In response to John Simmon's, now ancient, request for clarification on the
efficacy of machines that claim to repel animals with ultrasonic noise and
electromagnetic radiation:
 
"Rodent Repellers: More Proof Is Needed".  Pest Control, Aug. 1977, pp 26-8.
In 1977, the "experts" stated no manufacturer had sufficient proof to
substantiate their claims.  The claims were "coupled with the almost mystical
explanation of how they [the devices] work".  The same experts also did not
have the data to completely dispute the claims, but it was early days.
 
14 years later we have the following excerpts from:
"Ecology and Management of Food-Industry Pests". Richard Gorham ed. FDA
Technical Bulletin 4. Association of Analytical Chemists, Arlington, 1991, 595
pp.
 
"Recent claims for ultrasonic repellers...should be regarded with caution.  No
experimental or test data documenting efficacy have been provided, but this
does not deny the possible value of such devices". W.B. Jackson, Ch. 16 in
Gorham 1991, Pest Bird Ecology and Management, from page 231.
 
Yup, no data will leave that possibility if you play science by the rule book.
 
 
The discussion gets better though, read:
S.C. Frantz and D.E. Davis, Chapter 18 in Gorham 1991, Bionomics and Integrated
Pest Management of Commensal Rodents, from pages 299-300.
 
"Though data are limited, it appears that rats and mice can be moved about or
have their activity areas and travel routes altered by inundating such areas
with ultrasound of proper frequency and intensity."  The authors point out that
ultrasound will not turn corners or penetrate walls, leaving a "sound shadow"
behind any obstructions.
 
The authors also state that the devices are impracticable because of sound drop
off and absorbtion.  Canada has guidelines for those wishing to claim efficacy
of their devices, where 90 dB is the minimum intensity at which the government
will begin to consider the efficacy claim.  This requires that the mice move to
within a few meters of the device in order to be repelled.
 
Sort of the same relationship I have with my TV.
 
Some of the claims also seem to have lacked control experiments, or measured
the sound at the source, not where the rodent would hear it at the floor.
 
Oops.
 
Now the vendors say you can use the devices to herd rodents into other traps
into the "sound shadows".
 
"Today, manufacturers generally state that ultrasound is most effective when
used in conjunction with other interventions.  Because these other
interventions can substantialy reduce or eliminate rodent infestations without
"help", the extent to which simultaneous use of ultrasonic devices might add to
or "coattail" upon the effects of the other methods is difficult to establish."
 
The authors conclude that there is not enough data to do a cost benefit
analysis of this latter approach.
 
Frantz and Davis, on the electromagnetic devices marketed to control pests:
 
"Manufacturers claimed that rats and mice ... were either killed or prevented
from eating, drinking, or mating by the magnetic field emitted by such
devices."  Manufacturers also claimed domestic animals and caged animals were
not affected.
 
"Although such outlandish claims might appear to have been written for people
who had only recently learned to walk erect, the successful marketing of EM
devices was remarkable.  The first device was marketed in 1976 and within a few
years there were some 30 manufacturers/distributors in the USA, with annual
sales of several million dollars."
 
And for the sceptics who like to sully opinions with data, the field strength
measured at 3 meters from the devices was less than than that provided free by
the earth.
 
The authors cite:
Environmental Protection Agency. 1981. Investigation of efficacy and
enforcement activities relating to electromagnetic pest control devices. EPA
340/02-80-001. Washington D.C.
        EPA's conclusions:  NO biological effect measured in rats, mice, or
other species tested.
 
The U.S government used the courts to pretty much shut down the electro-
magnetic pest control industry by the early 1980's.
 
 
Tom Strang
Conservation Scientist
Canadian Conservation Institute
 
"Shut the door, wipe your feet, clean your room, don't eat in bed..."
        My mom, on pest control.