Halloween is the best time to dress up in scary costumes for humans. But for some animals, they don't need a holiday to terrorize the world with their appearance or with their predatory ways. In his book, Overcoming Animal & Insect Phobias: How to Conquer Fear of Dogs, Snakes, Rodents, Bees, Spiders & More, anxiety expert Dr. Martin Antony claims that six percent of Americans have an animal phobia. The following five creatures are the stuff of nightmares for people who panic at the thought of fatal animal encounters:

1)  Great White Shark (Carcharodon carcharias) 

With 3,000 teeth and 4,500 pounds of force behind every bite, great white sharks can live as long as 70 years. Though man is not the preferred prey of the great white shark, it's still responsible for the most number of fatal unprovoked shark attacks on humans.

2) Amblypygi (Damon diadema)

Called whip spiders and tailless whip scorpions, amblypygi thankfully do not possess venomous fangs. However, amblypygi can grab attackers or prey and puncture the victims with their spiny appendages.

3) American Alligator (Alligator mississippiensis)

The alligator's powerful tail, capable of breaking human bones, isn't its most dangerous feature. An alligator deals the most damage with its powerful jaws and is more than capable of killing humans because of sheer bite force along with a high risk of wound infection.

4) Rattlesnake (Crotalus horridus)

Rattlers can grow up to eight feet and rightly deserve the distinction as the largest venomous snake in the U.S. With a mouth that can open 180 degrees and swallow victims whole, the rattlesnake is both an efficient and deadly predator.

5) Sarcastic Fringehead (Neoclinus blanchardi)

Hiding inside shells or crevices, the sarcastic fringehead has a large mouth full of needle-like teeth and an even bigger territorial attitude. If anything wanders into its line of vision, the sarcastic fringehead will snap its jaws or swim in hot pursuit of the trespasser.