For a nice rest, a Hardwicke’s woolly bat (left) likes to snuggle into the vase-shaped leaves of the carnivorous pitcher plant (right).
By Stephen Ornes
Babies nap in cribs; bigger people doze in hammocks. Cats may curl up in sunbeams. If awards were given for the most interesting places to nap, neither people nor felines could compete with a bat that lives on the Island of Borneo.
This little beast, called the Hardwicke’s woolly bat, likes to curl up smaller than an iPod and snooze in comforting leaves of a carnivorous plant called a pitcher plant. The plant is said to be carnivorous because it eats bugs — like the more familiar Venus flytrap. Pitcher plants have nothing to do with baseball. They get their names from the vase-shaped leaves, which are perfectly designed for trapping food. And it is inside this “pitcher” that the bats nap, right above the plant’s throat.
But the bats are in no danger of being digested. Instead, the new works suggests, this napping choice might be part of a relationship that is good for both bat and plant.
Ulmar Grafe, a tropical ecologist at the University Brunei Darussalam in Gadong, led the study. Gadong is in Brunei, a nation on the northern tip of the Island of Borneo, which is a huge South Asian island that belongs to Indonesia, Malaysia and Brunei.
In the summer of 2009, Grafe and his colleagues attached electronic tags to 17 bats in a forest in Brunei. The team tracked each animal for an average of six days. Even though the forest offered different kinds of hideaways for the bats, the creatures kept returning to the leaves of one kind of pitcher plant.
Grafe decided to pursue the project after one of his students discovered a bat napper in a plant. He told Science News that, in the past, plants with bats “were always put off as coincidence.”
“To my knowledge, this is the first report of bats roosting inside pitcher plants,” Thomas Kunz, a bat expert at Boston University, told Science News. Kunz did not work on the study. To roost is to settle down for sleep, and the high population of bats sleeping in the plants suggests the plants are more than just convenient beds.
The scientists looked at more than 200 pitcher plants in the area and found that almost 29 percent had hosted a sleeping bat some time during the six weeks of the study. Pitcher plants can protect napping bats from predators during the day. But the bats aren’t the only ones to get something out of the siesta: pitcher plants may benefit, too. Napping bats leave their poop behind — which is a rich source of nitrogen for the plant. Grafe and his colleagues took tissue samples from the pitcher plants that had hosted bats and found higher amounts of a particular isotope of nitrogen. An isotope of a chemical has the same basic properties, but its atoms are slightly different.
Grafe says he thinks bats and pitcher plants help each other out. The bats get to sleep, and the plants get nitrogen. In ecology, two different organisms have a mutualistic relationship if they both benefit from the arrangement. In many cases, they need each other to survive. Even though plants probably don’t need the bats, they do benefit. Grafe suspects the two different species do have a loosely mutual relationship.
Other scientists say mutualism is possible, but it might be too soon to say for sure. “I've seen people slap the [word “mutualism”] on the most casual of relationships,” Barry Rice told Science News. Rice is an expert on carnivorous plants at Sierra College’s Rocklin campus in California. “Sorting out the relationships among life forms can be more complicated than a teenager's Facebook account.”
POWER WORDS (adapted from the Yahoo! Kids Dictionary and other sources)
mutualism An association between organisms of two different species in which each member benefits.
nitrogen A common element with the symbol N. Nitrogen makes up 78 percent of the Earth’s atmosphere and is found in every living tissue. Nitrogen is often added to agriculture and gardens as a fertilizer.
isotope In chemistry, a type of element (gold or sulfur, for example, are elements) that has the same chemical properties as another type, and the same number of protons in its atoms, but has a different mass because it has a different number of neutrons in its atoms. Carbon-14, for example, is carbon with 14 neutrons and is an isotope of carbon-12, which has 12 neutrons.
carnivorous Describes a life form that eats meat or flesh (including insects).
POWER WORDS (adapted from the Yahoo! Kids Dictionary)
Milius, Susan. 2011. “Deadly For Bugs, Perfect For Bat Naps,” Science News, January 25. http://www.sciencenews.org/view/generic/id/69133/title/Deadly_for_bugs,_perfect_for_bat_naps
Sohn, Emily. 2007. “How to fly like a bat,” Science News for Kids, May 9. http://www.sciencenewsforkids.org/articles/20070509/Feature1.asp
Sohn, Emily. 2005. “Vampire bats on the run,” Science News for Kids, March 23. http://www.sciencenewsforkids.org/articles/20050323/Note2.asp