From ANIMAL PEOPLE, December 1996:

Our friend Bob Plumb, of the Promoting Animal Welfare Society, in Paradise,
California, recently became aware of a feral cat problem at a park in nearby Chico. A large
colony was accused of killing songbirds, and slated for destruction by animal control.
Plumb, a retired physics teacher, combines his longtime philanthropic interest in
humane work with applied math skills. He especially likes to solve problems through modeling,
projecting the outcome of various strategies based on known statistical parameters
––and over the years, he’s become rather good at it.
When Plumb worked out the numbers pertaining to the park in Chico, he found
that the popular approach, trying to catch and kill all the cats, wouldn’t work. Catch-andkill
capture efficiency, in that habitat, stood little chance of exceeding the reproduction
rate. In effect, using catch-and-kill would amount to farming cats, sending each season’s
“crop” off to slaughter just in time to open hunting territory to the next round of kittens.
The benefit to birds would be nil.
Plumb also modeled neuter/release, which he calls TTAVR, short for trap/treat
(for treatable medical conditions)/alter/vaccinate/release, to cover all steps. Adoptable cats
would be put up for adoption; seriously ill or injured cats would be euthanized.
The first-year costs, he found, would be far greater, since neutering a cat costs
about five times as much as killing the cat and disposing of the remains. Over a three-year
period, however, the costs would be the same, as the neutered park cats ceased breeding.

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