New players have a randomly selected default character skin of either Steve or Alex, but the option to create custom skins was made available in 2010. Players encounter various non-player characters known as mobs, such as animals, villagers, and hostile creatures. Passive mobs, such as cows, pigs, and chickens, can be hunted for food and crafting materials. They spawn in the daytime, while hostile mobs—including large spiders, skeletons, and zombies—spawn during nighttime or in dark places such as caves. Some hostile mobs, such as zombies, skeletons and drowned (underwater versions of zombies), burn under the sun if they have no headgear. Other creatures unique to Minecraft include the creeper (an exploding creature that sneaks up on the player) and the enderman (a creature with the ability to teleport, pick up, and place blocks). There are also variants of mobs that spawn in different conditions; for example, zombies have husk variants that spawn in deserts.