True tarantulas are spiders belonging to the family Theraphosidae. Certain members may also be known as bird spiders, monkey spiders, baboon spiders or rain spiders. They are characterized by having tarsi (feet) with two claws and claw tufts, called scopulae. Related families include the funnel-web spiders and the trap door spiders, which sometimes are also called tarantulas. The family Theraphosidae includes over 800 different species of tarantulas, divided over 12 subfamilies (formerly 13) and 113 genera. Tarantulas are nocturnal predators, killing their prey by injecting venom through their fangs. The hungry tarantula typically waits partially hidden at the entrance to its retreat to ambush passing prey. It has sensitive hairs that enable it to detect the size and location of potential victims from the vibrations caused by their movements. Some species also use their silk fiber to detect motion (when prey triggers a line). Like many other spiders, it cannot see much more than light, darkness, and movement, and uses its sense of touch to perceive the world around it. That being said, they are anything but sloppy or imprecise about the way they capture their prey. They generally seem to choose prey on the basis of how dangerous it is perceived to be, the general size of the potential prey animal, etc. Some tarantulas succeed in occasionally capturing small birds, small mammals such as mice, and even small fish, but their ordinary prey consists of insects such as crickets (for ground dwellers) and moths (for arboreal species). Tarantulas usually live in solitude and all being cannibalistic, will attack and eat others of their own kind.