What should I use to make my boards and why or does it not matter. Seems most commercial boards are bass wood, wondering if there is a reason other than being soft wood.

Soft Is the main reason. Easy to put In your push pins or If your using staples.

Friend of mine told me Cedar is nice to work with, as its soft wood i`ve built all mine out of pine, as cedar is little more money, and i`m a cheap bugger. ha ha.
The pine boards work well, just find its a little harder to push the pins into it, thats all.
My two cents.

Cedar shakes are great for smaller boards especially muskrat, weasel and squirrel. Pine for your larger boards is fine.

I make my boards from cedar fence pickets.

Cedar here also.
Pine for bigger boards.

Bass wood all the way. I would hate to have to pull staples out of pine. Or push push pins In that pine. Cedar would probably work but bass wood Is so much cheaper.

The pine I got is softer than the cedar.

I made all mine out of free pine. The answer to your question is no, there is no other reason. Pine works just fine and even better when it's free. I will say try to place any knots in an area where you won't have to pin.

Ive made mine mainly out of basswood for the ease to work with. My older ones were made from plywood. These took to long to sand so I wouldn't get slivers in the hides. Basswood if you can get it. IMO

boco, does the pine and cedar harden over time?

Not that I noticed,but strike x is right about the knots on the pine.I also make sure there are no knots on any edges.Also have to discard any boards with pitch pockets.
Basswood is nice,but we don't have any around here,and poplar warps bad.

If your using staples you sure don't want to be using pine. It's way to tough when It comes to removing them.
If your a coon trapper staples and wire mesh for the tails are the trappers best friend.

My favorite wood for pelt boards is Western Red Cedar. It is soft to put push pins in and has a natural oil which allows pelts to be removed easily. They last forever. Just gave away at our Local raffle some more of my boards from the 70's with still lots of use left in them yet. Some of my new boards I have been making. The marten boards are also tapered on the flat side from back of the board to the nose.

I got to looking at 1x8 Whitewood boards the other day at the local Hardware Store (reasonable price). I asked the manager what exactly Whitewood is.....he said its a Canadian Spruce Fir that is softer than the yellow pine and often used in cabinetry. Do you all think this Whitewood would work for some Otter Boards?

Go for It.
But the only problem I can see Is that wood Is going to be 3/4 of a inch thick. And In my opinion that's to thick for a wood form.

Buddy has a big planer at his house. Figured I could watch it eat while kicking back a few cold ones. Gonna give the whitewood a try.

I got lucky, a friend gave me a bunch of basswood...

Not sure what Canadian Spruce Fir is. It would have to be either spruce or fir, two entirely different species. Lumber is marketed as SPF which is Spruce Pine Fir. Not a single species but a mixture of those species. I have a few boards from clear spruce and pine but they are very hard to push your push pins into. Fir would be even harder.

Along with western red cedar, basswood is an excellent choice for pelt boards.

Thanks Ron....It must be the SPF your talking about.