Well, well, well. You've moved past the tough enemies, like Elites, Grunts, and Brutes, eh? And now you think you're ready to tackle those pesky birds, the jackals. Well, there are a few things you'll need to know first:
To start things off, we must all remember that jackals are excellent shots, especially on higher difficulties. Probably a result of their higher senses of smell, sight, hearing, etc. They are cowardly, but they are also dangerous as heck. Individually, and close up, they are quite weak. If they have good cover, backup, or an energy shield, they can roast you though. The most important thing, however, is to REMAIN UNDER COVER!!!! This is more important that with any other enemies. The jackals have incredible aim, and they make quite thorough use of it. Since they only use Plasma Pistols and Beam Sniper things, those are the only two weapons that you must fear. They are unusually efficient with them, though.
So let's cover them, with the Pistol first.
When attacking Jackals that have the Plasma Pistol/Wrist Shield combination, you are better off. They don't have much in the way of a long range attack with these weapons. If you get too close, however, you are likely to get hit by an overcharged plasma bolt. This will drain your shield on any difficulty, and leave you EXTREMELY VULNERABLE!!! Make sure that you watch for the telltale green glow of the overcharging, and if you see it coming for you, duck. If you are unlucky enough to get hit, TAKE IMMEDIATE COVER! Don't even worry about getting shot at; what you want to do is hide and give your shields the time they need to regenerate. The best strategy to use against these foes is one of long range tactics. A single shot to the head is sufficient to incapacitate them, on any difficulty. Make good use of the notch in the sides of their shields to get a shot in edgewise. Make your shields count, too. Since most Plasma Pistol jackals travel in packs (mostly in threes), grenades are a good offense. Being unshielded, they can't really defend themselves. Be careful not to throw grenades directly at the shield, however, because they have a nasty habit or bouncing right back at you. Also, melee shots make a good last-ditch resort, but I wouldn't recommend trying to get that close...
Okay, let's move on to Sniper Jackals, shall we? The snipez0r jackals like to post and hide in dark crevices, holes, or anywhere else they can't easily be spotted. In a situation like this, the easiest way to find them is by following the purple beam of energy that they like to shoot at you. Follow it back to where they are lurking. On higher difficulties, these beams have the power to kill you in one shot. Period. They are probably the most annoying thing that you'll encounter in the game, next to Drones. But that's another story... Make sure you have a scoped weapon (Beam Rifle, Carbine, Battle Rifle, Sniper Rifle) before attacking them. I can tell you now that your chances of getting close enough to attack with mid-short range weapons are about as good as a one-legged man winning a butt-kicking contest, pardon the analogy. Aim immediately for any part of their body (you need not be picky) and shoot. Make sure you either have great cover, are invisible, are extremely lucky, or in the best case, ARE CONSTANTLY ON THE MOVE! If you shoot one and he doesn't die, there is a good chance that he will run away, at the same time drawing a Plasma Pistol. They are usually in the 'Arms-over-the-head' position, and are totally vulnerable at this point. Take these precious seconds to eliminate them. On the plus side, Sniper Jackals usually travel alone or in very small numbers (think pairs, or at the most trios). As long as you remember to stay covered and on the move, you should be just fine.