So I was thinking about the Timberwolves appearance in Spike at Your Service, and had some thoughts. Call it fan-lore theory or whatever.
There were two things that really caught my attention. First, when Applejack destroyed one of them, it's front legs kept going for a short time before going poof, and second, the bit about the merger of three Timberwolves into one big one.
I'm thinking that (among other things) there's one (just one) "wolf spirit" in the Everfree Forest, and it's extremely powerful and highly intelligent (it could also be good, evil, or neither). BUT... it has become disembodied somehow, and can't maintain any cohesion. Instead of occupying one place, this spirit is spread thin across the entire forest, blowing around uncontrolled like a fog, but generally anchored to the confines of the forest. In this state, it's power and consciousness is so diluted that it can't act or even think for itself. When it happens to condense into higher-concentrated pockets of spirit, it instinctively tries to use it's increased power to possess inanimate objects, like fallen branches and leaves, and assembles them in a familiar shape, a wolflike one. In this confined and familiar form, the spirit is able to concentrate and act in ways it couldn't when it was formless, but individual Timberwolves aren't concentrated enough to reach anything more than beastlike intelligence. Individual Timberwolves gather into packs because their spirit wants to reassemble, but they never merge into Super Timberwolves because the accumulated spirit in any one given Timberwolf is unwilling to let go of it's desperate hold on wolf form in order to join with another. I would also suggest that maintaining possession of these inanimate objects is exhausting to the wolf spirit, but that while a Timberwolf travels in the Everfree Forest, new spirit clings to it and adds to it's strength, replacing the spirit that has let go from exhaustion. This would maintain a sort of balance in the Timberwolf population.
It's also interesting to note that this spirit only possesses the inanimate, fallen pieces of the trees in the Everfree Forest (aka timber). It doesn't appear to possess rocks. There's something about the trees in the Everfree Forest that allows this spirit to possess the dead ones.
When Applejack smashed three Timberwolves all at the same time in the same location, she created a pocket of triple-dense spirit that was able to unite as one greater, more focused power, and was able to possess not only the timber remains of the three, but it pulled a pretty large amount of fresh timber from the edge of the forest.
I would suggest that the Super Timberwolf was much more intelligent than the individual Timberwolves, because when Spike threw a rock down it's throat, it was making human gestures like "excuse me" and "give me a minute". Also, it's probably a good time to remember that rocks (along with any else that isn't Everfree timber) seem to be alien to the makeup of a Timberwolf, which was why he choked on one. Although I'm also speculating that the Super Timberwolf might have been conscious enough to become somewhat self-aware, and it realized that a rock in the throat should have caused choking, which prompted a coughing-response, which didn't make him feel better, it just felt weird, and why am I coughing up wood? Ohmygod, I'm made of wood! Aaaahhh! What am I!? *dies*
And then this theory brings me to Family Appreciation Day, where it was shown that Timberwolves are sensitive to the energies the precede the appearance of zapapples. They howl before any other creature appears to know they're coming. It's not clear if this is a good howl or a bad howl. Like, do the Timberwolves love the zapapples (and/or just the energy buildup) or hate them? Or are they somehow responsible for it (like, is the wolf spirit the one making zapapples)? One thing that I think is interesting is that the zapapples all disappear after one day on the trees. Or rather, they all disappear when they hit maximum ripeness. Is the wolf spirit eating them? Are Granny Smith and Filthy Rich getting rich by stealing the food out of a wounded god's mouth? Also, when the zapapples all disappear, the Apple family gets to keep the ones that have already been picked, otherwise known as the ones that have become timber. Cue the spooky music. I have no answers.
Remember also that Celestia and Luna's original home was in the middle of the Everfree Forest, and that Celestia told the Apples that they were allowed to move in next door, but that they should keep their noses out of the forest (which of course they didn't).