There are many products available to consumers that help guarantee their safety from various forms of predators, human and animal alike. Most typically self defense deals with human targets as it is typical for a human to human encounter to happen far more frequently than an animal to human interaction. However, there are different devices sold regularly which have specifications towards one, or equal effects on both.
Of the various devices out, the general categories fall under Stun Guns, Tasers, Pepper Sprays, Alarms, and other lesser devices. Most of these defensive aids are meant to look like common goods that are indistinguishable from real items at a distance. This helps put an attacker at the disadvantage because they aren't then prepared for retaliation. Also, instead of just prevention, some of the devices provide continuous delivery or attracts attention. The following examples are effective tools against human targets.
The low current but high voltage efficiency a Stun Gun provides isn't enough to affect an assailant's heart, but will certainly hamper their nervous system temporarily. Using a voltage stepper within the device, it is possible to take the energy of a simple 9-volt battery and turn it into a shock of 100,000 to 800,000 volts or more depending on the model used. This high frequency pulse sent into a muscle will convert the blood sugar into lactic acid and result in a loss of energy in that region, causing sluggish movements. Shorter periods of contact has lesser effects and are more easily overcome, while longer than three seconds will keep the target down, weak, and disoriented for several minutes. Stun Guns are often less "gun" and more handheld energy discharger.
Similar in principle, Tasers also deliver a shock to a body and leave it disoriented and immobilized until help arrives or the would-be-victim gets away. Much more like a gun in principle, the Taser will fire two projectiles that are propelled by compressed air towards its target and imbed in their skin. Attached to the Taser and the darts are metal wires that carry a continuous charge from the main body of the device into the body of the assailant. Typically Tasers are left behind as the victim escapes. This method of delivery allows additional time for the escape of the attacked individual to get away or find help. As they do fire projectiles, there are many countries and states where they are illegal and criminal charges will be pressed onto those that carry them.
One of the best and most often used self defense products is the Pepper Spray or Mace. Usually disguised to resemble lipstick or similar small container, Pepper Spray is fired from the container in bursts or jets of foam or mists into the targets eyes. The spray then temporarily blinds the target with a burning sensation in their eyes that causes them to tear up. It has a similar effect on the nose, so a full facial burst will easily buy time for an escape.
The Personal Alarm is less a defense device and more a deterrent and caller for help. Usually in the form of a small box on the belt or other locale, the alarm is tripped when a pin is pulled from the device and allows it to emit a loud wail or screech that instantly alerts anyone to the situation and causes a momentary hesitation in the threatening individual. As they do nothing to the assailant physically, it may not save a person from an unfortunate ending if the assailant has control of their senses. It is the least effective device to save a victim.
For non-human targets though, all four will work well in smaller animals. While a larger predator may not be as affected by electric shocks, most animals would fair poorly against Pepper Spray or the Personal Alarm, as their senses are much keener than a human's sense. The best thing for when it comes to self defense in any case, human or animal, is to avoid the environment where an attack would be most likely. If that is unavoidable, then it is best to know your options for self defense products, and how to use them.