In a cool environment, an ectotherm is more likely to survive an extended period of food deprivation than would an equally sized endotherm because the ectotherm . In a cool environment, an ectotherm is more likely to survive an extended period of food deprivation than would an equally sized endotherm because the ectotherm . expends more energy per kilogram of body mass than does the endotherm has greater insulation on its body surface maintains a higher basal metabolic rate invests little energy in temperature regulation