Even in tropical climes, fruit is seasonal.
see:
Knott, C.
"Changes in orangutan diet, caloric intake and ketones in response to fluctuating fruit availability."
Int J Primatol (1998).19: 1061-1079.
For more than half of every year these tropical apes go into ketosis due to the unavailability of fruit.
Ray Audette
NeanderThin