The relax-hurry spectrum: Specific somatic maintenance depends on seasonal dynamics of food

Analysis of the Add-my-Pet (AmP) database reveals that specific somatic maintenance varies widely across the animal kingdom, reflecting the co-evolution of animal metabolism and environmental dynamics. Here, we stylize this range along a relax-hurry spectrum. The hurry strategy is characterized by elevated specific somatic maintenance costs, which structurally facilitate rapid growth and reproductive responses to transient resource pulses; however, this strategy is inherently wasteful in its use of resources. Conversely, the relax strategy is defined by low somatic maintenance, low growth, and increased longevity, resulting in efficient use of resources in stable environments. Several small-bodied taxa with low somatic maintenance lack a heart. Those with high somatic maintenance, i.e. annelids, cephalopods and vertebrates, have capillaries. This links a parameter value to the body plan. This study utilizes DEB parameter estimates from the AmP collection to demonstrate that seasonal or stochastic fluctuations in food availability select for the hurry strategy, whereas stable environments favor the relax strategy. Empirical evidence in various taxa supports this coupling: reef-associated ray-finned fish exhibit lower somatic maintenance than their pelagic or demersal counterparts; tropical or pelagic chondrichthyans have lower maintenance costs than temperate coastal skates; and mammals subsisting on constant foliage show lower maintenance than those dependent on seasonal seeds and fruits. Similarly, filtering bivalves and herbivorous tortoises exhibit less maintenance than more active or carnivorous mollusks and turtles. The distribution of specific somatic maintenance across all 7325 AmP species follows a mixture of two Weibull distributions. The two scaling parameters are typical values for the specific somatic maintenance for relax and hurry species. Their ratio of 38 was also found for the median values of caecilians as relax species and their prey annelids as hurry species; more typically hurry species will prey on relax species. Since hurry species are more sensitive to pesticides, and industrial crop production selects for hurry species, our recommendation for small scale biological crop production is to optimize conditions for relax species.