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October 2012
Contents / home
Volunteers at the zoo
Let's stop hawkers
Vital role of our oceans
Holiday fun in the sun!
On the horns of a dilemma
Walkthrough aviary to open
Cape vulture chick born
Getting flamingo nests ready
Innovative magnetic sweeper
Bear necessities
ZooClub updates
Horned baboon spider
Conservation Grapevine
 

Horned baboon spider - "primitive" spider sporting a horn

 
  Horned baboon spiders are unique due to the distinctive horn projecting out of their carapace.
 
  Baboon spiders have large black fangs that project downwards from the jaw.
 
  Horned baboon spiders construct permanent silk-lined burrows in the ground at various depths.
 
  The common name, 'baboon spider' has been derived from two conceptions - one, that the spider's last two leg segments resemble that of a baboon's finger and two, the spider's hairy appearance and black pads on their 'feet', which resemble the pads on baboon feet.
 
  Horned baboon spiders can be viewed at the NZG's Spider Room, which is situated next to the chimpanzee enclosure and across from Stormy Bay.
Horned baboon spiders (Theraphosidae ceratogyrus darlingi) are endemic to southern Africa and have a distinctive horn projecting from the top of their carapace (head). The shape of the horn varies between species.

Primitive spiders

Southern African spiders fall under two main suborders - the Araneomorphae and the Mygalomorphae. The Mygalomorphae are our more primitive spiders and include the baboon and trapdoor spiders. They are some of our largest and hairiest spiders, usually living in silk-lined burrows or retreats. The baboon spiders include several genera such as the Horned baboon spider. These spiders do not build webs and are ground dwellers.

Outside of Africa, baboon spiders are known as tarantulas and are considered the giants of the spider world. The common name, 'baboon spider' has been derived from two conceptions - one, that the spider's last two leg segments resemble that of a baboon's finger and two, the spider's hairy appearance and black pads on their 'feet', which resemble the pads on baboon feet.

Description

Baboon spider species are large, very hairy and vary in body size from 13 - 90mm (excluding their legs). They come in a variety of colours from hues of grey, brown and yellow to black. They are heavily built with robust legs and long leg-like pedipalps found near the front of the body. These pedipalps are often mistaken for legs, but are covered with hair that serves as sensory organs that they use to feel vibrations and 'taste' the ground and their prey. In males, the pedipalps have a special organ to store sperm and it is used during mating.

A cluster of eight small eyes are found on their carapace. Spiders have protruding spinnerets at the base of their abdomen from which the silk threads are pulled. Baboon spiders have large black fangs that project downwards from the jaw that can exceed 6mm in length.

Distribution and habitat

Horned baboon spiders are widely distributed throughout Limpopo and the northern parts of Mpumalanga and KwaZulu-Natal. Outside of South Africa, they can be found in Mozambique, Namibia, Botswana and Zimbabwe.

Horned baboon spiders are commonly found in dry grassland and savanna habitats and are ground dwellers that construct permanent silk-lined burrows in the ground at various depths, or in natural crevices and under rocks. Using their mouthparts (chelicerae), pedipalps and fangs, they excavate these burrows.

The entrance of the burrow is left open and has a silk rim formed from the extending silk lining that passes the entrance. This rim may sometimes include pieces of plant material that is used for concealing their burrow entrance and for prey detection felt through vibrations in the silk threads. In arid regions these spiders' burrows are found deep in the ground in order to provide them protection from high temperatures.

Behaviour

During the day these spiders rest in the deepest part of the burrow with a thin transparent silk cover over the opening; at night they come up to feed. Horned baboon spiders are predominately known to be 'sit-and-wait hunters', which entails them sitting at the burrow's entrance waiting for their prey to approach the burrow or on the soil surface nearby, where the prey is ensnared and dragged into the burrow.

Their prey includes a variety of small invertebrates such as grasshoppers, millipedes, beetles, cockroaches and even other spiders and mice. After a feed, the prey's remains are stored at the bottom of burrows as well as their exuviae, which are the remains of the spider's exoskeleton after it has moulted. When researching spiders, the exuviae of spiders can be used to determine the general aspects of a species, such as their lifecycle, sex ratio, distribution and proof of breeding in a habitat.

Reproduction

Mating typically takes place in spring and summer, with the male performing various techniques to be recognised by the female. Males have a mating spur on the front pair of legs which is used to hold the female's fangs open and to prevent her from attacking and eating him.

Courtships take place over short periods of time only. The male deposits sperm in the female's genitalia and when she lays eggs they are fertilised. She spins a waterproof silk egg sac at the bottom of the burrow in which the eggs are deposited. Horned baboon spiderlings only start becoming mobile 50 days after hatching. The juvenile spiders remain with the female spider for a period of time before dispersing, during which they undergo a number of moults, their first one being in the egg sac.

Venom

The Horned baboon spider's venom is mild and is NOT harmful to humans. However, one can be bitten by a baboon spider if they feel threatened and the bite can be painful. This can be attributed to their long, large fangs and the subsequent depth of the puncture.

Conservation

Baboon spiders are classified as 'Commercially threatened' in terms of the IUCN Red Data List on account of their popularity as pets. Horned baboon spiders are unique due to the distinctive horn projecting out of their carapace, sadly making them sought-after specimens for collectors and to be kept as pets.

In 1987, three species of the baboon spider, including the Horned baboon spider were added to Schedule VII of the Transvaal Provincial Nature Conservation Ordinance as Protected Invertebrate Animals. Today this restriction is still in place in all South African provinces. Thus, without a permit, these animals may not be collected, transported or kept.

The movie industry has portrayed baboon spiders as villainous creatures; however they are not dangerous. Even though many South African spiders possess venom, baboon spiders like the Horned baboon spider do not pose a real threat to people, even if they may look a little scary.

In conclusion, I would like to thank Dr Ansie Dippenaar-Schoeman from the ARC-Plant Protection Research Institute's Spider Research Centre in Pretoria for her help and contribution to this article.

Claire Fordred, NZG Intern


 
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Zoo and Aquarium Visitor