Finding this animal can be extremely difficult especially on official servers if you don't have a flyer yet. It's less rare near mountains and metal spawns. One of the most easy places to find one on the Island, is in the middle of redwood.
For some reason on the island, there is always one lonely doedic at the edge of the forest(not redwoods) and the snow biome. I feel so bad for it because the only other dinos are sabers, scorpions, argies, raptors, rexes, and allos( all which try to eat it at the same time)