April 29, 2009 -- Many insects and animals, including humans, enter into a state of "fake death" immobility when threatened, but this seemingly passive frozen-with-fear state may be a selfish behavior that can lead to the killing of one's friends and relatives, according to a new study. For humans, this can happen when an attacker enters a building and starts randomly targeting victims. People who play dead often survive, while their fleeing colleagues usually aren't so lucky. The paper, published in the latest Proceedings of the Royal Society B, is the first to demonstrate the adaptive significance of playing possum, and how it's a selfish behavior. "Death-feigning prey increase their probability of survival at the expense of more mobile neighbors," lead author Takahisa Miyatake told Discovery News. Related Content:
Miyatake, a professor in the Laboratory of Evolutionary Ecology at Okayama University, and his team focused on a predator-prey system that, like the cartoon Road Runner and Wile E. Coyote, involves constant chasing. In this case, a hungry jumping spider frequently chases, bites and eats red flour beetles. The two species cohabit on rice bran or corn flour in cereal storehouses. The researchers conducted experiments to see how well death feigning beetles survived when alone, or with other individuals either of their own, or similar, species. The scientists also checked to see if chemicals emitted by beetles playing dead somehow made them unattractive or unpalatable to the hungry spiders, which were starved for a week before the experiments began. The chemicals didn't seem to make a difference, but having other moving individuals around did. During one experiment, around 60 percent of the beetles were eaten by the spider when they were alone and playing dead versus just 9.6 percent when additional mobile insects were nearby. "Spiders appear to rely on prey locomotion in order to catch prey, and in addition may rely on tactile movement signals to initiate the kill behavior," the researchers explained, adding that "selfish prey" playing dead then wind up sacrificing their "neighbors in the group or community." Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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