A demographic analysis of population responses to the manipulation of adult males in Calomys venustus (Rodentia, Sigmodontinae)

PRIOTTO JOSÉ; GOMEZ DANIELA; POLOP JAIME

Ecological Research

Springer

Año: 2010 p. 1 - 9

0912-3814

Abstract Adults play an important role influencing the survival and/or reproduction of juveniles in many species of mammals. Adult males could have a negative effect on population density when their absence becomes a limiting factor in female fertilisation. We tested the hypotheses that the absence of overwintering males (adult males) reduces the population growth rate through a delay in the onset of reproductive activity of Cohort 1 females in Calomys venustus populations. The study was carried out in two control and two experimental enclosures (0.25 ha). Adult males were removed after their offspring were born. Weekly trapping sessions were carried out from spring to autumn. To estimate population growth rates (λ), apparent survival ( ) and seniority probability (γ) were estimated using capture-mark-recapture models. Models were constructed with these two parameters and recapture probability (p) constrained to vary as a function of time, enclosure and/or treatment. We derived estimates of population growth rates through the estimates of and γ. The best models for and γ did not show treatment effect. Variability between the four enclosures was greater than between control and experimental enclosures. Enclosures had different growth rates at the beginning of the study but were equalled at the end. Temporal variation in population growth rates was a result of temporal variation of γ. The two controls showed the highest growth rates earlier in time. The results did not support the hypothesis tested in this study. It seems that the number of overwintering males do not affect the population growth rate.