Northern elephant seals (NES) are naturally exposed to extreme conditions, including prolonged food and water deprivation (fasting). NES pups are born during the spring, initially nursing for a month before they are weaned and fast for two months. During this fasting period NES pups lose about 25% of their body mass, while maintaining biochemical homeostasis and supporting muscle development. At the end of their post-weaning fasting, NES pups depart the rookeries to forage before returning in the fall for their semiannual resting haul out. The environment, especially stressful environmental conditions, can modify the methylation status of DNA, consequently regulating gene expression. We compared global DNA methylation percentages between early-fasting (1-2 weeks), late-fasting (7-8 weeks), and 0.8-year old NES pups. DNA was extracted from white blood cells collected from NES pups sampled at Año Nuevo State Park, CA, and global DNA methylation was measured using an Abcam^TM Global DNA Methylation Assay Kit. Prolonged fasting significantly increased global DNA methylation (p=0.0061) in NES pups, while 0.8 year old pups showed a return to global methylation levels comparable to the early-fasting animals, suggesting a transient decrease in transcription activity during the fasting period. We are in the process of identifying changes in specific genes involved in growth, hypoxia tolerance, and metabolism by analyzing the methylation status of CpG islands in putative promoter region sequences. Our initial results suggest that DNA methylation is an important regulator of transcription and gene expression during natural, prolonged food deprivation.