Venomous Serpents - Tracks and Shadows: Field Biology as Art - page 119

Some cobras upped the confrontational ante by evolving spitting, once in Asia and
perhaps twice in Africa. Spitters have round discharge orifices above the fang tip and
eject venom streams for six feet or more, prior to which they track an antagonist's head
movements and accurately aim for its eyes. 19 Being squirted causes intense pain and,
if not treated, blindness. A long-popular theory was that trampling ungulates promp-
ted the evolution of spitting, but in fact herds don't exist in Southeast Asia and spitters
arose prior to their advent in Africa. More likely players would have been well armed
and had forward-facing eyes, such as swiping, sharp-clawed carnivores and bipedal,
tool-using primates—so, keeping in mind reports of capuchins killing a terciopelo with
branches and Old World monkeys standing to peer at snakes, and having seen video of
a chimp shaking vines and a stick at an approaching python, 20 I'll bet the only long-dis-
tance weaponry among all serpents evolved at least partly in response to our anthropoid
brethren.
In Australia, it's as if advanced snakes were told to start over, but strictly as cobra
relatives and with little competition from other lineages. More than a hundred species
of elapids in the Land Down Under encompass brown snakes that look disarmingly like
New World coachwhips and also eat frogs and lizards; black mamba-like coastal taipans
that likewise feed on mammals and readily attack their enemies; coralsnake-like bandy-
bandies that specialize on blindsnakes as prey; and other examples of convergent evol-
ution. Seven species of stout-bodied, wide-headed death adders are remarkably similar
to vipers in body shape and behavior, even equipped with slightly mobile fangs and dis-
tinctively colored tails with which they lure prey. Australian elapids also spawned two
invasions of the sea, including a few species of eel-eating sea-kraits, which lay eggs
back on land, and several dozen species of seasnakes with diverse diets, all viviparous
and so specialized for swimming that they can scarcely move out of water. 21
Atractaspididae (Greek, atraktos, a thin shaft or arrow, and aspis, a viper) comprises
about seventy-five species of African and Middle Eastern serpents. All are burrowers,
almost all of them rear-fanged and feeding on centipedes or secretive reptiles (quill-
snouted snakes eat only worm-lizards), though one relative of African centipede-eaters
lacks rear fangs and eats earthworms. Two species of harlequin snakes, however, so
closely resemble coralsnakes in having fixed front fangs, colorful writhing defensive dis-
plays, and a diet of limbless reptiles that they were long classified as elapids. Likewise,
some dozen species of folding-front-fanged stiletto snakes were once referred to the
Viperidae, but their maxillary bones rotate on ball-and-socket joints rather than hinges,
such that they stab sideways and backwards with one fang or the other at nestling mam-
mals—and are impossible to hold without being bitten! Front fangs thus evolved once
or twice within this small, geographically restricted group, convergent on those of the
other two more speciose, dangerously venomous snake lineages. 22
Advanced snakes that aren't viperids, elapids, or atractaspidids formerly were
lumped in Colubridae (Latin, coluber, a serpent), whereas now that name is restricted
to about seven hundred mostly harmless species, such as the European smooth snake,
African egg-eaters, and North American ratsnakes, as well as the rear-fanged brown
treesnake and deadly boomslang. Among those no longer called colubrids, most of them
venomous and some nearly front-fanged, are hog-nosed snakes and roughly seven hun-
dred neotropical species assigned to Dipsadidae (Greek, dipsas, a serpent whose bite
causes thirst), along with just over two hundred North American gartersnakes and their