The ability to perform prolonged apnea (breath hold) is a key adaptation in diving mammals. Pinnipeds (e.g., seals and sea lions) are known to practice apnea on land, and the ability to extend breath hold duration tends to increase with ontogeny. In this study, we describe the development of apneustic breathing in the Weddell seal (Leptonychotes weddellii), a deep-diving species, throughout the dependence period. We hypothesized that both age and early experience in the water would influence the development of apneustic breathing in this species. To test this, we characterized the respiratory patterns of known-age Weddell seal pups (n=19) using video footage of pups hauled out of the water and resting on ice, every 1-2 weeks from 1 week through 7 weeks of age. We quantified eupneic (i.e., normal) respiration rate (breaths/min), presence/absence of apneustic breathing, and apneustic interval (length of breath hold) for each recording. We found that most animals did not perform apnea until after their first entry into the water, and that apneustic interval was significantly positively correlated with age (r²=0.245, P=0.0012). These results are consistent with early developmental patterns in other pinnipeds, and further, this is the first study to correlate physiological development with early behavioral experience in the water. Future work will correlate apneustic interval with dive depth and duration for a subset of pups (n=9) from the current study.