Sulawesi black Macaque or Latin name is Macaca Nigra also one endemic in North Sulawesi.
the red bottoms become one nickname.
it can be viewed from the female monkeys, when they were estrus.
color will look shiny red ass when it was swollen maximum.
so when they would estrus, their butt will swell day by day.
up to the maximum swelling and that’s when the alpha male will follow the female.
because when the female is in estrus peaks, that the time is right for alpha males mating.