‘SPECIALISED SIDEWIN
SIDEWINDERS
DERS
travel with CONSIDERABLE SPEED ,
leaving a characteristic series of separate, parallel,
J - SHAPED TRACKS.’
quite bewildering! Despite the impression that the
creature is throwing loops of its body in all directions,
sidewinding actually involves a highly-complex
locomotory pattern in which sections of the body are
alternatively lifted, moved forward and then set down.
During any sequence, the body is in static contact with
the ground at just two points. Sidewinding can occur in a
left- or right-handed manner and leaves a characteristic
series of separate, parallel, J-shaped tracks, each
orientated at an angle to the direction of travel. The tracks
are about as long as the snake’s body.
attaining forward velocities of 2.0 total lengths per
second. Increased velocity can be achieved by using
sidewinding on sand, and sidewinders have been shown
to switch from pure lateral undulations, to lateral undula-
tions with sidewinding, and then to pure sidewinding,
with incremental increases in speed.
But sidewinding is not confined to desert-dwelling
snakes, and is also utilised effectively by other species to
traverse slippery substrates, such as slick, slimy mudflats
(e.g. the Dog-faced Water Snake, Cerberus rynchops). In
fact, sidewinding can be induced in many snakes,
Sidewinding is exemplified by the snake whose common although they are often reluctant to do so. Not only is
name alludes to its preferred method of locomotion: the
sidewinding adaptive for travelling on yielding or
Sidewinder (Crotalus cerastes). By varying the propor-
slippery surfaces, but by preventing slippage at points of
tion of its body that is in contact with the sand, this small, contact, it confers energetic advantages relative to all
venomous pit viper can ascend steep, sandy dunes
other forms of snake locomotion.
without slipping – a feat that related pit vipers cannot
accomplish. Other desert snakes that often use sidewind- Concertina locomotion involves the anterior region of the
ing include Asian and African vipers, Horned Adders
body remaining stationary while the posterior end is
(Bitis caudalis) and Peringuey's Adder (Bitis peringueyi). drawn up behind it in a series of tight curves. The poste-
Specialised sidewinders travel with considerable speed,
rior end then provides a region of static contact, enabling