The animal on the cover of Data Structures and Algorithms Using JavaScript is an Amur hedgehog (Erinaceus amurensis), also known as the Chinese hedgehog. This species is 1 out of 14 that can be found worldwide today, and is native to Amur Krai and Primorye in Russia, Manchuria in China, and the Korean Peninsula. Like most hedgehogs, the Chinese hedgehog prefers tall grasses and undergrowth. In the wild, they feed on worms, centipedges, insects, mice, snails, frogs, and snakes. Named for the distinct noise made as they forage for food, they hunt primarily using their senses of smell and hearing. Their sniff often resembles a pig-like grunt.
The Amur hedgehog weighs an average of 1.3 to 2.2 pounds and measures between 5.5 to 12 inches in length, its tail measuring around 1-2 of those inches. As a deterrent to predators (such as birds or wild dogs), the hedgehogs are covered in short, smooth spines. If threatened, the hedgehog rolls up into a ball, leaving only the spines exposed; this is also the position in which the hedgehog sleeps, usually in cool dark depressions or holes.
Hedgehogs are solitary animals, not often socializing with other hedgehogs even when encountered while out foraging for food. The only time hedgehogs socialize is during mating season, after which they go their separate ways, leaving the female hedgehog to raise any young that were conceived. Females are very protective of their young; male hedgehogs have been known to eat their young.