Wednesday, February 3, 2021

Answer: A war on pests?

 When too many animals group together, it can be a problem.     

[ Comment: Sorry this was a delayed by a week.  It's been a busy time. ] 

This week's Challenge highlights a couple of wrong-place & too-many times when people went to work to fix the problem, but it completely and utterly failed.  These aren't hard, but are pretty amazing in their details.  Can you figure out what's going on in each of these Challenges? 

1. Too many birds really can be a problem.  In one famous incident, an entire "War" was declared on a particular kind of bird.  Big guns were brought out, the campaign planned, thousands of shots were fired, and it all ended in a dismal failure.  Where was this war?  What kind of birds were being fought? And in the end, what happened?  

This wasn't too hard, but fascinating to learn about.  I'd heard about a kind of "war against big birds that ended badly," and so was naturally curious to learn more.  

    [ war against birds ] 

leads quickly to the Wikipedia and Scientific American articles about the Great Emu War. 

The short version of this: Shortly after World War I, large numbers of discharged veterans were given land by the Australian government to take up farming within Western Australia. Unfortunately, the emus (large flightless birds) were enjoying the farmer's fields as well.  


By late 1932, there were 20,000 of them wreaking havoc on the wheat farms of the beleaguered veterans, and even these trained riflemen could not put a dent in their numbers.  

The veterans asked for help from the Australian military, which was more than happy to send soldiers, machine guns, and ammunition. The "war" was conducted under the command of Major G. P. W. Meredith of the Seventh Heavy Battery of the Royal Australian Artillery. 

Unfortunately, when the soldiers went to shoot the birds, they scattered effectively and evaded much damage.  After the first attempt, the total number of emus killed was roughly 50--after several thousands of rounds fired.  A couple of weeks later they tried again, with not much better results.  Tens of thousands of rounds fired, and only about 1,000 emus killed.  In the end, it took around 10 shots per each emu removed.  The technology solution did not work well.  

However, Meredith's official report noted that his men had suffered no casualties.  

After 1929, exclusion barrier fencing became a popular means of keeping emus out of agricultural areas (in addition to other vermin, such as dingoes and rabbits).  It proved to be cheaper and much more effective than shooting them.  

This war was won by the emus.  

A wonderful contemporary film showing the Army's Lewis guns in action.  

There were, of course, other battles against birds.  As reader anon0750032j pointed out, Mao launched a massive extermination campaign against "The Four Pests,"  ( 除四害). The four pests to be eliminated were rats, flies, mosquitoes, and sparrows. The extermination of sparrows is also known as Smash Sparrows Campaign ( 打麻雀运动) or Eliminate Sparrows Campaign ( 消灭麻雀运动).  This was another kind of disaster--the lack of birds resulted in severe ecological imbalance and became one of the causes of the Great Chinese Famine. In 1960, Mao ended the campaign against sparrows and redirected the fourth focus to bed bugs.  (That sounds like a futile campaign.)  

Luckily, they didn't bring out the heavy artillery, or I'm sure even more damage would have happened. 

2. Too many insects can be a problem as well, especially when then fly around en masse.  Can you find the largest grouping of insects that caused enormous problems with the local agriculture?  Why do those insects group together?  And why do those groupings finally end?  

I did searches very much like Regular Readers: 

     [ large insect swarms ] 

And, like many of you, I found that locusts form the largest aggregation of insects.  With a couple of clicks I found the U. Florida Entomology Department's Book of Insect Records, which tells us that: 

The Desert Locust, Schistocerca gregaria, forms the largest swarms. In early 1954, a swarm that invaded Kenya covered an area of 200km2. The estimated density was 50 million individuals per km2 giving a total number of 10 billion locusts... 

On the other hand... I also found a New York Times article documenting the 1875 locust swarm that was the largest recorded in North America.  It was estimated to be 1,800 miles long and 110 miles wide (512,817 km2).  That's equal to the combined size of Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island and Vermont!

Of course, it's difficult to compare these estimates without good communications technology (to get a single measure of the swarm size at one point in time), but if the estimates are close to correct, the 1875 swarm in North America was about twice the size of the Kenya swarm.  

In both cases, these swarms were immensely devastating, eating all of the crops--seeds, fruits, and even the fence posts.  

And yet, in North America, a mere 28 years later, this seemingly indestructible enemy vanished. There hasn't been a sizable locust swarm in for over 100 years (see: Wikipedia article on Rocky Mountain Locusts).  In fact, these locusts are now extinct, apparently due to changes in land-use patterns over the past 150 years in central North America which removed their breeding grounds.  

My query about "why do these swarms happen" was: 

     [ locust swarm causes ] 

Leads to a plethora of articles about relatively recent discoveries about locust swarming behavior.  One source (LiveScience) points out that "[locusts] undergo a dramatic transformation when there are many other locusts of the same species nearby. The locusts shift from what scientists call the solitary phase when the locust is alone, to the gregarious phase when they swarm together. 

As it happens, the specific signal that begins the shift from solitary to gregarious varies from species to species.  The desert locust  (Schistocerca gregaria) can shift into the gregarious phase with a touch on the hind legs, while the sensitive area on the Australian plague locust (Chortoicetes terminifera) is its antennae. These triggers seem to boost levels of serotonin, the same chemical associated with mood in humans.  That serotonin boost, in turn, causes locusts to start to move together, ultimately snowballing into ever larger accumulation that become damaging swarms.  

NOTE:  There's a 17-year cicada brood emerging this spring.  It will be tremendous, and look like and sound like a swarm, but they don't typically cause problems. Luckily, aside from making a tremendous din, cicadas typically are harmless and represent a huge windfall food supply for other animals. They don’t eat crops (although they occasionally feed upon tree sap); they just want emerge into the sunshine, find a mate, create the next generation and die (incidentally, delivering a huge amount of food to animals that feast on cicada bodies).  

I was in the Washington DC area during the last cicada brood emergence, and it's true--they can be VERY loud and eerie-sounding.  But they do not bite.  However, they do fly, and love to crawl around... which was surprising when I found a couple crawling up my leg just above my socks!  

A 17-year cicada, coming out in North America later this the millions! 

SearchResearch Lessons 

This wasn't a difficult task, but there's a good tip here.. 

1.  Use the most specific term you can to describe the phenomenon you seek.  In this case, the term swarm was the perfect descriptor.  Take note of speciality terms like this as you do your initial reading, and then use those terms for your second, third, and fourth queries.  

Search on! 


  1. With article mentioned : What makes a locust a locust? From 2020 (Locusts or Gremlins?) , mentions: ".....When environmental conditions are right — usually when there's a lot of rainfall and moisture — something dramatic happens...The ability to change dramatically like this in response to environmental conditions is called phenotypic plasticity.

  2. …so much for self-regulation…
    the BBC - exploders of myths… meh
    White Privilege Wilderness
    Nils Chr. Stenseth - a Lemmingologist - ⌘F 'lemmings'
    Goo books - The Biology of Lemmings
    "White Wilderness" was filmed in Alberta, Canada, a landlocked province, and not on location in lemmings' natural habitat. There are about 20 lemming species found in the circumpolar north - but evidently not in that area of Alberta. So the Disney people bought lemmings from Inuit children a couple provinces away in Manitoba and staged the whole sequence.
    quote source
    Gordon Jarrell stands beside the mitochondrial DNA sequence from a pika
    from way back in 1996…
    nor explode
    tech exploding…
    mental floss & Blink-182
    Dude Ranch (1997)
    the other direction
    a breakdown