If your on mobile and can’t find one of these guys start the tame equus pursuit and walk or fly around the island and eventually a arrow will show up on the top left of your screen. If you follow that then you will find an equus or two. Upvoote if you found this helpful.
Put this higher !!So if you play mobile I found 3 in the same spot okay so first do the volcano pursuit the one where it's the cave inside the pursuit should be south of the equator and in that general area if you look around you'll find them
If hard to find on The Island, a herd seem to spawn near the red obelisk, green obelisk and the black sand area off the river next to the redwoods, I killed a bunch of low levels for some easy pelt and I came back after 10-15 minutes, after I found a 145 Equus. Hopefully you found this helpful.