SciSun: Bats, men and Robins   Leave a comment

Bats, those often-misunderstood night-hunters, generally are not associated with walnuts. Or any nut, for that matter, as nuts just aren’t the type of food bats crave. And rarely does any bat own a nutcracker. But this isn’t necessarily a story about walnuts; nor nuts in general; nor even, for that matter, bats; but rather how without these flying mammals, there would be fewer walnuts for us to eat; and far more bats reviewing their career choices.

Insects are the favored diet of most bats. Some only eat fruit and drink nectar; others hunt fish, frogs, lizards and other small animals; and a few drink blood, but not in the vampire-blood-sucking way which is entirely out of context, but in more of a lapping-up-blood droplets that causes little harm to the victim, and results in absolutely no cases of immortality. And, disappointingly for the bats, virtually no blockbuster movie deals.

In the Central Valley of California (the area between the Sierra mountains on the east, and the Coast Range on the west), is grown more than half of all fresh produce consumed in North America. By variety, that’s 88% of all strawberries; 90% of lettuce; 95% of tomatoes; 99% of walnuts within the United states, and three-quarters of walnuts throughout the entire world. An area of about 20,000 square miles feeds, in large part, over 500 million people.

‘The Birds and the Bees’ is not only a story parents must inevitably tell their children (unless the kids look it up online first); it’s only through these birds flying from plant to plant; and these bees collecting and spreading pollen between flowers; that produce of the Central Valley – as well as any farm, or field, or garden or backyard – grow and create the food that feeds us all.

Put all this together and what do you get? Not some bat-bee-bird-strawberry mutant (‘The BeakedBat that Ate Modesto: Bee Berry, Berry Afraid’); but a complex and delicately balanced, cooperative and interdependent array that humans, for all our achievements, have yet to understand, yet could easily destroy.

Scientists at the University of California, Davis, while researching the impact of insects on California crops – and what can be done to prevent insect damage to the California agricultural industry, estimated at contributing more than 40 billion dollars to the economy – found that bats, long known to contribute to insect control, have a much larger effect that previously thought; perhaps, in some crop infestations, bats may control more insects that birds, predatory insects, or any artificial method man has developed. The Codling Moth (Cydia pomonella) aside from having a rather harmless sounding name, is an introduced (non-native) species and one of the most destructive walnut pests. Adults lay eggs inside developing nutlets (another rather cute name. Who wouldn’t love a nutlet?), and when the moth eggs hatch – up to four generations per year – the larvae eat the nuts, as well as other parts of the walnut tree.

“Holy pernicious pests, it's a codling moth!”

“Holy pernicious pests, it’s a codling moth!”

Bats, however, seek out the flying, adult moths as dinner, a late night snack, early breakfast, or any time a moth crosses their path. Within a small study of just 150 bats, it was found on average each bat ate at least one moth per night, with some skilled – or very hungry bats – eating as much as two thirds of its body weight each night. That’s something like a 150 pound man eating 100 pounds of food a day, and although buffets might advertise ‘all you can eat’, that’s more of an advertising slogan, than a recommendation.

And it isn’t just one species of bat that enjoys this nighttime feast: The Mexican free-tailed bat (Tadarida brasiliensis); Yuma (Myotis yumanensis) and California myotis (Myotis californicus); Pallid bat (Antrozous pallidus); and four other species all are reported as living in, or around, walnut groves and other agricultural land, and it’s noted bats seem to eat more when their bat-houses (not Bat-Caves, that’s a different story) are placed directly within or on the edges of orchards. Based on some fast calculations, researchers estimate an average size walnut orchard, patrolled by averagely-hungry bats, will save each farm approximately $30,000 of walnuts each season from moths, along with yet unknown amounts of insects that target other crops, and allow more walnuts to be harvested for our cookies and cakes and nut-bowls. All for free, without any harmful side effects, and no need for humans to step in and try to improve anything. Because the bats, and the bees, and the birds, already have it all figured out.


Michonne Says: One time a nut fell off a tree and almost hit me on the head. I don’t know why that nut wanted to attack me because I never did anything to it. But later it was sorry it came off the tree because a squirrel came by and ate it. Now that nut won’t attack anyone again, so there.

Posted April 19, 2015 by ECOVIA eco-adventure® in ECOVIA Central

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