The giant cave huntsman spider (Heteropoda maxima) is the largest spider by legspan in the world — and one of the more startling encounters available to visitors inside Niah's caves. Adults of this species reach a legspan of 25–30 cm, with a body the size of a large man's palm. They are flat-bodied spiders that press flush against cave walls and ceilings, making them difficult to spot until they move. When they do move, it is fast — a sudden sprint across several metres of ceiling in pursuit of a cave cricket or other prey.
Huntsman spiders are not web builders. They hunt actively by sight and touch, running down prey rather than trapping it. In total darkness, the cave huntsman relies primarily on vibration — its legs are covered in highly sensitive hair receptors that detect the footsteps of a cricket through solid rock. An experiment in artificial darkness showed that the spiders are completely competent hunters even when blinded. Their venom is fast-acting for insects but poses no serious risk to humans — the bite is described as painful and causing local swelling, similar to a bee sting.
Despite their appearance, giant cave huntsmen are not aggressive toward humans. Approaches to within a metre typically elicit a repositioning movement rather than a threat display. The spiders are most visible in the dim transitional zones between the lit and fully dark sections of the Great Cave — look up at the ceiling as you cross the threshold from daylight to darkness. In the deeper sections, shine a torch sideways along the cave ceiling rather than directly: this angle catches the eyeshine of multiple spiders simultaneously.
The giant huntsman was formally described by German arachnologist Peter Jäger in 2001 from specimens collected in Laotian caves but is known from cave systems across Borneo including Niah. It represents one of the most specialised predators in the cave ecosystem — a surface-adapted hunter that has colonised the cave environment so successfully it has become its apex invertebrate predator. After the cave experience, the boardwalk back through the rainforest offers a pleasant decompression before returning to the park accommodation.