STUDIES CAN REVEAL UNUSUAL PHENOMENA
plant and animal species in the world has secrets, and scientists who
explore the intricate and intimate details of their private lives help
solve ecological mysteries. J.D. Willson, a faculty member at the University
of Arkansas, told me of an amazing biological observation about a little
his doctoral work with the University of Georgias Savannah River
Ecology Lab. He conducted his research on the Savannah River Site in
Aiken and worked on a project involving the capture of more than 3,000
snakes. Most of them were black swamp snakes.
secretive, seldom-seen aquatic creatures weigh in at less than 1/10th
the size of the big watersnakes familiar to anglers and kayakers. Most
herpetologists who have spent a lifetime working with reptiles have
never seen a live one because they are uncommon in most areas throughout
their geographic range.
snakes have a name that belies their beauty. The back and sides are
glossy black. The belly is brilliant red and can only be seen when the
snake is turned onto its back. These inoffensive animals do not bite
people, and even if they did, they are too small for it to matter. The
largest one ever found was a little over a foot and a half long. Their
prey includes leeches, small salamanders, tadpoles, and tiny fish. Swamp
snakes remain in the water or mucky sediments almost their entire life
and if not kept moist will quickly die.
his colleagues capture aquatic snakes with a simple technique: minnow
traps. These are small plastic cylinders with a funnel at each end that
let fish, salamanders, and snakes enter, assuming they are small enough
to do so. The traps are set with the top above water so that air-breathing
animals like snakes do not drown in them. During sampling, J.D. sets
450 to 600 traps each day at one of his collecting sites. Although some
of the animals may escape through one of the funnel openings, large
numbers are trapped and then captured when the researcher checks the
traps the next day.
a snake, J.D. uses a special branding technique that is not harmful
to the snake. It gives each individual a unique identification code.
The mark allows the individual to be recognized years later. Capture-recapture
studies, as they are known, are used with many animals to determine
how long they live, what their movement patterns are, and how fast they
to SREL in the summers to continue his long-term studies on this fascinating
little species of snake, and this summer he observed an amazing occurrence.
Six years earlier he had captured two male black swamp snakes on the
same day. He marked them for future identification after recording the
usual information: length, weight, and where they were caught. During
his summer sampling this year, he caught the same two snakes again.
marked individuals is not unusual. In fact, of the 3,069 black swamp
snakes he has captured, 1,506 had been marked since he began the study
in 2003. He has recaptured 529 of these at least once. But these two
recaptured individuals were different. He caught them on the same day,
and neither snake had been seen since their first capture on the same
day six years earlier! The odds of each being seen only twice, each
time on the same day, are extraordinarily high.
two snakes were recaptured on the same day after an interval of six
years remains a mystery. Was it coincidence or are there as-yet-unexplained
behavioral and ecological phenomena in operation? Continued study and
comparisons with the timing of when other marked snakes are recaptured
relative to each other may turn out to be revealing whether the
answer is simple coincidence or scientific phenomenon. The black swamp
snake is just one of the species that scientists study in an ongoing
effort to understand natures myriad and marvelous secrets.
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