Adaptation to low body temperature influences pulmonary surfactant composition thereby increasing fluidity while maintaining appropriately ordered membrane structure and surface activity

► Hibernation in ground squirrels increases monounsaturated surfactant phospholipids. ► These surfactant membranes have lower phase transition temperatures and enthalpy. ► However, they maintain similar ordered phase characteristics at low temperatures. ► Unlike porcine, both squirrel surfactants function well between 3 and 37 °C. ► This thermal flexibility enables a balance between dynamic behaviour and stability.