Leatherback sea turtle shallower water at night (when the jellyfish rise up the water column). This hunting strategy often places turtles in very frigid waters. One individual was found actively hunting in waters that had a surface temperature of 0.4 °C. (32.72 °F). Leatherback turtles are known to pursue prey deeper than 1000 m—beyond the physiological limits of all other diving tetrapods except for beaked whales and sperm whales. Their favored breeding beaches are mainland sites facing the deep water, and they seem to avoid those sites protected by coral reefs. Adult "D. coriacea" turtles subsist almost entirely on jellyfish. Due to their
Varieties of Chinese increase, although there are also some sharp boundaries. However, the rate of change in mutual intelligibility varies immensely depending on region. For example, the varieties of Mandarin spoken in all three northeastern Chinese provinces are mutually intelligible, but in the province of Fujian, where Min varieties predominate, the speech of neighbouring counties or even villages may be mutually unintelligible. Classifications of Chinese varieties in the late 19th century and early 20th century were based on impressionistic criteria. They often followed river systems, which were historically the main routes of migration and communication in southern China. The first scientific classifications, based