Life Histories of Mammals: Analyses Among and Within Spermophilus Columbianus Life Tables

Ecology: Vol. 68, No. 5, pp. 1351–1363, by Richard M. Zammuto. 1987.

Abstract. Eleven theoretical predictions (or assumptions) of life history evolution are considered for the montane Columbian ground squirrel, Spermophilus columbianus, using age—specific survival and fecundity from six life tables of natural populations. The following statements are supported among age classes among populations, among age classes within populations, and (or) within age classes among populations: (1) mortality rates are high after birth, drop to a minimum by age 1 yr, and then rise with age; (2) fecundity increases with age and seldom decreases at the last age reproduction; (3) reproductive value and residual reproductive value rise to a peak and then fall with age; (4) age—specific mortality rate and age—specific mortality covary inversely with reproductive value; (5) residual reproductive value, survival, and survival rates covary inversely with fecundity; (6) residual reproductive value is positively correlated with adult survival; (7) no relationships were found between fecundity and successive survival probabilities in the life table; (8) no relationship was found between age at maturity and life expectancy; (9) no relationship was found between litter size and generation length; (10) future fecundity is positively correlated with present fecundity; and (11) age—specific fecundity varies inversely with modified reproductive value. Life history patterns among populations, within populations, within age classes, and among species are not always similar, so that theoretical predictions should explicitly delineate the level of organization to which they pertain.

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