using its strong snout and thickly muscled torso. In the tropics sal-
amanders are scarce, but the soil is churned up by hundreds of
species of legless amphibians, the Apoda (Greek for "legless ones").
Several families of frog are well-equipped excavators, digging with
pointed snout or spadelike feet. In the Malay Archipelago, herps
reach the summit of their locomotor evolution. Here is found the
flying frog. Spreading the thin membranes between its long fin-
gers and toes, the flying frog launches off a forest perch and glides
effortlessly to another tree a hundred yards away. It's not true
Rhacophorus—
Flying Frog of Malaya
MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS | 55
powered flight, like the flapping progression of birds and bats, but
the frog's powerless glide has a certain herp elegance.
All told, in habitats from all climates, the Class Amphibia scores
three-thousand species, just as many as the total number of non-
flying mammals. We're not living in the Age of Mammals, we're
living in the Age of Frogs.
Mammal chauvinists also underestimate turtles. Compared to
frogs and their amphibian kin, turtles don't score high in the spe-
cies competition—only two hundred and thirty species fill the
modern turtle clans—but turtle limbs, necks, backs, and skulls are
true marvels of joint architecture. Most turtles can fold up every-
thing that sticks out from the shell—neck, limbs, tail—and tuck it
into the armored box, leaving little exposed. Several turtle species
go even further in safeguarding their soft parts. Hinge lines have
evolved in the top shell (the carapace) or in the bottom (the plas-
tron) so that after it has pulled in its appendages, the turtle can
close up the neckline and limb apertures, sealing its entire body
into a nearly impregnable strongbox. The basic turtle shell itself is
a most unusual structure that has evolved only through a bizarre
bit of embryological hocus-pocus. Turtle shells have three layers:
(1) the outer horny plates, a tough covering sheathing the bone
beneath, like the horn-core sheaths of bison; (2) the outer bony
plates, which lie just under the horny sheath and grow within the
lower skin layer; and (3) the ribs, which arch around the body and
fuse to the underside of the outer bony plates. Turtle hips and
shoulder bones lie more deeply inside the body, beneath the ribs—
a startling arrangement because in humans and all other verte-
brates the ribs lie beneath the shoulder (reach around and feel your
own ribcage beneath the edge of your shoulder blade if you don't
believe this statement). In order to get the ribs up and on top of
the shoulder, the turtle embryo inside its egg must grow the ribs
much more rapidly than usual, pushing the developing ribcage up
and between the shoulder and hip, and attaching the rib edges to
the underside of the shell bones. No other vertebrate—not even
the tanklike nodosaurian dinosaurs—has ever evolved a mobile body
armor so complete and effective as the turtles'.
Turtle heads also command the respect of bioengineers. Tur-
tle jaw and joints guide the chewing stroke into a long backward
slide of the lower jaw against the upper. Toothless turtle beaks
56 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
and palates are armed with horny cutting edges and multi-toothed
shredding-crushing platforms. This basic masticatory apparatus is
marvelously adaptable. Land tortoises shred tough grass. Giant sea
turtles crush clams. Snapping turtles can slice up a dead trout or a
drowned cow into chunks small enough to swallow. Right now, in
the 1980s, my science is enjoying a turtle renaissance. Paleontol-
ogists in Utah are investigating the muscular-electrical phenomena
of turtle chewing by using sophisticated electromyographs, high-
tech gadgets that chart each muscle's physiological activity. Field
paleontologists at Berkeley are mapping the historical details of
turtle evolution through Cretaceous and Paleocene strata. An em-
inent New York anatomist is completely revising the turtle family
tree. In scientific meetings all over the country the Turtle Renais-
message: Turtles are complex, turtles are successful, turtles are
worthy objects of research.
The total turtle count—two hundred and thirty species—
doesn't seem like an irresistible horde compared to the several
thousand mammals in today's global ecosystem. However, turtles
have scored quite an impressive ecological triumph in one very
important role, that of freshwater predator-omnivore. Gavin Max-
well's Ring of Bright Water is an absolutely charming otters' tale,
the story of these sleek-furred aquatic mammals that frolic in the
Scottish streams, catching salmon and crayfish and stirring up warm
bemusement in human onlookers. All through the Temperate Zone,
otters delight the naturalist and the lay public. But how many other
freshwater, semi-aquatic mammal predators can you name? Mink,
of course. Relatives of otters on one hand, land weasels on the
other, mink do hunt in streams. How many others? If you caught
the excellent BBC series "Life on Earth," you saw footage of the
swimming shrew, the Desman of the Pyrenees, a molelike furball
that dives for aquatic worms and other freshwater small fry. Our
own New England star-nosed mole goes hunting in water, using
its starburst-shaped snout tip to feel out wriggling prey. Andean
streams flowing through Peru are host to the fish-spearing mouse,
Ichthyomys, that impales prey on its projecting front teeth. But if
we go to a tropical lake or sluggish river, is it full of otters, mink,
and paddling shrews? No, it is full of turtles. The mass of tropical
turtledom far exceeds the Mammalia in numbers of species in the
MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS
57
aquatic-predator category. A few tropical otters do exist, and
Uganda can boast of the giant otter shrew (a full two pounds in
weight), but a single Congolese river system can display a dozen
and a half specialized turtles, swimming after prey, eating fallen
fruit and leaves, walking along the river bottom, scavenging pieces
of hippo carcass.
