Biologists have long been interested in the physiological mechanisms that mediate longevity in animals. One of the theories regarding aging and longevity in animals is Raymond Pearl’s rate of living theory, which postulates that heightened level of metabolism leads to an increased rate of aging and reduced lifespan in animals. The theory has received ample support from studies in ectotherms, but it is widely challenged in endotherms. The Damaraland mole rat (DMR; Fukomys damarensis) is a long-lived eusocial mammal. They can live in captivity for more than 20 years. They maintain stable body composition and only show slight age-related changes in physiological and morphological characteristics. Conversely, the Siberian hamster (SH; Phodopus sungorus) exhibits longevity typical of other rodents. We capitalized on these unique animal models and re-visited the rate of living theory by comparing bioenergetics of DMR and SH at the mitochondrial, cellular, and organismal levels. Preliminary analysis showed that both mitochondrial and cellular respirations were lower in DMR compared to SH. Basal metabolic rate (BMR) was also lower in DMR compared to SH. Additionally, BMR was not different between DMR of different ages. These findings support the rate of living theory and suggested that the extreme longevity of DMR could be attributed to their low metabolic rate. Data on other bioenergetics measurements from both species will be presented at the meeting.