Unlike most arachnids, amblypygids have a well-developed olfactory system between the anatomy of their whips and the arrangement of their nervous system (Hebets, 2002). Studies have shown they can detect and respond to a wide variety of volatile chemicals found in their environment, similar in range to many insects (Hebets & Chapman, 2000, A). While amblypygids possess 8 eyes on their prosoma, they lack a tapetum, the light-reflecting layer used for night vision in some spiders. This makes their eyes virtually useless in their nearly pitch-black natural habitats, so they mostly rely on olfaction and mechanoreception (Hebets, 2002). Amblypygids usually walk sideways, like crabs, waving their antenniform legs in front of them as they go. (Levi et al., 1968).
Male phrynids have been observed wandering more than their relatively sedentary female counterparts, likely searching for mates. This observation likely applies to all amblypygid families (Fowler-Finn & Hebets, 2006).
Amblypygids may fight same-sex members of their species to decide competitions over resources, territories, and possibly mates. In phrynids, a study on agonistic interactions (on Phrynus marginemaculatus) showed that male-male contests consists primarily of rapid flicking of the whips combined with pedipalp displays. If a victor isn’t decided from such displays, these “battles” can sometimes escalate into the combatants contacting each other’s pedipalps and elevating their bodies off the ground, using their open pedipalps to push away from each other. Whichever individual remains elevated the longest typically wins, with the loser retreating uninjured. Females will fight each other similarly, but fight more shorter periods and are more likely to escalate to the contact phase. This may be because wandering males are more likely to come into contact with each other than females, leading to the sexually dimorphic evolution of a more ritualized fighting behavior. Because both males and females exhibit this behavior, it is likely that the battles are not primarily over mate choice. (Fowler Finn & Hebets, 2006)
At least some phrynids have the ability to survive for extended periods underwater, a useful adaptation for small animals in flood-prone areas. A study on Phrynus marginemaculatus showed that when submerged, the amblypygid could perform plastron respiration to take in enough oxygen from the surrounding water to survive without negative consequences for over 24 hours. Plastron respiration is the ability of some arthropods to maintain a bubble of air around their cuticle using surface tension. Ambient oxygen can diffuse through the bubble, allowing the arthropod to survive underwater. Phrynus marginemaculatus is the first known animal without a tracheal respiratory system (like most arachnids, amblypygids possess book lungs) to perform plastron respiration. (Hebets & Chapman, 2000, B)
Observations at Barro Colorado Island in Panama have shown that Phrynus gervaisii individuals are found more commonly than expected by chance in front of active colonies of Paroponera clavata, the bullet ant. The whip spiders are ignored by the predatory ants, even when they go into a craze defending their nest, and the whip spiders in turn make way for the ants as they enter and leave the nest. This suggests that at least some phrynids have developed an inquiline relationship with the bullet ant, wherein setting its territory near an ant colony protects the whip spider from diurnal predation (how this might serve the ants is unknown) (LeClere et al., 1987).