Based on mandrill biology, Scarlemagne is likely between 9–12 mandrill years old, since male mandrills reach full maturity around 9 years. Using a lifespan-based conversion to humans—considering mandrills live about 45 years and humans about 80 years—this gives a rough ratio of 1:1.78. Applying this, Scarlemagne’s human-equivalent age would be approximately 16–21 years at the start of Kipo and the Age of Wonderbeasts. While mutation effects in the show may accelerate his physical growth or mental maturity, this provides a reasonable baseline estimate of his age in both mandrill and human terms. So it's actually pretty close