where individuals choose mates and engage in copulation. Alligators may also bellow to publicize their size, a behavior which occurs in multiple other vertebrates. The size of a specimen is a significant factor for mating; females only mate with males larger than themselves. Bellowing is most common at 6:00–7:00 am and 11:00–12:00 am CST. Although these bellows occur most frequently during the mating season, adults also bellow throughout the rest of the year. Young Chinese alligators often communicate with each other and their parents using vocal signals to "maintain group cohesion". Young also make sounds when in danger, which alert adults to help and caution nearby young of the threat. Embryos produce distinctive sounds inside their eggs, which alert the adult female that the nest is ready to be opened. These vocalizations are high-pitched, while their danger calls are louder. Distribution and population The range of the Chinese alligator is extremely restricted; as of 2015, the only places it is confirmed to live in the wild are Xuancheng, Nanling County, Jing County, Wuhu, Langxi County, and Guangde County – six counties and cities in the province of Anhui, occupying a total area of about . It has been reported to rarely occur in the provinces of Jiangsu and Zhejiang, but it is unknown whether it still lives there. It is the only species in the family Alligatoridae that lives on a continent other than North or South America. Habitat The habitat of the Chinese alligator is bodies of fresh water, particularly wetlands and ponds, in areas transitioning between subtropical and temperate climates. It lives at the base of mountains, in areas where grass and shrubs are common. Habitat loss has also forced it to live at higher elevations than it prefers, where the weather is colder and the soil is unfit for burrow digging. Crocodilian conservationist John Thorbjarnarson observed a female who had to build her nest of pine needles rather than the usual plants; the eggs died due to the pine needles not being able to warm them properly. Population and range trend The oldest record of the Chinese alligator is a skeleton fragment found in western Japan. The fossil is estimated to be from the late Pliocene period, 3 million years ago (Mya). The skeleton showed that the species was larger at the time than it is currently, with a total length of at least . Alligators are