The entire subject of aquatic predation should embarrass the
mammal chauvinist into silence. The lion may be king of the beasts
on land, the top link in the terrestrial food chain. But in the Nile
waters and in the great Rift Valley lakes of East Africa, the lion
must fear for its crown. Here the king is the Nile crocodile. Con-
trary to the popular view, crocodiles are neither sluggish, nor stu-
pid, nor lacking in maternal affection. Crocodile mothers guard their
nest with aggressive vigilance for the three-month incubation nec-
essary for hatching. When the hatchlings chirp as they struggle to
wrest free of the shell, the mother will gently help her newborn,
lifting them in her jaws from nest to water's edge. For months a
fter
hatching, the young crocodiles stay close to mother in the shal-
lows, where she can drive away any potential threat. Field zoolo-
gists in Georgia and Florida tell the same story of maternal care
of our Mississippi alligator. (Alligators and crocodilians differ in
shape only in minor features, the broader, flatter snout of the 'ga-
tor being the most obvious; the term "crocodilian" encompasses
all 'gators and crocodiles and their fish-eating kin, the frying-pan-
headed gavial.)
The Harvard professor's close call with the South Sea croco-
dile is a warning that even the numero uno on nature's scale must
be careful around crocodilians. Crocodiles are good hunters. An
adult male will stick to one hunting territory for years, learning all
the ins and outs of the watery passages among the reeds, gradually
developing an ambush style calculated on the seasonal flux of fish,
snails, turtles, and land mammals that come to the water's edge to
drink. Adult crocodilians watch the shoreline, their heads sub-
merged except for the bulging eyes and nostrils. If an antelope
ventures close enough, the croc glides smoothly through the water,
propelled by its deep, sculling tail. Five or six feet from the ante-
tilian jaws clamp shut on furry snout or leg. The thrashing victim
is dragged under the water and stunned as the croc whirls around,
58 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
rolling over and over. Sometimes a mammal victim escapes after
one of its legs has been wrenched out of its socket. Lions, chee-
tahs, and baby elephants have died this way. Not only Man but his
domestic servants can be croc prey. A giant South Seas croc snagged
a horse from an Australian farmyard and dragged it back to the
billibog.
Although such furry big game are key elements of many big-
croc diets, most of the crocodilian clan subsist on less dramatic
fare—fish of all kinds, aquatic turtles, swimming snakes, freshwa-
ter mollusks. When just out of the egg, young 'gators and crocs
hunt aquatic insects, frogs, and other humble game. Everywhere
in tropical waterways the crocodilian ensemble—two dozen spe-
cies—are by far the most important large semi-aquatic predators.
All crocodilians are large by modern reptilian standards. None are
as small as a Scottish otter, but adult size does vary from species
to species. Giants among living species are the slender-snouted
gavial of the Ganges and the estuarine crocodile of the Pacific
shores. In both, a big male can exceed twenty feet in length and
half a ton in weight. Tiniest are the heavily armored West African
dwarf crocodiles and dwarf caimans of South America. In one dwarf
species, females probably breed at the tender young length of two
and a half feet. But these dwarfs make up for their size with ar-
mor. All crocs have bony plates, sheathed in horn, embedded in
the deep skin layer, and in dwarfs the plates make an especially
tight-fitting mosaic, a flexible cuirass for chest and back. What's
this protection for? Tigers and jaguars do pounce on careless little
crocodilians caught basking on the shore, but the chief hunters of
any given crocodilian species are other crocodilians.
Ecological science, for reasons not clear to me, lacks the lyric
eloquence of geology. Ecological terms rarely have the color or
dynamism of such geologisms as "rift," "thrust fault," "mountain-
building revolution," "hogback." Ecology tends rather toward the
gray-flannel-suit metaphors of marketplace and commerce: "re-
source partitioning," "energy budgets," and "investment." But
modern ecological theory has given us one quite lovely term—the
"guild." The clockmakers' guild in sixteenth-century Basle pro-
tected the interests of all the makers of timepieces in that Swiss
Protestant city. Guild councils enforced quality control and regu-
lated the entry of new artisans into the urban market. An ecolog-
MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS
59
ical guild is all the species that follow a particular way of making
a living in local habitats. Hence the top-predator guild of the Ser-
engeti is filled today by lion and leopard, cheetah and spotted hyena.
