This Baby Turtle Freezes Solid All Winter
The impossible claim The baby painted turtle hatches in autumn, stays in its frozen nest all winter — up to about half its body water turning to ice briefly — and walks out in spring unharmed. The verified facts The painted turtle hatchling (Chrysemys picta) survives a winter buried in frozen soil using two different tricks: It stays put: northern hatchlings commonly hatch in autumn and overwinter in the nest — up to roughly 9 months underground before emerging in spring (Ultsch 2001; COSEWIC 2012) True freeze tolerance: rare among vertebrates — ice forms OUTSIDE its cells while cell interiors stay liquid; in a lab trial at −4°C, about 53% of total body water froze and the hatchlings recovered on thawing (Storey et al. 1988; Costanzo et al. 1998) Plus supercooling: under clean, dry conditions it can stay liquid below its normal freezing point — reported down to about −15°C in laboratory studies (Costanzo et al. 2000) Modest cryoprotectants: unlike wood frogs, no massive glucose flood — freezing triggers modest glucose (2–3x) and glycerol (~3x) increases (Storey et al. 1988) Its shell is a chemical shield: without oxygen circulation, muscles burn sugar anaerobically and lactate builds up — calcium and magnesium carbonates from the shell dissolve and buffer the acid (Dinkelacker et al. 2005) Timing matters: mortality rises sharply below about −4°C sustained; snow insulation and nest depth tip the balance (Costanzo et al. 2000; Nagle et al. 2000) Come spring (March–May), it digs out and walks to water — no medical bill. ...