What might prompt an immediate hair-flicking response even if the spider has been still for days?

Answer

A sudden tap on the enclosure or a passing shadow

Their active defense mechanism can be triggered by sudden disturbances, such as a tap on the enclosure or a shadow passing overhead, even if the spider has appeared static.

What might prompt an immediate hair-flicking response even if the spider has been still for days?
spidertarantulapettemperamentMexican fireleg