Production efficiency differences between poikilotherms and homeotherms have little to do with metabolic rate

Abstract

The idea that homeothermic populations have a much lower production efficiency than poikilothermic populations, because warm‐blooded individuals exhibit a higher metabolic rate per gram of body weight, is widespread. Using Dynamic Energy Budget (DEB) theory, in combination with a modelling exercise based on empirical data for over 1000 different species, I show that this idea is wrong. Production efficiency of homeothermic individuals can be as high or even higher than that of poikilotherms. Differences observed are merely the result of different energy allocation and life‐history strategies. Birds, for example have evolved to invest a large proportion of the assimilated energy in somatic growth and maintenance and to mature at a relatively large size. Therefore, their production efficiency as an adult is low. This low reproduction efficiency combined with a low mortality rate causes the low production efficiency of bird (and other homeothermic) populations.

Diaspis echinocacti (Hemiptera: Diaspididae) on cactus pear cladodes: biological aspects at different temperatures

“…The development of most individuals of this insect, composed of females at all temperatures and their males only between 25 ºC and 30 ºC can be attributed to changes in the sex ratio of the progeny, common in Coccidae species (El-Awady et al, 2021). The shorter period of egg-nymph and egg-adult stages of D. echinocacti females and males fed with cactus pear cladodes as the temperature increased was expected, as this parameter is inversely correlated for poikilothermic organisms, such as insects (Van Der Meer, 2021). Temperature increase accelerate metabolism and, consequently, movement, fecundity, population size and geographic distribution, but reduces longevity of insects (Hamblin et al, 2017;Just and Frank, 2020).…”

Power and Efficiency in Living Systems

“…A key point is that in endotherms, heat is not merely lost as useless energy; rather, it is essential for maintaining high body temperatures that permit exploitation of cold habitats and nocturnal time periods and that support enhanced rates of muscular activity, food acquisition, digestion, growth, reproduction, and parental care [261,484,[487][488][489][490][491][492][493][494][495][496][497]. Heinrich [498] has argued that the maintenance of high, nearly constant body temperatures in many endothermic animals increases the efficiency of their biochemical reactions. In addition, young individual endotherms and ectotherms have comparable efficiencies of converting assimilated energy into growth [82,134,200,499], though during early ontogeny, both endotherms and ectotherms tend to be relatively ectothermic.…”

“…In short, high-powered endotherms are not necessarily less efficient than ectotherms (also see Section 8.2.3 and [134,245,499,520]). Endothermy has permitted increases in two useful outputs: (1) heat production for thermoregulation enabling increased metabolic power and environmental temperature tolerance [487,492,498] and (2) biomass production for increased rates of growth and reproduction [198,317,486]. Viewed this way, heat production is not just a metabolic waste but a means for increasing energetic power, functional performance, and exploitation of a wide range of resources and habitats.…”

Maintaining global biodiversity by developing a sustainable Anthropocene food production system

“…Circumventing the inefficiency of animal conversion . The transfer of energy in plant materials to animal flesh has a low conversion rate (van der Meer, 2021), commonly suggested at around 10%, with subsequent inefficiencies of conversion for each additional trophic level. Hence, much larger areas of land and volumes of water are required to obtain our energy from animals than from plants.…”