Biology Reference
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climate cycles isolated their cloud forest homelands, yielding still more varieties. Fin-
ally, about three million years ago, lowland eyelash palm-pitvipers dispersed into South
America with the emergence of the Panamanian landbridge. 7 Today those snakes chal-
lenge us to adopt the respectful caution of forest dwellers and behave less like care-
less intruders. The odd nuance of a mossy patch, idly scrutinized during a lunch break,
may reveal catlike pupils surrounded by green coils; among several bright flowers, one
might unfurl, suspended by a prehensile tail, and flash an open-mouthed threat display.
Could it be otherwise, I wondered, in our australopithecine birthplace?
African bush vipers also evolved during fragmentation of tropical forests, including
those of the Eastern Arc Mountains of Kenya and Tanzania, and parallel their Neotrop-
ical analogs in several respects. Green bush vipers come in yellow and orange, like eye-
lash palm-pitvipers, and both gape at predators. 8 But up close and personal, would ar-
boreal Old World serpents remind me of those I knew firsthand in Latin America? Their
homeland is the least studied large landmass biologically, even as its habitats dwindle
under human impact, and this heartbreaking dilemma was obvious during our trip. We
found only six live snakes, whereas Charles Pitman, in his 1974 A Guide to the Snakes
of Uganda, described the country as “plentifully serpent stocked.” 9 Pitman even said
Great Lakes bush vipers were abundant in papyrus stands, but for days on end I found
no snakes there or anywhere else. Finally one morning we picked up a pregnant rhino-
ceros adder, her skin resplendent in black, greens, blues, and reds, body as big around
as a grapefruit—surely among the most lavishly patterned and stoutest of all serpents.
Someone had stoned her to death.
My high point came a few nights later, after an hour sloshing in and out of shallow
swamp pools, peering upward and sweeping a light over vegetation, looking for the
opalescent reflection of snake bellies. Frogs, frogs, and more frogs . . . then even as I
muttered “Huh?” my headlamp beam snapped back over its path through the foliage
and telltale coils materialized in a sapling ten feet above me. Catching venomous snakes
in trees can be tricky, so I took a deep breath and looked off into the darkness for a few
What would be the smart way to do this?
I made a crude platform of fallen branches, climbed onto it without disturbing my
quarry, and looked up to make sure the serpent couldn't fall on my face. Then I delic-
ately grasped the juvenile green bush viper with three-foot-long snake tongs, without
disrupting its resting posture, and lowered my prize into a cloth snakebag. After a sigh
of relief I called out, “Bob, just got my number one goal in Africa!” And as if that weren't
enough, the little bush viper gained luster during a photography session the next after-
noon when I noticed its open-mouth display differed in some particulars from that of
palm-pitvipers. The newly captured animal extended its head with fangs erect when my
camera lens came close, whereas New World species cock their necks back with front
teeth folded when they confront predators. 10
There was another surprise among the few snakes we caught. Nocturnal serpents
usually have subdued markings and hide when inactive, but we discovered a thirty-inch,
velvety green Dipsadoboa with catlike pupils that prowls streams at night and sleeps on
foliage by day. It had a frog in its stomach. Perhaps at cool elevations the leaf-colored
Bwindi snake must bask even as it sleeps to ensure warm body temperatures for digest-
ing bulky prey, thus requiring a camouflage unsuited to relatives in the warmer low-
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