1Jungle Jeopardy
Its bite force and night vision make the jaguar the jungle's "killer of killers," but the fer-de-lance pit viper's flesh-rotting venom is devastating.
2Deathly Bite
Orcas possess awesome speed, power and intelligence, but the rattlesnake, black widow spider and even the mosquito challenge them in dangerousness.
3The Freaks
Despite dwindling numbers, the Humboldt squid's beak is deadly, but the Brazilian wandering spider's fangs and venom are ruthlessly efficient.
4Killer or Saviours
Creatures such as the tarantula and the Gila monster are nightmares of myth and legend -- but also a surprising treasure trove for medical science.
5Pack Hunters
The oceanic whitetip shark is infamous for attacking shipwreck survivors. On land, packs of feral dogs are becoming a serious threat to human life.
6One Hit Wonders
The boa constrictor crushes the life out of its victims and the bullet ant's sting is painful, but the assassin caterpillar lives up to its name.
7Stop! Danger Ahead
A friendly-looking but deadly seal prowls the frigid waters off the tip of South America. The recluse spider's sting is painful, then rots away flesh.
8Best Left Alone
The murky rivers of the tropics contain a shocking surprise: the electric eel. The cute capybara and the furry llama can be surprisingly treacherous.
9Are They For Real?
The elephant seal's crushing head-butt is a killer skill, but the bites of both the Amazonian giant centipede and the vampire bat are horrifying.
10Stealth Hunters
The Brazilian yellow scorpion is one of the species' most venomous, but a tiny, parasite-bearing snail has a much bigger and more devastating effect.
11Killers: Myth or Reality
The dive-bombing harpy eagle feeds on monkeys and wild pigs, while the maned wolf is more the victim of bad PR than actual threat.
12The Final Countdown
The top 11 "fearsome finalists" from previous episodes, including bugs, bats, spiders and snakes, battle it out for the No. 1 spot.