Start with the enclosure
Check the basics for Psalmopoeus reduncus: fresh water, suitable moisture, a secure retreat, good ventilation and a practical temperature range of 22–27°C. A clear husbandry problem matters more than a single evening of unusual activity.
For Costa Rican Orange Mouths, maintain moderate moisture with strong ventilation and a water dish. If the enclosure is obviously too wet, too dry or difficult for the spider to use normally, correct that issue before looking for a more complicated explanation.
Know what is normal
For Psalmopoeus reduncus, Costa Rican Orange Mouths are arboreal tarantulas, so normal retreat use should make sense for that lifestyle. A hidden spider is not automatically a stressed spider, and a visible one is not automatically comfortable.
With Psalmopoeus reduncus, changes from the individual's usual routine are more informative than a generic list of 'stress signs'. Compare activity, feeding and retreat use with what the same spider normally does.
Climbing, pacing and restlessness
If a Costa Rican Orange Mouth repeatedly climbs or paces, check enclosure shape, moisture and recent disturbance. Mature males of Psalmopoeus reduncus may also roam much more after the ultimate moult.
One short burst of activity from Psalmopoeus reduncus matters less than a persistent pattern combined with poor body condition or an obvious enclosure problem.
Feeding changes
With Psalmopoeus reduncus, food refusal in Costa Rican Orange Mouths is often normal around premoult, after a heavy meal or following a rehouse. Keep water available and remove ignored live prey.
If Psalmopoeus reduncus stops eating but remains well hydrated and otherwise behaves normally, observation is usually more useful than repeatedly opening the enclosure and offering food.
Changes that need quicker attention
In Psalmopoeus reduncus, visible injury, haemolymph loss, severe dehydration, inability to stand normally or major loss of coordination in a Costa Rican Orange Mouth deserves prompt attention.
If Psalmopoeus reduncus is physically deteriorating, correct any obvious husbandry problem immediately and seek experienced or veterinary help where appropriate.