Working the same landscape is the small-predator-scavenging guild,
the golden jackal, black-backed jackal, Egyptian vulture, and grif-
fon vulture. Reviewing our ecological census figures, we would be
compelled to conclude that most tropical guilds are dominated by
the "cold blooded" clans. In the small semi-aquatic guild of pred-
ators, turtles are masters. The large-predator aquatic guild is firmly
in the hands of a crocodilian cartel.
I would hope that by now in our census through the verte-
brate guilds the delusions of mammal superiority would be shaken.
But we are not even half done. Remember, all the world's non-
flying mammals add up to 3,000 species. There are now, by con-
servative estimate, 3,000 lizard species and 2,700 of snakes.
European culture and its American offspring are more igno-
rant about lizards than about any other great divisions in the "cold-
blooded" clans. Lizards don't abound in the cities of the Temper-
ate Zone that served as cradles for Western science. Heidelberg,
Paris, London, New Haven—all are great university towns, but all
languish in a state of lizard impoverishment. Go to school in one
of the Ivy League Colleges, take a field ecology course, and you
will count yourself lucky to catch a glimpse of a little brown skink,
speeding along a sunlit pathway. Turtles, frogs, salamanders, and
snakes all outnumber lizard species in upper New York State or
Massachusetts. Too bad, because the natural economy in the spe-
cies-rich tropical world supports a dazzling lacertilian display.
"Lacertilian," the standard label for all lizards, comes directly
from the Latin lacerta, the Roman name for the common Mediter-
ranean wall lizard, a hefty four-pounder that has hunted big in-
sects around human habitation since the Parthenon was built, and
before. (Spanish conquistadors called the broad-snouted crocodil-
ian of the Mississippi el lacerto—a label that quickly degenerated
into "alligator.") Travel south from the Mediterranean wall lizard
country, past the sandy barrier of the Sahara, and you will reach a
lacertilian evolutionary epicenter. Patrolling along the shorefront
of the Nile are six-foot monitor lizards, long-tailed hunters that
can swim, dig up croc nests with their strong foreclaws, and race
off to escape predators by climbing a tree or descending a burrow.
60 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
Locomotor triple threats, nearly all the dozens of monitor lizards
can make quick progress in all modes, arboreal, terrestrial, and
aquatic. Farther from water are snub-nosed savannah monitors, the
lacertilian equivalent of badgers, truculent, stout-shouldered dig-
gers that can exploit the buried resources of eggs, rodents, an
d
fossorial reptiles.
Whenever I see a stocky golden-skinned savannah monitor, I
get a lump in my throat and misty eyes—memories of a wonderful
sweet-tempered pet I had my second year as a graduate student.
Part of the task for my thesis was to measure metabolism during
walking in lizards, so we could calculate an ecological energy bud-
get for dinosaurs. After three frustrating months of failed experi-
ments with skinks, race runners, and desert iguanas, I reluctantly
concluded that even though it was small-brained, the average liz-
ard was smart enough and mean enough not to consent to walking
on a treadmill for an hour while wearing a lizard-size gas mask with
two hoses attached to a great big Beckman oxygen analyzer with
a battery of blinking lights emitting clicking instrument noises. But
then I acquired G. Hawn, the gold-colored monitor. She ran
beautifully, and we got excellent data. And she was a quick learner.
We had to run the lizards when their stomachs were empty, be-
cause digestive metabolism complicates the measurements of ex-
ercise. G. Hawn learned that she would be fed two plump white
mice, alive and fresh, and a raw egg at the end of a successful run.
She soon was giving us two good long runs each week. Alas, she
succumbed suddenly to a respiratory infection, untreatable be-
cause lacertilian veterinary medicine is still very crude. No mam-
mal chauvinist can tell me that lizards can't be clever. I can't claim
that my monitor responded to me with affection, but her viva-
cious character certainly elicited that response from her owner.
Both Nile monitor and savannah monitor are snail-boppers, a
prey especially attractive to lizards. Adult lizards from the two
species go about with swollen acorn-shaped teeth, pestles that can
crack even the most resistant-shelled mollusks. Such evolutionary
enthusiasm for shellfish might seem surprising, but in fact tropical
habitats of all climates offer a tempting menu of multi-species es-
cargot, because snails are among the most diverse of the land and
aquatic animals. Although not many lacertilians are specialized
swimmers—unlike their distant scaly relatives, the turtles and croc-
MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS I 61
Dragon lizards, past and present. Today Komodo Dragons reach nine feet