Hi! That's awesome you've been playing with your kids. We gotta spread the MULE love!
Which version did you originally play? Atari or Commodore?
The Wampus is tough to catch. It was actually tougher to catch in the Commodore version for reasons I am 99% certain were not intended by the original developers. That being said, in regards to catching the Wampus, this version should be on par with the Atari version.
Planeteer & mule collisions with mountains, river, plot border & graphics, and town are the only cases where the shape of what species you are playing as matters, because if your planeteer overlaps a mountain (as you know) it will slow down. So, in a sense, climbing a mountain to catch the Wampus makes it more difficult.
But notice I didn't say that the shape of your planeteer colliding with the Wampus "white dot" is a factor. It's actually the case that for every mountain the Wampus visits, there is only two positions your planeteer can be at to catch it. Consider that each XY coordinate your player can *step* to is a separate position on the board. Observe the following images. The green upper left corner dot needs to be at the vertical offset from the Wampus dot as shown in the first image. And then green dot needs to be at the horizontal offset of either of the latter 2 images.
(Images courtesy of Pascal Bringer)
Notice the aspect ratio of the dots--wider than tall. That is true of the entire board. But more relevantly, is it is the ratio for the distance a planeteer moves horizontally & vertically (all throughout the game)--visually a planeteer can cover more ground moving horizontally. Another aspect is that nearly every planeteer is taller than they are wide. Why am I saying this? Consider that it takes more time to move through a mountain vertically than horizontally in most cases (and positions & mountain shapes). And back to one of my original statements, mountains slow you down.
So you want to approach the Wampus from an angle that causes the least amount of slowdown. Surprisingly although mountains certainly look very wide, I have surmised that it's easiest and most successful to wait to the side of a mountain and move in horizontally when it appears.
I don't tell this to many people (but I guess I am now!), but because of all this, it's quite likely the best species for catching the Wampus are probably Packer (for its smaller footprint) and probably Flapper and then Gollumer, as they are the thinnest when shown outside the town.