Characterizing the starvation syndrome in the western diamond‐back rattlesnake, a species well‐suited to tolerate long‐term fasting

Abstract

The starvation syndrome refers to the suite of physiological responses that result from food resource limitation. Although some reptiles are recognized for their ability to tolerate periods of fasting that are prohibitive for many other animals, very little is known about the mechanisms that reptiles employ to physiologically cope with the pressure of starvation. The purpose of this study was to characterize the starvation syndrome in a snake species that is well known to tolerate long periods of fasting. I measured changes in mass, resting metabolic rate, hematocrit, circulating glucose and ketone bodies over a fasting period of 168d. I also quantified changes in tissue composition, mineral content, fatty acid profile, and amino acid composition as well as changes in 15N isotope signature of proteins. The results of these analyses reveal that fasting snakes experienced a 30% reduction in body mass, a 64% reduction in blood glucose, and a 70% increase in plasma ketone bodies during this period. Selected organs did not show significant reductions in wet mass, but fasting animals increased total water content from 70% to 74% that worked to reduce rates of whole body mass loss and ultimately masked losses in organic mass during starvation. Whole animal and mass specific resting metabolic rates reduced by 75% and 65% respectively, and the blood of starved snakes showed a decrease in hematocrit. The 15N isotope signature of excreted nitrogen demonstrated a 1–2 per mil enrichment, and starvation-induced changes in whole body fatty acid and amino acid composition revealed possible mechanisms for protein and lipid sparing in these animals.