4 And it came to pass that as many as did believe him did go forth to a place which was called Mormon, having received its name from the king, being in the borders of the land having been infested, by times or at seasons, by wild beasts.
5 Now, there was in Mormon a fountain of pure water, and Alma resorted thither, there being near the water a thicket of small trees, where he did hide himself in the daytime from the searches of the king.
So Alma’s in hiding from King Noah, at a fountain (or spring) near a thicket of small trees. Interesting the “small” detail. This says the trees are small, not the thicket.
It’s in a place that is “infested” by wild beasts during certain seasons. Webster’s says “beasts” is “usually applied to large animals.” So perhaps its on a migration route of some larger animals that come in enough numbers to overwhelm the area (or at least the observer).
If the BoM happened in North America (big “if”, the verdict is still very much out), this could certainly refer to the American buffalo or bison. The Encyclopedia Britannica says they migrated north-south. An article from the University of Nebraska says the encyclopedia is wrong. Interestingly though, it does mention:
In Canada, bison sometimes moved from the plains into the bordering aspen parklands during severe winter weather….”
Aspen are smaller than many evergreens in North America, and commonly grow in groves. I can’t think of any large animal in North or Central America that “infests” a place like the bison once did. Their herds were huge.
So one distinct possibility was that he was in an aspen grove near a spring, and that huge herds of Bison would migrate nearby, perhaps taking shelter in the grove during winter. There’s nothing conclusive in the text, but it’s a possible candidate that came to mind, when I stopped to think about and research (a little) the details that are provided in Mormon’s account.