I asked my research friend about what activity "her monkeys"
have and got the following reply:

"We have mostly rhesus monkeys, but also some cynomolgus and
a very few titi monkeys.  There are a few noctural
pro-simians, but they are not the one we have  at the
center.  The species we have are not active at night.  They
pretty much stay put.  They tend to bed down with their
maternal family groups... which is also what their  social
structure is based on.  They know who their moms are, but
not their dads.  Over the past 5 years they've done DNA on
most of the field corrals (1/3 acre cages where many animals
from many family groups are housed) and there have been some
surprises about the sires.  The dominant ones are not always
the ones breeding."

So we can say for sure that those primates go to bed at dark
:)
--
   Elisi Tsayonah, AniWodi, ghigau,
   St Francis River Band of Cherokee