Oh, my, are my horses crabby these days. At least, Pilot is. He is a high-energy kinda guy who goes racing off at any possible opportunity just to burn off excess protein (thus, he gets grass hay, not alfalfa). This includes turning him out from the small (3-acre) pasture to the large (10-acre) pasture. Poof! He departs with a kick of the heels and a snort at full speed. With all the snow and ice we've had, despite his permanent access to the 3-acre pasture for the winter he is unhappy and hopes things will be different beyond the fence. Of late, he has taken to waiting until my back is turned gathering up hay and then gives the gate in the barn a good hard shove with his nose. Out he waltzes to explore the driveway. If I'm really lucky, I turn in time to prevent Nellie following him through. Twice I have been too late, and they've gone gallivanting up toward the house at a dead run, fortunately in the snow beside the driveway and not atop the ice in it. Even they aren't quite that stupid. Why not latch the gate, you say? It never used to be a problem. The bar slides hard now and doesn't catch as well as I think sometimes. Pilot always has to try...
He's bored. Bored horses are a problem. They tend to go sour in the pasture and the stall because they have nothing to do. This makes them crabby, often grabby with their teeth, and generally less fun to be around. Spending more time with them helps, and regular riding/work helps most of all, but let's face it, our heroes and heroines have better things to do than stand around petting their loyal steeds all day, and weather conditions don't always allow travel. Ergo, our heroes are likely to discover wooden fences with large scallops in the top boards from bored beasts chewing the wood. They may arrive at the stable to meet flattened ears and pushy demands for food/treats/attention/wide open spaces. Their sweet and loving companions may suddenly take after a stablemate for no discernible reason than that said stablemate is, em, available to be a target. In crowds, lower beasts on the totem pole suffer greatly from higher-rank critters' cabin fever.
How can you turn this to plot mayhem? Easily. My old gelding, Gallow, was an absolute fright every spring for the first three rides after the ice broke up enough to make the footing safe. I made sure there was still enough snow and deep berm alongside the road to run him into if he truly got stupid. Any long confinement will leave your horse champing at the bit (so to speak) and eager to get out and stretch his legs. Exuberant bucking from staid old creatures is not at all uncommon. Picture rabbits suddenly leaping into the air from a standing start, kicking out both hind legs for fun (otherwise known as a capriole). Now picture your unsuspecting hero sitting in utter surprise on nothing six feet off the ground.
This is a lovely thing to do to your hero's enemies. Fine. Give him the best horse in the stable for his getaway. The one that hasn't been ridden for three weeks. Give him the short-attention-span critter who loves to fiddle with ropes. Evil Overlord may be walking the next morning, tracking his mount, who has untied himself and everyone else and departed smartly for parts unknown. Give him the high-energy youngster who has the attention span of a flea and the manners of Godzilla. This child has difficulty concentrating through the saddle-up; after the first quarter mile of boring walking along beside everyone else he is going to be looking for entertainment, tired of having his attention redirected from yummy roadside plants to the trail. He will be lonesome stuck in his own space all by himself. He will start snuggling up to the nearest horse to the front or side, gawking at birds, clouds, large rocks, the tempting tail of the horse in front and pretty much everything else within his view because OMG I am so BORED!
Older horses just put themselves half to sleep shuffling along in the group, content to let everyone else look out for alarming things. Bored beasties look for ways to keep themselves entertained. This includes chewing/grabbing at the bit or shank (making inconvenient jingling noises with the right kind of bit, or sudden mayhem as he grabs it and bolts); playing with dangling bits of harness, grabbing at bushes as he goes by, fretting, dancing, head-tossing, and oh, my favorite, crowding, because he really wants to go somewhere else and everyone is in his way.
Do not be surprised if you come down to feed and your barn has been rearranged by bored Horsey. When Pilot gets out (not possible now that the gate latch sticks), rearrangement includes all of the grooming tools out of the brush box onto the floor, the lid off the dog food barrel and little crunchies all over everywhere, anything on any flat surface swept off in search of munchies, and a nice fat fertilizer deposit on the hay pile. Everyone's a critic. When Kalup got monumentally bored, you could expect to be picking things up for seventy feet in any direction. He didn't just investigate it; he played with it.
Let a bored horse loose in camp if you want a distraction in your story. You will have much fun and cussing trying to catch him, because almost invariably horses who have escaped lose their minds. The excitement of being loose outside familiar environs gets them prancing and snorting and sidling/running away from outstretched hands (even with treats) and suspicious-looking ropes and halters. You will be chasing them until you stop chasing them, at which point they will likely abandon the game and come to you. So a fool will continue to chase, and be delayed for an hour instead of five minutes. And if your neatly ordered camp was quietly torn apart by a nosy horse in the night, why, it gives the opposition all kinds of time to catch up and inflict whatever damage is necessary to your plot.
Bored horses. God love 'em. And keep 'em far away from me.