Yes, they can. What's more, once trained they tend to stay trained. So familiarity with plants is an issue. If deer know there's something really tasty in your garden this year, because they've sampled it this year, then a small electric deer fence is unlikely to keep them out. This makes timing critical. Set up your garden electric fencing in the spring, before anything has sprouted. And, similarly, if you are protecting evergreens, set up your winter electric deer fencing in late summer or fall, so that you have a chance to train the deer and change established browsing patterns before food sources become scarce.
It can, reportedly in anywhere from one to four months. Also, deer that are not trained to avoid the electric fence may enter your area. So it pays to keep the electric fence well-maintained, ready to provide new training or periodic reinforcement of old training.
Yes. Deer are curious. They are attracted to novel things and explore them. So make your innovations quickly and completely. Don't leave a half-constructed electric fence out there for deer to explore and judge harmless before it is turned on. Also, consider changing the attractant on your baited electric fence from time to time. Part of its attracting power depends on novelty; and you definitely don't want your deer lures to be ignored by deer whose training is starting to wear off.
Overall, electric fences offer the most economical prospects for controlling deer. Besides being affordable, effective, and permanent, they open a broad range of options-everything from pet-safe electric fences around small gardens to powerful high-tensile electric fences protecting farms, estates, and institutions.
One good way is to train the deer to stay out before the plants are up. You can do this by erecting a simple one-wire baited electric deer fence in early spring (see Deer Fence Options and Kit Solutions. Power it with a electric fence charger like the Parmak Fieldmaster 2 or Solar Pak 12. Bait the electric fence with scent caps or with aluminum foil cups containing peanut butter, and renew the scent or peanut butter about every 10 days.
This sort of fence can sometimes fail where the deer pressure is intense, where grounding conditions are poor (see Are Ground Rods Important?), where the growing vegetables put out attractive scents themselves, or where one deer penetrates the barrier and finds good food inside. However, it is the first thing one should try, because in a large share of cases it succeeds.