Low production "efficiency" of homoeotherm populations: a misunderstanding.

The production/respiration (P/R) ratios of homoeotherm populations are about one order of magnitude lower than those of poikilotherm populations. This has suggested to ecologists that homoeotherms are much less efficient converters of food energy into growth and reproduction than poikilotherms, the reason being the high cost of thermal homoeostasis. That this conclusion is wrong can be demonstrated by plotting three measures of production: individual growth rate; maximum rate of population increase; and natural rate of population increase, against rate of basal netabolism. It follows that to call the P/R ratio of communities a measure of production "efficiency" leads to confusion. If the P/R ratios of homoeotherm poulations are lower than those of poikilotherm populations it is not because their individual members are less "efficient" but because the low rate of natural increase happens to have been the most stable evolutionary solution for the organization of life cycle schedules in these animals.