the open on the forest floor or are visible on leaves and
branches, usually a short distance from the ground. They
are a good subject for the axiom “look but do not touch.”
There are about 30 species in the genus Dendrobates
and five in the genus Phyllobates. All contain toxic
alkaloids in their skin secretions. Each of these
diminutive frogs is characterized by bold, often striped
patterns of orange, red, yellow, blue, or green that glow
like neon against a dark background. The Chocó tribes
of western Colombia use toxic alkaloid compounds
called batrachotoxins (a word that literally means “frog
poisons”) extracted from the frogs’ skins as a potent
arrow poison. One species, aptly named Phyllobates
terribilis, is reputed to be potentially lethal to the
touch. So don’t touch it. The others offer less risk, but
you probably shouldn’t touch them either. A selection
of poison- dart frogs appears in plates 11- 21– 24. Wow.
Skin toxicity and bright coloration are evolutionarily
linked. Poison- dart frogs represent a case of aposematic
(or warning) coloration. Bright, bold patterning serves
as a signal to potential predators that they should avoid
the animal; it is a signal that they presumably either
remember or have become innately attuned to recognize.
After all, if a predator such as a bird (and birds see colors
very well) were to eat the frog, sure, the predator would
suffer from the frog toxin. But the frog would likely be
killed by the would- be predator— not good for the frog.
So there is a strong correlation between toxicity and frog
obviousness. It is not an accident that frog obviousness
takes the form of very bright, easy to remember colors.
Almost 300 noxious or toxic alkaloids have been isolated
from various species of amphibians. Batrachotoxins are
considered to be the most toxic of the various alkaloid
compounds (alkaloids are discussed further later in this
chapter). The precursors of batrachotoxins are obtained
in the insect diets of frogs, particularly from ants.
Frogs kept in captivity show reduced levels of toxicity,
suggesting that certain components of their natural diet
are required to synthesize the skin toxins.
For a bit more on poison- dart frogs see chapter 16.
Brightly Banded Snakes: Some of These Can
Kill You, Some Are OK
Neotropical coral snakes (54 species) are boldly
patterned and colorful animals that are extremely
venomous (plate 11- 25). Coral snakes tend to be
nonaggressive unless threatened (it is wise not to push
this envelope). Why do they have such bright banding
Plate 11- 26. This is a nonvenomous Honduran milk snake
(Lampropeltis triangulum hondurensis). Many species of snakes
in the tropics closely resemble coral snakes. Photo by James
Adams.Plate 11- 25. This is a coral snake, highly venomous. Photo by
James Adams.Plate 11- 27. Many coral snakes have a pattern in which red
bands touch yellow, indicating that they can “kill a fellow.” This
snake has that pattern. But it is a nonvenomous False Coral
Snake (Erythrolamprus mimus). It is not fully clear whether
it mimics coral snakes, they mimic it, or neither (though if
neither, it would indeed be a striking coincidence). Photo by
Dennis Paulson.186 chapter 11 evolutionary arms races: more coevolution, more complexity