Biology Reference
In-Depth Information
gists had long ridiculed claims that constrictors break their victims' bones, anacondas,
it turns out, do just that. As for causes of mortality, mammals, caimans, and bigger
anacondas take juveniles, whereas large females succumb to disease, overheating, and
injuries from prey. One perished with a turtle wedged in her throat, and another was
fatally impaled by the catfish she swallowed. 28
Jesús's team also documented the giant water boa's mating aggregations, each of
which consists of several yards of writhing coils and looks like a cornucopic Medusa
heaped up in the shallows. A dozen or so smaller suitors entwine along an enormous,
loosely coiled or stretched-out female for up to forty-six days, during which they stroke
her body with pelvic spurs and struggle with their hind parts to father her offspring. All
indications are that this is as complex as it looks, and through it all females seemingly
control whom they let in, maximizing reproductive success by choosing one or more of
the best males. Obviously we still have much to learn about snake social systems!
Just as birth certificates and bank records don't adequately describe us, statistics on
reproduction and diet fall short of fully revealing other animals' natural history. What
is it like to be a giant snake? Reticulated pythons and green anacondas resemble their
close relatives in many ways besides ancient constricting behavior, so perhaps vignettes
of other pythons and boas can help us envision lifestyles of the big and famous. African
pythons, for example, eat vervet monkeys, who in turn adopt vigilant postures and give
specific alarm cries at the sight of one—yet they react to python tracks with curiosity
and jump back only when they find the large snakes themselves in the grass. When bio-
logists interrupted a ten-foot Madagascan ground boa constricting a Coquerel's sifaka
and freed the lemur, they noted that she had enlarged nipples and refused to leave the
vicinity, then saw a bulge in the snake's foreparts, presumably her baby. And as with
anacondas, things don't always go well for other big serpents; a sixteen-foot Asian rock
python died when a ninety-pound hog deer with fifteen-inch antlers lodged in its gul-
let. 29
Turning to a widespread relative of anacondas, boa constrictors are superbly cam-
ouflaged in habitats ranging from Mexican thorn scrub to Amazonian rainforest. The
intricately repetitious colors of one I found at La Selva were nearly indistinguishable
from the creases, splotches, and curves of its woody basking site. These eclectic hunters
ambush lizards, birds, rats, deer, even ocelots and anteaters. One Panamanian individu-
al moved among mammal burrows every few days, waiting for their occupants' return,
and another in Surinam caught three cock-of-the-rock males at a courtship site, the
birds' numbered leg bands later showing up in the snake's droppings. A Costa Rican
boa killed a white-faced capuchin while its comrades screamed and threw sticks; the
snake hissed and struck but didn't abandon the dead monkey. And a Peruvian five-footer
seized a subadult black-chested moustached tamarin from low on a tree in which it fed,
whereupon a male and female bit the captor's head and neck while four others vocal-
ized. The victim escaped and licked its wounds when the snake retreated into a hole,
and its group avoided that tree for a couple of days, then fed higher when they returned.
Of course, all is not “kill or be killed.” A six-foot common tree boa lay draped over a li-
ana in Peru, her symmetrical coils a cryptic patchwork of browns and yellows in the sun-
flecked rainforest understory, her chunky head oddly doglike. For hours, a smaller male
flicked his tongue up and down the female's neck while vibrating pelvic spurs against
her skin, then coiled nearby, after which they lowered hind parts and he wrapped his tail
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