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Defense and Attack Strategies and Mechanisms in Biology 343

have minimal effects on the environment. Unlike conventional, lethal, weapons that destroy their
targets principally through blast, penetration and fragmentation, non-lethal weapons have rela-
tively reversible effects and affect objects differently (Alexander et al., 1996).

13.2 ACOUSTICS

13.2.1 Blast Wave Projector

Energy generation from a pulsed laser that will project a hot, high pressure plasma in the air in
front of a target. It creates a blast wave with variable but controlled effects on hardware and troops
(Alexander et al., 1996).
This could be akin to cavitation bubbles that are the loudest source of sound from ship
propellers.
Snapping shrimps (Stomatopods or mantis shrimp) are very noisy; it has been long assumed that
the noise was caused by their claws closing. In Odontodactylus scyllarus, the sound is caused by the
collapse of cavitation bubbles due to the high speed at which the claw moves, powered by a highly
elastic part of the exoskeleton. The shrimps appear to use cavitation to stun their prey (small crabs,
fish, and worms); it certainly wreaks havoc with the shrimp’s own exoskeleton. Although the claw
is highly mineralized, its surface becomes pitted and damaged; stomatopods moult frequently and
produce a new smashing surface every few months (Patek et al., 2004).

13.2.2 Infrasound

Very low-frequency sound that can travel long distances and easily penetrate most buildings and
vehicles. Transmission of long wavelength sound creates biophysical effects; nausea, loss of
bowels, disorientation, vomiting, potential internal organ damage or death may occur. Superior
to ultrasound because it is ‘‘in band’’ meaning that its does not lose its properties when it changes
mediums such as from air to tissue. By 1972 an infrasound generator had been built in France that
generated waves at 7 Hz. When activated it made the people in range sick for hours (Alexander
et al., 1996).
Whales are certainly able to generate low frequencies (15 to 30 Hz) which they use for
communication over long distances (the capercaillie, a ground-living bird of the Scottish wood-
lands, uses low frequencies for the same reason) but they have not been tested for any damaging
effects (Croll et al., 2002).
Although it does not really belong to ‘‘infrasound,’’ animals (e.g., frogs, birds, and deer)
advertize a false impression of exaggerated size by making low frequency sounds (Reby and
McComb, 2003). The implication for other animals is that a low noise can only come from a
large resonant cavity, so the animal producing the noise is probably large and therefore probably
strong. Producing low frequency vibrations is therefore a premium especially if the animal cannot
be seen and the assessment of size can be made only from the frequency range of the noise.

13.2.3 Squawk Box

Crowd dispersal weapon field tested by the British Army in Ireland in 1973. This directional device
emits two ultrasonic frequencies which when mixed in the human ear become intolerable. It
produces giddiness, nausea or fainting. The beam is so small that it can be directed at specific
individuals (Alexander et al., 1996).
There are many reports of dolphins using a similar technique, either when hunting or when
swearing at a human experimenter. In a U.K. radio programme some years ago, a researcher
recounted playing back its own sounds to a dolphin to see what it would do, including listening