Known as new world tarantulas in the North Americas, but called Baboon Spiders or old world tarantulas in Africa and the rest of the world, these very large arachnids belong to the family Theraphosidae. Around 900 species of these hairy spiders have been documented, of which 42 species are found in South Africa. The most commonly found baboon spiders in this country are the common baboon spider (Harpactira), the lesser baboon spider (Harpactirella), and the horned baboon spider (Ceratogyrus).
The last two segments of this spiders’ leg resembles the finger of a baboon hence the name baboon spider. Therosaphids are easily recognizable, being large, robust and hairy. The South African species range in size from 13 – 90 mm and come in hues of brown, grey, yellow or black. Their size pales in comparison to the largest tarantula in the world, the Goliath Birdeater. This enormous species which is found in South America, has been documented at a weight of around 150 grams (5 ounces), and with a leg span of up to 30 centimeters (12 inches).
The Southern African baboon spiders are largely terrestrial and are found in a variety of habitats such as dry acacia scrubland, grassland or savanna woodland. They have powerful jaws and fangs which can loosen soil and excavate burrows. In arid regions their burrows are usually deep to provide the spiders with protection from high temperatures. The burrows are lined with silk, which forms the dual purpose of both stabilising the walls, and facilitate climbing in and out.
Tarantulas have some fascinating body structures. Like most spiders they have spinnerets on their bodies that are able to spin silk. What is unusual though, is the relatively recent discovery that some tarantulas have silk producing “spigots” on their feet. Another interesting feature in North and South American species, is the presence of barbed hairs on their abdomens which the spiders “throw” as a means of defence. These hairs will irritate the noses of animals which sniff the spiders. Baboon spider species in the rest of the world are not equipped with these hairs, so over-curious animals will more likely be attacked and bitten.
In general baboon spiders are not aggressive and will only react if provoked. In South Africa the Harpactirella lightfooti from the western Cape is the only baboon spider with the reputation for being venomous. Although none of the tarantulas have venom which is deadly to humans, the old-word species venom is more potent than the new world species. Their bite, however, is extremely painful.
Baboon spiders are largely ambush hunters, preying on a variety of insects, beetles, scorpions and even small reptiles. They are also heavily preyed upon. Theraphosids of all stages are a food source for birds, centipedes, reptiles (lizards, chameleons), insectivorous mammals (honey badgers, shrews, bats, mice and baboons,) and even other arachnids such as scorpions.
Tarantulas are very long-lived spiders, (some species may take up to a decade just to reach maturity), with the males typically living a much shorter life than the females. Females have been documented to live over 30 years. When males reach maturity they leave their burrows and go in search of females with which to mate. Seeing one outside its hole could be a good indication of a male looking for females. Female tarantulas are hesitant to leave the safety of their burrows and the males have a variety of display techniques to convince them to emerge. Females will lay 30 to 180 eggs but very few spiderlings in a batch survive. Not all spiderling species can move directly after hatching, leaving these mothers with the job of protecting their young for some time.
There has been quite a decline in the number of baboon spiders, partly because of their desirability as pets. Along with the IUCN which has classified them as Commercially Threatened, three species within South Africa are designated Protected Invertebrate Animals. This restriction prohibits the collection or keeping of these creatures without a permit.