Rats with wings. That's what some people call bats. They are notoriously creepy, flying around at night, swooping through the air with their sneaky sonar guiding them. Then there is the whole vampire thing. Yes, some bats survive by consuming the blood of other animals, but horror movies have turned this into way more than it really is. Still, it's another thing about bats that make people freak out when a bunch of them circle around.
When they aren't buzzing through a belfry or posing for Halloween decorations, they hang out in dark caves or the hollows of trees. Upside down, with their wings clasped around them like a like a cape, resting until they can prowl the night sky again.
What many people don't realize however is that bats are extremely good for the environment. They eat insects that can devastate crops, and a new study shows that bat guano, yes, that's poop, is helping to fertilize a certain tree in the rainforest.
Part of the problem in many tropical rainforests is that plants need specific nutrients to grow. While lush in many ways, the rainforest is typically low in two crucial substances, phosphorus and nitrogen. Biologists studying the ecosystems have in the past found that plants can get these necessary fuels for growth from animals that live in the rainforest. But it was not known until recently if the same could be said for trees.
Scientists from the University of Tel Aviv and the Doñana Biological Station in Sevilla along with their colleague Christian Voigt from the German Leibniz Institute for Zoo and Wildlife Research recently studied almond trees in the rainforest of Costa Rica to see if there was any benefit to the trees from the thousands of bats that hang out there. Cavities in the trunks of the almond trees are quite like mini bat caves, providing a place for bats to sleep during the day. Their research and results were published in the journal Biotropica.
The team compared trees that hosted bats to those that did not, but they did so by testing specifically for a form of nitrogen contained in animal tissues and excretions, 15N, a stable isotope form of nitrogen. What were the results? Trees that did not contain bat roosts had significantly lower amounts of 15N in their seeds that the trees that were populated with bats. Because the nitrogen was concentrated in the seeds of the almond trees, it winds up being directly used for reproduction. This is the first research to show that trees, like plants, can benefit from this kind of indirect fertilization.
In a statement about the study, lead researcher Voight said,"Thus, we were able to track nitrogen from bat guano into the seeds of Dipteryx trees. Nitrogen may be assimilated by the fine mesh of roots that we found in all natural tree cavities."
The study didn't stop there however. Two other considerations were accounted for in the research. The first was size. Size matters, and with bat colonies, the more the merrier. The team found that the more bats there are in a colony, the better the result for the trees they inhabit. It also matters what kind of bats roost in the trees. The species that produced the most nitrogen? Vampire bats. Rather than being blood-sucking parasites, it appears that vampire bats provide greater amounts of the nutrients needed for the trees to thrive than their less scary counterparts, the fruit bats.
The research team also found that there may be a benefit to the trees in one ecosystem from the foraging the bats do outside of the forest. Some of the bat species act almost as a delivery service bringing nutrients from pastures or other areas to the trees.
Check out the video below for more information about how bats benefit their habitats.
Source: Science Daily, YouTube, PBS, Forschungsverbund Berlin e.V. (FVB)
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