They could easily make a gate.

I've read somewhere that wolves used to open gates to get to livestock before. Though I don't really agree with the cattle ranch anyway, so > > Yah.
When it comes to jumping over obstacles all I ever actually would jump over is a carcass. Even then one could easily go around it. The same with a tree. Half the fallen trees I know of I can easily walk around [heck, I can even walk through them sometimes xD]. Jumping over them is a fun option that puts the button to use, not something that's neccessary.
The cattle ranch [which I view as unrealistic as a whole] needs it to get at the cows. It's neccessary for that mission.
That's what I mean by neccessary.
With the way that this game defies gravity you don't need it to really jump on ledges either. 8| Now that I think about it.
I like discussing deep things, playing video games, and mentally torturing myself by studying C# even though I'm not a math person.