NEWS 115
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Coral snakes don't live in the sea at all.Quite to the contrary,they are exclusively
terrestrial. They received their name on account of the coral-red rings around
their bodies. There are coral snakes that are lethally venomous, others whose
bite is mildly venomous but extremely painful, and yet others whose bite is
completely harmless. The roughly 75 species are not all closely related but
resemble one another in appearance. This is termed mimicry. The well-known
German expert Robert Mertens asked as long ago as 1958 who was actually
imitating whom. Since then the special mimicry in coral snakes has been
known as Mertensian mimicry.
Coral snakes
by Frank Schäfer
Snakes
Coral snakes indicate whether they are venomous. In the venomous species red follows yellow, in the
non-venomous red follows black.This is the non-venomous
Lampropeltis triangulum campbelli.
An example of classic Batesian mimicry from
the native European fauna. Above: a
venomous wasp. Below: a totally harmless
hoverfly. All photos: F. Schäfer
imicry - a strange word, don't you
think? It may not have been
invented by him, but it was introduced
into general use in zoology by Henry
Walter B
ATES
in 1862. It is derived from the
English word mimic, meaning to copy or
emulate. B
ATES
studied insects and
discovered mimicry in Amazonian
butterflies, among which he found
M
extremely similar species that weren't
closely related to one another at all. One of
them tasted dreadful and was avoided by
predators such as birds, etc. The other
profited from this in that a bird that had
once eaten a horrible-tasting butterfly
would never try one again.
But you don't need to travel to the Tropics
to observe this sort of thing. Here in Europe
there are insects that are known to be
totally harmless - the hoverflies (Syrphidae)
- and are very successfully camouflaged as
wasps or bees. Wasps and bees deliver
painful stings, but are otherwise harmless.
Here too the inexperienced animal rapidly
learns when something is best left alone.
And the hoverflies benefit thereby.
This obvious form of mimicry is named
Batesian mimicry, after Henry Walter B
ATES
.
Not the case in coral snakes
But M
ERTENS
discovered that Batesian
mimicry couldn't apply in the case of the
coral snakes, as any creature bitten by the
extremely venomous members of the
genera
Micrurus
or
Micruroides
doesn't
survive the experience. Hence species that
resemble these extremely venomous coral
snake genera cannot benefit from the bad
experiences of potential predators! M
ERTENS
deduced from this that the moderately
venomous snakes of the genera
Erythrolamprus
,
Plicocercus
,
Rhinobothryum
and
Scaphiodontophis
must have invented
the "coral-snake pattern" consisting of
black, red, and yellow or white rings. The
bite of these genera doesn't kill the
predator but generally causes it pain. The
fact that an animal that had had a bad
experience of this kind would in future
avoid similar-looking species benefits not
only the extremely venomous species, but
also the completely harmless king snakes
of the genus
Lampropeltis
!
Still under discussion
Mertensian mimicry remains the subject of
discussion among experts to the present
day, without any truly conclusive result.
Against the hypothesis put forward by
M
ERTENS
is the fact that species specialized
in feeding on snakes - this is termed
ophiophagy - don't seem to care much
whether the species in question is
venomous or not. In the distribution region
