Many temperate amphibians spend up to 6 months every year at very low temperatures, during the winter. Many frog species spend the winter submerged under the ice of frozen ponds and lakes. Under these conditions, the overwintering environment becomes extremely hypoxic, often leading to the death of many of its inhabitants. At the same time, the water beneath the ice becomes stratified for temperature and oxygen, being warmer at the bottom than below the ice as well as being more hypoxic. I have shown that cold-submerged frogs can detect these oxygen and temperature gradients even during their overwintering torpor, and exhibit distinct preferences for both. If the overall oxygen level in the water falls too low, frogs will select temperatures as cold as possible to lower their metabolic requirements and alleviate the hypoxic stress. Thus, the overwintering frog provides us with some proof for the ecological relevance of hypoxia-induced hypothermia.