Jo, have you seen the herb gardens within the Sulawesi enclosure at Perth Zoo? You could possibly create a similar garden OUTSIDE, immediately adjacent to your Rhesus castle as space is such an issue inside. The top of the garden is covered with mesh and the animals can only harvest the herbs when they grow high enough for them to reach.
By the way, does that castle have a stand off barrier around it to keep the public [and Ben!] back a bit? Hard to tell from the photo and my memory is hopeless.
By the way, does that castle have a stand off barrier around it to keep the public [and Ben!] back a bit? Hard to tell from the photo and my memory is hopeless.