The annual cycle in body weight of small mammals from the Transvaal, South Africa, as an adaptation to a subtropical seasonal environment

Seasonal breeding of non‐hibernating small mammals is generally associated with a reduction in body weight during the non‐breeding period. In aseasonal breeders and in exceptional situations, when winter breeding occurs, this pattern cannot be found. The reduction in body weight is thought to be a means to reduce energy requirements during the harsh non‐breeding season that can either be winter, in the Holarctic, or the dry season in the Transvaal highveld. The controlling mechanism in the strongly seasonal subtropical environment in southern Africa seems to be photoperiod as in small mammals from the northern hemisphere. Since a general agreement in body weight changes was found in rodents and shrews from both areas, further similarities in adaptations to strongly seasonal environments in the subtropics are expected. For the first time it is shown that the adaptive responses of small mammals to unfavourable seasons are similar in the Holarctic and seasonal subtropical areas.