Moreover, recent studies have revealed that at least 5 species from North America- Hylachrysoscelis (Schmid 1986, Costanzo et al.1992b), Hyla versicolor (Schmid 1982), Pseudacris crucifer (Schmid 1982), Pseudacris tl-iserjata (Storey & Storey 1987), and Rana sylvatica (Schmid 1982) - survive freezing of their internal body fluids to temperatures as low as -8°C in winter.