Insect Eating Bats Eat More Insects Than Birds in Tropical Forests

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If the early bird gets the worm, it is only because we haven't been observing bats the right way, at least not in the rainforests of Central America. It has long been thought that insects such as katydids and caterpillars exhibit night feeding in order to escape day-active birds. This theory has influenced the way in which researchers investigate insect herbivory in tropical forests. However, recent studies have shown that bats, not birds, are doing the bulk of the insect eating in both natural and man-made habitats. 

In order to accurately investigate the role of insectivorous bats play in limiting herbivory in tropical forests, researchers decided to look at the common big-eared bat (Micronycteris microtis). They wanted to find out exactly how much insect predation could be attributed to these nocturnal hunters. As it turns out, 70% of the bats diet consists of plant eating insects, which is quite significant. Extrapolating upwards, it was apparent that we have been overlooking quite a bit.

Using special exclosures, researchers set out to try to quantify herbivory rates when bats and birds were excluded. What they found was staggering. When birds were excluded from hunting on trees, insect presence went up 65%. When bats were excluded, insect presence skyrocketed by 153%! What this amounts to is roughly three times as much damage to trees when bats are removed - a significant cost to forests. 

To prove that it wasn't only natural forests that were benefitting from the presence of bats, the researchers then replicated their experiments in an organic cacao farm. Again, bats proved to be the top insect predators, eating three times as many insects than birds. This amounts to massive economic benefits to farmers. Bats have long been viewed as the enemies of both the farm as well as the farmers. Research like this is starting to change such perspectives. 

This certainly doesn't diminish the role of birds in such systems. Instead, it serves to elevate bats to a more prominent stature in the healthy functioning of forest ecosystems. Findings such as these are changing the way we look at these furry fliers and hopefully improving our relationship as well. 

Photo Credit: Christian Ziegler - Wikimedia Commons

Further Reading: [1] [2]
 

Nature's Radar

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Are you sitting down? You may want to before you read this. The relationship I am about to tell you about is pretty amazing. Coevolution is never a dull topic and the following example may be one of the coolest in the living world. 

Meet Marcgravia evenia. This vining plant species is native to Cuba and, like other members of its genus, relies on bats for pollination. This is nothing new. Many plant species utilize bats as pollen vectors. Bat pollinated flowers are often quite fragrant, using powerful odors to tap into the bats keen sense of smell. Marcgravia evenia is different though. This tropical vine taps into another batty sense, echolocation. 

Right above the flowers is a dish-shaped leaf. This leaf functions as a reflector for the bats sonar! Indeed, when tested, bats were twice as likely to find plants with these dish-shaped leaves than they were if the leaves were removed. This is an incredible coevolutionary adaptation! Because the vines are rare in the wild, anything that would increase the likelihood of a bat visitation would incur a considerable selective advantage. The dish-shaped leaves do just that. According to the authors of the paper, "the leaf's echoes fulfilled requirements for an effective beacon, that is, they were strong, multidirectional, and had a recognizable invariant echo signature." Nature never fails to amaze!

Photo Credit: Ralph Simon

Further Reading:

http://www.sciencemag.org/content/333/6042/631