King Julien is a ringtailed lemur. Madagascar's primary mammal fauna are lemurs, and there are many different species of lemur on the island.
As the self-proclaimed "Lord of the Lemurs", King Ringtail Julien XIII ruled over a great colony of lemurs in Madagascar with charisma and certainly little ability to lead. It's a goof for Julien to be a king since male ring tails are not leaders (although in the movie Maurice said he was "self-proclaimed" lord of the lemurs). Julien had parties for his people on Madagascar with much frequency, the likes of which were interrupted constantly by the Fossa, which trespassed onto the lemur villages, interrupting their parties, ripping their limbs off, stealing their women and devouring all that they could catch. 
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