Keep an eye on this mod

Primal adds a small, curated, and high quality selection of real world animals into Minecraft. It boasts impressive visuals, logical gameplay, as well as good variety across all biomes.

When it comes to enhancing the feel of the world, Primal does a fantastic job at making the ecosystem feel more alive. Alongside the new mobs, it also tweaks a few animals from the game such as the rabbit and dolphin, such that vanilla animals do not feel out of place.

Unfortunately, the mod lacks a good amount of content. Not to say that it isn't worth your time, it almost certainly is for those who want to spruce up their world with fauna, but there isn't much to do with the fauna. Each creature has one or two usually mundane features.

If I had to compare it to Alex's Mobs, what I would consider its competitor, I would say Alex's mobs takes quantity of content, but Primal has much higher quality under its belt.