Over time, some zoos have mimicked an animal's natural habitat. While some zoos are becoming more animal-friendly, many still lag behind. Many of the smaller zoos continue to have small concrete enclosures with little nature. When an animal is locked up in a small enclosure it is unable to satisfy its needs that nature can easily provide. Animals like elephants are used to walking 30 kilometers a day, at the zoo they cannot satisfy their needs. Needs that cannot be satisfied lead to unhealthy behaviors. According to PETA, “Many develop neurotic and self-injurious behaviors [known as] zoocosis, which are rarely, if ever, observed in the wild. Primates throw feces and eat their own vomit. Birds pluck their feathers. Tigers walk incessantly and polar bears swim endless figure eights. In the zoo animals cannot even experience hunting for their own food. Most zoo animals are predatory animals, who like to hunt for food. A zoo can't provide that; then the animals are fed in bowls. A zoo is nothing compared to the wilderness. There is no limit to where animals can walk, fly or swim. There is no concrete around, just pure nature. Animals live authentic lives in the wild while playing an important role in their ecosystem. Hunting is an exciting part of the day for some animals, while others face challenges against natural selection. In theirs