Learning to starve: impacts of food limitation beyond the stress period.

Starvation is common among wild animal populations, and many individuals experience repeated bouts of starvation over the course of their lives. Although much information has been gained through laboratory studies of acute starvation, little is known about how starvation affects an animal once food is again available (i.e. during the refeeding and recovery phases). Many animals exhibit a curious phenomenon - some seem to 'get better' at starving following exposure to one or more starvation events - by this we mean that they exhibit potentially adaptive responses, including reduced rates of mass loss, reduced metabolic rates, and lower costs of digestion. During subsequent refeedings they may also exhibit improved digestive efficiency and more rapid mass gain. Importantly, these responses can last until the next starvation bout or even be inherited and expressed in the subsequent generation. Currently, however, little is known about the molecular regulation and physiological mechanisms underlying these changes. Here, we identify areas of research that can fill in the most pressing knowledge gaps. In particular, we highlight how recently refined techniques (e.g. stable isotope tracers, quantitative magnetic resonance and thermal measurement) as well as next-generation sequencing approaches (e.g. RNA-seq, proteomics and holobiome sequencing) can address specific starvation-focused questions. We also describe outstanding unknowns ripe for future research regarding the timing and severity of starvation, and concerning the persistence of these responses and their interactions with other ecological stressors.