Seals may perform long-duration dives that leave them severely hypoxic, and thereby represent interesting mammalian models for comparative studies of hypoxia tolerance, particularly in relation to brain function. The arctic ice- breeding hooded seal (Cystophora cristata) may dive to ~1 000 m for durations of >50 minutes (Folkow & Blix 1999), an ability that is related to its high capacity to store oxygen in a large haemoglobin-rich blood volume and in skeletal muscles that carry the highest myoglobin concentration yet recorded (Burns et al. 2007). Like other seals, hooded seals also display distinct diving responses encompassing bradycardia and massive peripheral vasoconstriction that limits the distribution of oxygenated blood to all but the most hypoxia- vulnerable tissues. A diving-induced vascularly mediated body cooling causes brain temperature to drop by up to 3°C, thereby depressing metabolism as well as offering protection against hypoxic and oxidative stress (Odden et al. 1999). We have recently also found that hooded seal cortical neurons are intrinsically more hypoxia tolerant than cortical neurons of non-diving species, possibly due to enhanced anaerobic capacity, channel arrest mechanisms and effects of an unusual distribution of the neurally based respiratory protein neuroglobin. Lessons learned from studies of survival strategies in hypoxia-tolerant mammals like hooded seals may potentially help guide efforts to find effective treatments of hypoxic injury in man. Burns, J.M., Lestyk, K.C., Folkow, L.P., Hammill, M.O. & Blix, A.S. 2007. J. Comp. Physiol. B. 177, 687–700. Folkow, L.P. & Blix, A.S. 1999. Polar Biol. 22, 61–74. Odden, Å, Folkow, L.P., Caputa, M., Hotvedt, R. & Blix, A.S. 1999. Acta Physiol. Scand. 166, 77–78.