Effects of Age and Size at Metamorphosis on Performance and Metabolic Rates of Southern Toad, Bufo terrestris, Metamorphs

1. Southern Toad, Bufo terrestris, tadpoles were reared at two temperatures and two food levels in a 2 x 2 factorial design. Effects of treatments on age and size at metamorphosis, metabolic rate (MR), sprint speed and endurance of metamorphs were measured. 2. Across all treatments, MR, sprint speed and endurance were negatively related to age at metamorphosis and positively related to mass at metamorphosis. Therefore, decreases in larval period duration and increases in mass at metamorphosis may be advantageous in terms of locomotor performance, but disadvantageous because of the cost of increased energy expenditure on maintenance, all else being equal. 3. After removing the effects of age and size at metamorphosis, neither of the treatments nor their interaction significantly affected locomotor performance. In contrast, MRs of metamorphs were significantly affected by the interaction between the food and temperature treatments, independent of age and size at metamorphosis. Thus, aspects of the larval environment may affect metamorph physiology, and possibly fitness, via mechanisms other than differences in age and size at metamorphosis.