation on the demography of the sigmodontine rodent Akodon azarae. A stage-structured matrixmodel based on mass classes was used to estimate rodent demographic parameters through the analysis of fieldestimated transition matrices. Owl pellet analysis allowed estimation of predation rate upon different mass classes ofA. azarae and computation of estimated predation-free transition matrices. Owl predation affected exclusively smallindividuals of initial body mass stages. Although population growth rate in A. azarae was most Sensitive to transitionsinvolving initial stages, exclusive consumption of small individuals by owls did not have a significant impact onpopulation growth rate. Owls preyed upon individuals of A. azarae only slightly, possibly on account of specificfeatures of its habitat use and escape response, which may result in predators not affecting prey abundance ordemography. The proposed methods can be of special convenience for endangered or rare vertebrate species in whichlarge-scale experimental manipulations might be questionable.