Tarantulas are slow and deliberate movers, but accomplished nocturnal predators. Insects are their main prey, but they also target bigger game, including frogs, toads, and mice. The South American bird-eating spider, as it name suggests, is even able to prey upon small birds.

A tarantula doesn't use a web to ensnare prey, though it may spin a trip wire to signal an alert when something approaches its burrow. These spiders grab with their appendages, inject paralyzing venom, and dispatch their unfortunate victims with their fangs. They also secrete digestive enzymes to liquefy their victims' bodies so that they can suck them up through their straw-like mouth openings. After a large meal, the tarantula may not need to eat for a month.

Tarantulas have few natural enemies, but parasitic pepsis wasps are a formidable exception. Such a wasp will paralyze a tarantula with its sting and lay its eggs on the spider's body. When the eggs hatch, wasp larvae gorge themselves on the still living tarantula.

The tarantula's own mating ritual begins when the male spins a web and deposits sperm on its surface. He copulates by using his pedipalps (short, leglike appendages located near the mouth) and then scuttles away if he can—females sometimes eat their mates.

Females seal both eggs and sperm in a cocoon and guard it for six to nine weeks, when some 500 to 1,000 tarantulas hatch.