Energy stores are essential for the overwinter\r<br />survival of many temperate and polar animals, but individuals\r<br />within a species often differ in how quickly they deplete\r<br />their reserves. These disparities in overwinter performance\r<br />may be explained by differences in their physiological and\r<br />behavioral flexibility in response to food scarcity. However,\r<br />little is known about whether individuals exhibit correlated\r<br />or independent changes in these traits, and how these phenotypic\r<br />changes collectively affect their winter energy use.\r<br />We examined individual flexibility in both standard metabolic\r<br />rate and activity level in response to food scarcity and\r<br />their combined consequences for depletion of lipid stores\r<br />among overwintering brown trout (Salmo trutta). Metabolism\r<br />and activity tended to decrease, yet individuals exhibited\r<br />striking differences in their physiological and behavioral\r<br />flexibility. The rate of lipid depletion was negatively\r<br />related to decreases in both metabolic and activity rates,\r<br />with the smallest lipid loss over the simulated winter period\r<br />occurring in individuals that had the greatest reductions in\r<br />metabolism and/or activity. However, changes in metabolism\r<br />and activity were negatively correlated; those individuals\r<br />that decreased their SMR to a greater extent tended\r<br />to increase their activity rates, and vice versa, suggesting\r<br />among-individual variation in strategies for coping with\r<br />food scarcity.
Auer, S. K., Salin, K., Anderson, G. J., & Metcalfe, N. B. (2016). Flexibility in metabolic rate and activity level determines individual variation in overwinter performance. Oecologia, 182(3), 703–712. https://doi.org/10.1007/s00442-016-3697-z