a variety of objects, often logs, but have even been seen basking on top of common loons that were covering eggs. The turtle starts its day at sunrise, emerging from the water to bask for several hours. Warmed for activity, it returns to the water to forage. After becoming chilled, the turtle re-emerges for one to two more cycles of basking and feeding. At night, the turtle drops to the bottom of its water body or perches on an underwater object and sleeps. To be active, the turtle must maintain an internal body temperature between . When fighting infection, it manipulates its temperature up to 5 °C (8 °F) higher than normal. Seasonal routine and hibernation In the spring, when the water reaches , the turtle begins actively foraging. However, if the water temperature exceeds , the turtle will not feed. In fall, the turtle stops foraging when temperatures drop below the spring set-point. During the winter, the turtle hibernates. In the north, the inactive season may be as long as from October to March, while the southernmost populations may not hibernate at all. While hibernating, the body temperature of the painted turtle averages . Periods of warm weather bring the turtle out of hibernation, and even in the north, individuals have been seen basking in February. The painted turtle hibernates by burying itself, either on the bottom of a body of water, near water in the shore-bank or the burrow of a muskrat, or in woods or pastures. When hibernating underwater, the turtle prefers shallow depths, no more than . Within the mud, it may dig down an additional . In this state, the turtle does not breathe, although if surroundings allow, it may get some oxygen through its skin. The species is one of the best-studied vertebrates able to survive long periods without oxygen. Adaptations of its blood chemistry, brain, heart, and particularly its shell allow the turtle to survive extreme lactic acid buildup while oxygen-deprived. Anoxia tolerance During the winter months, painted turtles become ice-locked and spend their time in either hypoxic (low oxygen) or anoxic (no oxygen) regions of the pond or lake. Painted turtles essentially hold their breath until the following spring when the ice melts. As a result, painted turtles rely on anaerobic respiration, which leads to the production of lactic acid. However, painted turtles can tolerate long periods of anoxia due to three