What is normal?
Rear Horned Baboons are fossorial, so long periods underground, closed burrow entrances and heavy excavation are normal for Ceratogyrus darlingi.
Do not judge Ceratogyrus darlingi by how visible the spider is on a particular day. A secure retreat is part of good husbandry even if it means you see a Rear Horned Baboon less often.
Why tarantulas hide
Rear Horned Baboons may retreat after rehousing, before a moult, after a heavy meal or simply because the enclosure gives them a secure place to settle. Hiding alone does not mean Ceratogyrus darlingi is unwell.
If water, temperature and enclosure conditions are suitable, leave a hidden Rear Horned Baboon alone instead of repeatedly lifting cork or opening a burrow.
Burrowing
If Ceratogyrus darlingi starts digging, let the spider decide how deep or elaborate the retreat becomes. Stable substrate and securely placed decor are more useful than trying to keep the burrow visible.
A Rear Horned Baboon may move large amounts of substrate, block one entrance and open another. That is normal enclosure modification, not a reason to rebuild the setup.
Webbing
Webbing can help Ceratogyrus darlingi line a retreat, detect movement and secure the area around a burrow or cork hide. The amount varies greatly between individuals and life stages.
Do not remove established webbing from a Rear Horned Baboon just because it looks untidy. Clear only what genuinely blocks water access, a door or necessary maintenance.
Closed retreats and premoult
A sealed retreat can be a premoult sign in Ceratogyrus darlingi, but spiders also close themselves in for other reasons. Remove loose live prey, keep water available and give the spider time.
Never dig out a Rear Horned Baboon merely because it has been hidden longer than expected. Compare the behaviour with the spider's normal pattern and the condition of the enclosure.
When to investigate
Check more closely if Ceratogyrus darlingi shows several concerning changes together, such as obvious loss of body condition, inability to move normally or an enclosure problem that could prevent access to water.
Visibility by itself is a poor health measure for Rear Horned Baboons. A spider that is hidden in a secure retreat may simply be behaving exactly as the species or individual prefers.