Operation Cat Drop

research blogging iconIn the news recently: Operation Rat Drop, where tylenol-laden mice were dropped from planes over Guam. It’s not a bizarre headache remedy; the idea is to try to kill brown tree snakes (a non-native invasive species) when they eat the mice.  Acetaminophen kills snakes. Who knew?

That reminded me of a similar–but much odder–project: Operation Cat Drop. It’s an oft-told story about DDT and unintended consequences.  I was excited to see it had recently been covered in a journal!

In 1955, a malaria outbreak in Borneo was fought by spraying DDT and other pesticides. Several unintended consequences were observed after the sprays, but time and distance have muddled them quite a bit.  The basic claim is that local cats died after the sprays, and this caused an explosion of rat populations, which lead to increased human disease. The RAF then (in the more exciting versions of the story) parachuted in 14,000 cats to remote Borneo.

Some things are known and documented; one unintended consequence that did occur post-spray was that caterpillars eating the roof thatch of homes increased 50%, with associated roof damage:

 “The WHO team sent to investigate determined that moth larvae (caterpillars) living in the thatch were able to distinguish the presence of DDT and so avoided eating thatch sprayed with the chemical, whereas their parasites, small chalcid wasps that injected their larvae into the caterpillars, were highly susceptible to DDT, causing their decline and the subsequent increase in caterpillar.”

This is a fairly classic pattern, where pesticides disproportiately affect natural enemies, or living organisms that act as natural brakes on pest insect populations.

It is also known that cats did often die after DDT sprays, and this was observed in several different countries on different occasions, including in Borneo. It would make sense that cats would eat rats and insects (and, in some versions, geckos) affected by the sprays, and the pesticide would biomagnify in their kitty bodies. That, however, does not appear to be the case;  cats’ habit of grooming themselves and ingesting residue of the pesticide was what allowed them to receive a lethal dose.

Which leaves us with the parachuting cats.  There was a rat problem in the area, and there is a record of 20 cats being dropped in Borneo by the  British RAF, along with some chickens, by parachute.  But that’s it. They weren’t in little harnesses; they were in special containers that would cushion the drop.

kitty and parachute

It’s a fascinating story of how something basic took on a life of it’s own. The paper I’ve cited below suggests that some of the story’s inflation in kitty numbers can be attributed to an expatriate Brit with a big ego that initially  started the rumors.  I don’t have access to his original document, which included little drawings of cats in individual parachutes, so I have done my best to recreate them here.

From there, the story was reproduced and  took on a life of it’s own–I’ve seen versions where all the cats landed in the sea and drowned, versions where there were 10,000 cats, and versions where high-velocity falling cats killed people when they fell on them.  All false, but far more interesting than reality.

Before anyone begins to trot out the usual “DDT will save us all” crap, I want you to read that paper and notice that it clearly lays out a whole sequence of unintended consequences from DDT sprays, including the problem of resistance from as early as in the 1950s.   This paper is a reminder that we should not be uniformly pro- or anti-DDT;  we should make pesticide decisions based on the best available, real evidence. Not propaganda.

Full Citation:
O’Shaughnessy, P. (2008). PARACHUTING CATS AND CRUSHED EGGS The Controversy Over the Use of DDT to Control Malaria American Journal of Public Health, 98 (11), 1940-1948 DOI: 10.2105/AJPH.2007.122523

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