Can* multiple skills be used in a versus test, or should there only be one skill versus one skill? In the case of the former, can* the versus tests be unequal? For example, if testing against the season, can* players use two different skill rolls versus the season’s one roll?
*this word is used hesitantly and with the implicit understanding that a GM ‘can’ do whatever (s)he likes… 
Can* you give us an example or two?
Yes, I can*.
Ex. 1: The patrol is escorting a cart, and it has become stuck in the mud. In order to get it unstuck, the players need to roll versus the season (let’s say Spring). This would require a Laborer vs. Season (6). If the players want to use a lever (a branch, for example), could I allow them to test Laborer and Scientist vs. the Season, or is one just a helping die for the other?
Ex. or 2: The patrol’s mission is to find and drive off/remove a raccoon that is raiding larders. Doing so requires a Scout vs. raccoon (Nature 8) to locate it. The players, instead of the group pursuing as one, want to split up to try to flush out their opponent. Would I allow each patrol member a Scout test (totaling all successes) versus the raccoon’s one test to locate it, or is the overall strategy simply a way to add helping dice?
I suppose the crux of my inquiry might be: Is there such a thing as a complex versus test?
In example 1 if the players already have a branch to use as a lever they could use it as a tool which gives +1D. A second mouse with the scientist skill could describe and use the plan for +1D using teamwork. If the mouse making the test has an appropriate wise such as cart-wise or weight-wise then he could use the I Am Wise rule to gain a +1D. You never add skills together like you describe. The player could spend a persona point to tap nature and add dice equal to his nature rating to the roll. But as this is outside his nature he’d be taxed by one if successful or by the margin of failure if still successful.
In example 2 the mice seem to be helping each other by splitting up. Determine who is making the test and add helping dice for each appropriately described teamwork.
Thanks.
Ah, the nature* of Mouse Guard. You’re either successful at what you try… or you’re still successful at what you try. For me that one sentence really sums up one of the most important differences between Mouse Guard and just about every other RPG I’ve played. Well said!
Uhh, that’s me typing the wrong words. There was no special insight from me.
And to think, I edited my post several times before hitting “Post”, initially assuming it was a typo, but eventually giving you the benefit of the doubt. I’ll know better next time.