Body weight, metabolic rate, and trace substance turnover in animals

Consequences of size-dependent metabolic rate on the turnover of trace substances in animals are investigated. At steady state, the biological half-life, body burden, and whole body concentration of a trace substance are shown to be proportional to body weight raised to (1-b), 1, and 0, respectively, where b is the exponent relating body weight to standard metabolic rate. The condition is that the trace substance is turned over in proportion to the standard metabolic rate; the derived equations can accordingly be used to test whether a given substance is feasible as a tracer of energy flow in ecologic systems.