In the fall of 1998 Mindy Thompson (one of my graduate students) and I put up a drift fence completely encircling a pond at Bath (we had help from some of my other grad students, Michelle Balk, and Marlo Swaldo).  The fence acts as a barrier to the movement of salamanders and other amphibians, and together with pitfall traps made from 5 gallon buckets, allows us to uniquely mark each individual entering the pond to breed.   We also recapture them on their way out of the pond after the breeding season is over.  This simple technique lets us monitor fundamental aspects of the population dynamics of amphibians in the pond, including breeding population size, annual mortality and birth rates, individual growth rates and breeding frequency.  There are surprisingly few studies of this kind, yet they are an indispensible source of data for evaluating important problems like the proposed global amphibian decline.  If you want to learn more about how scientists are monitoring amphibian populations, visit DAPTF for a good introduction on the web.

Here's how the drift fence works...

an amphibian encounters the fence on approaching the pond	turning left or right, eventually the individual falls into a pitfall trap	the captured salamander awaits our arrival the next morning
retrieved, captured animals are returned to our lab for processing	processing involves weighing, measuring, determining sex, and giving each individual a unique identifying mark

Comparative Physiology of Paedomorphic and Metamorphic Salamanders
Effects of Clearcutting on Amphibians