Abstract: The adaptive significance of maintaining multiple color morphs within a species is the subject of much debate. Predator avoidance, habitat preference, and ecological separation have been hypothesized to explain multimodal patterns in species coloration. With increasing global warming and habitat fragmentation, it has become more important to understand how color polymorphisms affect the ecological function of organisms. We examined the adaptive significance of two common color morphs of the red-backed salamander Plethodon cinereus . An unstriped morph has increased in frequency by 6% over the last 100 years concomitant with increases in temperature. We hypothesized that differences in thermal preference and dietary composition between the striped and unstriped morphs affect their fitness differentially and are the result of foraging differences. Using fluorescent powder, we tracked salamander activity in the field and mesocosm enclosures to test this hypothesis. We failed to find any significant relationships between environmental characteristics and morph activity levels. However, unstriped individuals were found to be more active in the field and mesocosms, and had significantly better body conditions at the end of our mesocosm experiment; this suggests a fitness advantage over the striped morph over the entire range of conditions in our study. Significant, unexpected interactions were found between salamander morph and sex; striped females and unstriped males consistently performed better in field and controlled settings. Energy expenditure hypotheses are presented as possible explanations for differing performance among sex and morph, though more research is necessary to understand inter-sexual color morph function in P. cinereus.