Chapter

How to Count Snakes—and Other Things

James Lazell

in Island

Published by University of California Press

Published in print January 2005 | ISBN: 9780520243521
Published online March 2012 | e-ISBN: 9780520931596 | DOI: http://dx.doi.org/10.1525/california/9780520243521.003.0008
How to Count Snakes—and Other Things

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All of the species on Guana Island have to produce more offspring than needed to maintain stable populations, or they would become extinct. Population biology begins with the question “What is N, the total number of individuals in the population?” Unfortunately, for snakes, one cannot use the shepherd's simple formula: count the legs, and divide by four. Determine the N at one point in time. Then try to learn if N changes with time. It might do so seasonally or cyclically from year to year or decade to decade, or it may be in long-term flux leading to stability at some higher number or to zero. The best viable way to determine N, the population size, is to count all the individuals present at one time. If one cannot count the whole population, one may be able to count the number in a known area, for instance 100m, and extrapolate to the population's total range.

Keywords: population; species; biology; flux; stability

Chapter.  16198 words.  Illustrated.

Subjects: Animal Pathology and Diseases

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