ADDERS ARE AFRICA'S DEADLIEST SNAKE
March 17, 2013
last month, I had never seen a puff adder. After two days in South Africa,
I had seen nine. Although this highly venomous viper is shy if unprovoked,
the species is credited with the majority of human deaths from snakes
on the African continent. Apparently some folks have a way of provoking
a professor at Davidson College, and I went to South Africa to collaborate
with colleagues conducting research on vipers and cobras. Our hosts
were Graham Alexander, a professor at Wits University in Johannesburg,
and Xavier Glaudas, who has a postdoctoral position. Xavier was one
of my students at the University of Georgia, conducting studies on pit
vipers - rattlesnakes, cottonmouths and copperheads. He now works with
the even more dangerous puff adder.
reach lengths well over five feet, and the largest ones have a mid-body
diameter approaching that of a football. The head of the largest one
we found was about as wide as my boot.
are typically very secretive and well camouflaged, so hunting for them
is not as easy as it sounds. The reason we found several is because
most of them had radio transmitters in them that allowed us to locate
them in the wild. They had been caught over the previous month, and
the researchers had surgically implanted a transmitter in each one before
releasing it. Xavier is then able to track the snakes' movements on
a daily basis.
project is the first of its kind in Africa. One scientific goal is to
determine how a male puff adder's feeding intake affects reproduction.
The specific research objectives are to find out if well-fed male puff
adders cover more ground in search of receptive females, and if they
win more battles for access to females against other not-so-well-fed
males. Prior to mating, male puff adders, like most pit vipers in North
America, often engage in combat to see which one gets the female. They
don't bite each other. The contest consists of each snake trying to
physically overpower the other in what looks like an arm wrestling contest
(with really big arms; for their length, puff adders are one of the
stoutest large snakes). Presumably snakes that have consumed more prey
than others will be healthier and heavier. They will also presumably
travel longer distances to find females and will win more contests.
But no one knows for sure. The experiment will help scientists better
understand whether enhanced feeding opportunities can decide which male
is more effective at acquiring females.
adder will eat almost any vertebrate that crosses its path, mostly small
mammals, birds, and lizards. I watched with trepidation as Xavier offered
a native mouse to one of his animals as it lay motionless and virtually
invisible beneath a bush. Leaning into the bush he used long tongs to
dangle the already dead prey in front of the snake's mouth to entice
it to eat. In the experiment, he feeds half of the male snakes mice
but leaves the other half to fend for themselves in the natural environment.
Such studies help unravel the endless mysteries about how wild animals
interact with others of their species and what determines whether one
individual is more successful than another.
well-fed experimental puff adders be more successful in mating than
their counterparts that are feeding at the normal rate? The results
of the study will become clear later in the year during the reproductive
season. Xavier is testing the hypothesis that a direct connection exists
between having a few good meals and mating success.
field ecology experiments is a time-consuming process and, with puff
adders, a risky enterprise. But uncovering details about how ecological
systems work is the way we increase our understanding of the natural
world. I was captivated watching these incredibly dangerous yet highly
camouflaged snakes up close in their native habitat. I was also glad
Xavier was the one feeding them the mice.
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