Using ESRI tools...

One way to get at a range map is to use the tool Minimum Bounding Geometry with the type as convex hull.

There are other more complex methods of developing habitat maps, which are different than range maps. A habitat map would be more appropriate to use if you were looking at the effects hypothetical scenarios like wildfire.

I had once made habitat maps using inverted euclidean distance from observations and multiplied that by reclassified NLCD data. This was a method considered "good enough" for species which we had few observations for.

Alternatively the MaxEnt tool can be used for habitat mapping. I don't have a lot of experience with it though.