Tarantulas are among the most recognized terrestrial spiders, often distinguished by their large size and hairy appearance. A common point of curiosity revolves around their speed, considering their body mass and unique anatomy. Their locomotion is a complex interplay of size, physiology, and environment, resulting in variable but often rapid movement. Understanding how fast a tarantula can run requires looking closely at measurements across different species and the specialized mechanisms that power their eight legs.
Documented Speed and Species Variation
The running speed of a tarantula varies widely, largely depending on its species and natural habitat. Most tarantulas are built for short, powerful bursts of speed rather than sustained running. For example, some slower-moving, burrowing species, like the Brazilian Black tarantula, have been measured at an average speed of only about 0.3 feet per second (around 9 centimeters per second).
Other species, particularly those that actively hunt or are more arboreal, are significantly faster. The Goliath Bird Eater, despite being the largest spider on Earth, is capable of reaching speeds over three feet per second (about 91 centimeters per second) in a sprint. Scientific studies on the Texas Brown tarantula (Aphonopelma hentzi) have recorded maximal sprint speeds ranging from approximately 0.69 to 1.75 feet per second (21 to 53.2 cm/s). This variation highlights that some tarantulas possess a considerable capacity for rapid movement when necessary.
The Unique Mechanics of Tarantula Movement
Tarantulas and other spiders employ a method of movement that differs significantly from that of mammals or insects. Their legs lack the extensor muscles that most animals use to straighten their limbs. Instead, tarantulas rely on a specialized hydraulic system powered by the pressure of their internal body fluid, known as hemolymph.
Locomotion is achieved by contracting muscles within the cephalothorax, the fused head and chest section of the body. This contraction increases the internal hemolymph pressure, forcing the fluid into the legs’ joint cavities. This pressurized fluid acts as a hydraulic force to extend the two main joints in each leg—the femur-patella and the tibia-metatarsus—pushing the leg outward.
Flexor muscles are present in the legs, which work antagonistically to the hydraulic pressure, allowing the leg to bend and retract. For a tarantula to achieve a high-speed sprint, it must generate substantial internal pressure. During intense activity, the hemolymph pressure inside the body cavity can increase dramatically, sometimes reaching up to 60 to 130 kilopascals (kPa). This mechanism enables the swift, powerful extension needed for quick bursts of movement.
Biological and Environmental Factors
The performance of the tarantula’s hydraulic system is sensitive to both internal and external conditions. Temperature is one of the most significant external factors influencing speed, as tarantulas are ectotherms and rely on their environment to regulate body processes. Scientific testing shows that as the ambient temperature increases, the spider’s sprint speed also increases substantially. This is partly because warmer temperatures reduce the viscosity of the hemolymph, allowing the fluid to flow more easily and rapidly through the legs.
Internal factors, such as hydration, are also directly linked to the hydraulic system’s efficiency. A tarantula requires adequate hydration to maintain the necessary fluid volume and pressure for forceful leg extension. Dehydration can compromise this system, leading to a noticeable decrease in their maximum running speed. Furthermore, the type of substrate or terrain affects how quickly they can move. Loose, fine, or slick surfaces can hinder their traction and slow them down compared to running across rougher, more solid ground.
Tarantula size also plays a role. Larger individuals typically move slower relative to their body length compared to smaller ones. However, at the highest speeds, increased temperature can lead to reduced coordination between the joints, causing the spider’s gait to become less controlled despite the overall increase in velocity.
Locomotion Purpose: Why Speed Matters
Maximum speed in a tarantula is reserved for moments of survival, either as an attacker or an escapee. Tarantulas are ambush predators that generally wait for prey to come near their burrow or territory. When a suitable insect or small vertebrate is detected, they rely on a sudden, explosive burst of speed to close the distance and secure the prey. This rapid acceleration prevents the prey from escaping the short strike range.
The most frequent use of their top speed is predatory evasion, escaping from larger threats like birds, lizards, or the specialized tarantula hawk wasp. Rather than engaging in a fight, a tarantula will rapidly bolt to the safety of its burrow or a dense hiding spot. This short-distance sprint capability is a crucial defense mechanism against sudden danger.
Speed also plays a role in mating. After a male successfully courts a female and attempts copulation, the act must be completed quickly. The male transfers sperm using specialized appendages and must retreat immediately afterward to avoid being cannibalized by the female. The speed of his departure is often a matter of life or death.