COSTS OF REPRODUCTION IN FEMALE MOOSE (ALCES-ALCES) AS MEASURED BY MEANS OF PHENOTYPIC CORRELATIONS

The costs of pregnancy and lactation in terms of subsequent body growt h and fecundity were studied by comparing different reproductive categ ories of Swedish female moose (Alces alces) during 1989-1992. Non-repr oducing females and females that experienced gestation but not lactati on were significantly heavier than females in the same reproductive ca tegory prior to reproduction. Production of one offspring and subseque nt lactation during the summer and early autumn were also associated w ith an average annual increase in carcass mass, although this was less pronounced than in females that only experienced gestation. By contra st, production of two offspring and successful rearing of both to the autumn resulted, on average, in a reduction of carcass mass (7%) relat ive to that of females in the same reproductive category prior to repr oduction. In female moose, while body growth was affected by the costs of lactation, future fecundity was not. Instead, future fecundity was related most strongly to the number of offspring produced during the current year. This positive association could not be attributed to var iation in individual quality in terms of age or carcass mass. The ulti mate consequences of reproduction in female moose seem to strongly inf luence the patterns of growth: adult females will alternate between ga in and loss of body mass among years, depending on the number of offsp ring produced and successfully reared through the lactation phase.