Loggerhead sea turtle °C (55 and 59 °F). The loggerhead takes on a floating, cold-stunned posture when temperatures drop to around 10 °C. However, younger loggerheads are more resistant to cold and do not become stunned until temperatures drop below 9 °C. The loggerheads' migration helps to prevent instances of cold-stunning. Higher water temperatures cause an increase in metabolism and heart rate. A loggerhead's body temperature increases in warmer waters more quickly than it decreases in colder water; their critical thermal maximum is currently unknown. In February 2015, a live loggerhead turtle was found floating in British Columbian waters of 10.5 °C with
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