Carnivorous Pitcher Plant Outsmarts Insects, Gives Up Some Prey To Capture More

Scientists studying the behavior of an insect-eating pitcher plant -- named after its liquid-filled, funnel-shaped leaves -- have found that the plant possesses an ability to change its bug catching behavior in response to natural weather fluctuations. The researchers studying the insectivorous plant observed that it regularly allows some of its prey escape by “switching off” its trap.

“The plant’s key trapping surface is extremely slippery when wet, but not when dry,” Ulrike Bauer, a biologist from Bristol University’s School of Biological Sciences, who led the study, told Discovery News. “For up to eight hours during dry days, these traps are ‘switched off’ and do not capture any of their insect visitors.”

Such behavior, which, at first glance, would seem counterintuitive, might be the result of millions of years of evolution and natural selection, according to the findings of the study, published Wednesday in the journal Proceedings of the Royal Society B. Moreover, this unique ability provides the pitcher plant the opportunity to capture large batches of prey, giving it an evolutionary edge over other members of the species whose trapping surfaces are wet all the time.

For the purpose of the study, Bauer and her colleagues conducted experiments on wild carnivorous pitcher plants in the island of Borneo. They observed that when the nectar-coated collar of the pitchers were dry, ant “scouts,” which come in search of nectar, could move safely over them without tipping into the trap. These scouts then leave trails that other ants follow in large numbers, which are then captured en masse because the plant has made its trap wet and slippery by then.

Researchers also found that the plant had evolved to control when its trap was slippery and that “variations in humidity and weather conditions act as a switch,” intermittently activating and deactivating the trap, according to the study.

To test the evolutionary advantage provided by such a mechanism, scientists set up a control group of plants whose traps were kept artificially wet all the time. Over several weeks, they found that the natural pitcher plants caught more than twice the amount of insects than those in the control group.

“Of course a plant is not clever in the human sense -- it cannot plot. However, natural selection is very relentless and will only reward the most successful strategies,” Bauer reportedly said. “What looks like a disadvantage at first sight, turns out to be a clever strategy to exploit the recruitment behavior of social insects.”