Theraphosa stirmi, also known as the Burgandy Goliath Bird Eater, is endemic to Guyana, Brazil, and is one of the largest spider species in the world by size and girth. This colossal beast has the potential to reach a diagonal leg span over 25 cm (10 in). Adult and subadult specimens have a rather dull brown coloration throughout the body and are often characterized by the absence of long hairs on the patella and tibia. Unique amongst female specimens is a distinct row of short and strong spines along the skin of the apical femur of leg IV. Male specimens have a loss of tibial apophysis and a prolateral superior bulbal keel extension towards the distal tip. As slings and juveniles, their coloration is also rather dull with a grey and brown color covering most of the body but recognized by the bright white coloration on the tarsi and metatarsi on legs I and II combined with the bright dense bristles covering the entire body. Theraphosa stirmi can stridulate with stridulatory setae located between the palps and Leg I and between Leg I and II.

Natural environment

Guyana is located on the northern coast of South America alongside Venezuela to the west, Suriname to the east, and bordered by the Atlantic Ocean to the north. Throughout Guyana, the land consists of a vast change of natural regions with marshy plains along the coast, sand belts, and hills further inland, dense rainforests to the south, and dry savannah regions to the southwest. This part of South America, especially Guyana, and the surrounding regions, obtains one the highest levels of biodiversity i.e. genetic variety in the world within both fauna and flora with thousands of endemic species. The country holds one of the largest rainforests in South America with over 80% covering the land and a large part of the rainforests are unspoiled and inaccessible to humans.

The climate of Guyana is tropical, humid, and hot with two rainy seasons that take place from May to August and November to January with an annual rainfall of 1500 to 2000 mm or 60 to 80 in. However, the hot and humid environment is often reduced due to the Atlantic Ocean with northeast trade winds reducing the temperature and humidity along the coast and a bit further inland, with temperatures ranging between 16°C and 34°C (60°F to 93°F). This tropical climate and unique environment alongside rich rainy forests have created multiple ecosystems with high levels of endemism, meaning that species are found nowhere else but within defined geographical areas.

Behavior

Theraphosa stirmi is an opportunistic burrower as wild specimens have been observed in long tubelike burrows. However, if the opportunity arrives the spider will overtake pre-dug burrows from other animals such as rodents. The species is often found close to rivers or other streams.

Younger specimens tend to burrow more compared with subadults and adults. This species is not a heavy silk spinner, close to nothing for the visible eye. When threatened the spider is prone to kick hairs, but with age, this behavior is often reduced and the overall behavior becomes less defensive. If they feel threatened, larger specimens often stridulate which is another defensive mechanism that generates a “hissing” sound to warn off predators.

Being a new world species, they can kick urticating hairs, type III, as the primary defense rather than biting. The venom from this species is not classified as medically significant and can be compared to a yellowjacket sting. However, if bitten and envenomated the side effects are often local swelling and nausea.

Enclosure/Terrarium

Terrarium: The ideal enclosure size for an adult specimen is a minimum of 60x40x30 cm or 24x15x12”, to provide the necessary surface area for such a large species. Younger specimens should also be kept in enclosures that provide enough surface area so the spider can move rather freely with the opportunity to burrow.

Substrate: Being an opportunistic burrower they should be given a substrate depth of minimum 10 cm (4 in). To achieve the perfect conditions for the spider it is recommended to use either tree trunks or similar structures embedded in the substrate to guide and help the spider with its burrow furthermore giving a good esthetic look. Providing a dark and snug hide is essential for their wellbeing. I use both tree trunks and cork bark which works perfectly. To raise the esthetic look as well as encourage the spider to be more visible, add dead leaves and other natural materials such as bark to create a natural forest landscape. The substrate should never be soggy but instead wet/moist. I use a mixture of cocofiber, sand, and sphagnum moss which will help retain moisture in the substrate.

Plants: Using plants is recommended, either plastic or preferably real due to their ability to hold moisture. Providing plants does increase the likelihood for the spider to be outside its burrow more frequently. By creating a canopy-like environment the spider will eventually feel less threatened and safe outside the burrow. For my Theraphosa stirmi, I use epipremnum aureum, pachira aquatica and natural mosses.