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Body mass dynamics and growth patterns of leaf-eared mice Phyllotis darwini in a semi-arid region of the neotropics

100%

Lima M., Bozinovic F., Jaksic F. M.

Acta Theriologica

1997

tom 42

nr 1

We report on body mass dynamics, field growth rates and age-specific growth curves for the leaf-eared mouse Phyllotis darwini (Waterhouse, 1837). Mark-recapture methods provided data for a population of P. darwini in a semi-arid region of Chile from 1987 to 1996. There were significant effects of sex, season, and slope exposure on body mass. In addition, we found significant effects of sex, mass class, and season on field growth rates. Individuals had highest growth rates during spring and summer and lowest during fall, males grew faster than females, and juveniles grew faster than adults, Growth rates of males were positively correlated with precipitation levels. This result suggests that higher somatic growth rates daring periods of unusual high precipitation may account for population outbreaks observed in this species in semi-arid regions of Chile. Age-specific growth curves of body mass for both sexes showed a strong sexual dimorphism. This sexual dimorphism in body mass may be related to a polygynous mating system and strong male-male sexual competition during breeding periods,

Delayed density-dependent and rainfall effects on reproductive parameters of an irruptive rodent in semiarid Chile

80%

Lima M., Jaksic F. M.

Acta Theriologica

1998

tom 43

nr 3

We examined the influence of density-dependent and density-independent factors on reproductive processes of leaf-eared mouse Phyllotis darwini (Waterhouse, 1837) in a semiarid region of Chile subjected to El Nino-driven precipitation. This species undergoes periodic irruptions apparently triggered by unusually high precipitation. The effects of density and precipitation were analyzed statistically regarding the following reproductive parameters: fraction of reproductive females, reproductive number (juveniles + reproductive females), per capita reproductive rates, and reproduction index based on long-term data (10 years). The fraction of reproductive females was affected positively by precipitation during the preceding winter and negatively by population density one year before. The reproduction index and the reproductive rate was positively affected by population density the previous year. In addition, the reproductive number was positively correlated with precipitation levels. The P. darwini population studied was affected by delayed density-dependent and density-independent factors in reproductive parameters. We propose that both destabilizing effects on reproductive rates of P. darwini may be major factors underlying the frequent outbreaks of this mouse observed in semiarid regions of Chile.

Ograniczanie wyników

2 Acta Theriologica

2 Jaksic F. M.

2 Lima M.

1 Bozinovic F.

1 1998

1 1997

Wyniki wyszukiwania

Body mass dynamics and growth patterns of leaf-eared mice Phyllotis darwini in a semi-arid region of the neotropics

Delayed density-dependent and rainfall effects on reproductive parameters of an irruptive rodent in semiarid Chile