Metabolic theory links physiology with ecology, and successfully predicts many allometric scaling relationships. Scaling in metabolism and abundance are predicted to cancel out, with universal exponents of 3/4 and –3/4 respectively (energetic equivalence).  We tested these predictions using data from over 2000 species from eight animal Phyla.

Results/Conclusions

We find that metabolism on average scales to the 3/4 power, but abundance scaling is far shallower, at -0.58. Both allometries, however, are significantly heterogeneous, with most variation among taxonomic orders in each case. Metabolic theory cannot explain this heterogeneity, but some variation is consistent with boundary constraints on metabolism. Metabolism and abundance scaling were weakly correlated but much additional variation is explained by geometric constraints on foraging. Our findings help resolve controversy about metabolic scaling and highlight areas needing theoretical development.