BACKGROUND INFORMATION
Drift fences are often used to collect, survey, and monitor amphibians
and reptiles. Students at Davidson College have used drift fences to
gain a better understanding of the reptiles and amphibians present in
the area. During the spring of 1999, students at Davidson College constructed
a series of drift fences (about 1000 feet in all) in the forest in the
northern part of what is now the Davidson
College Ecological Preserve. These fences are usually opened (trapping
animals) during the Spring and Fall of each year. When opened, they are
run daily by students working in the Herpetology Laboratory.
HOW DOES A DRIFT
FENCE WORK?
A drift fence is essentially a wall that most reptiles and amphibians
cannot jump or climb over. The "wall" is usually a couple
feet in height and can be as long as the area you wish to study.
When critters move through the forest, the fence forces them to crawl
along it, seeking an opening. Along the length of the fence, we
installed 5-gallon buckets flush with the ground. As an animal tries
to find a way around the fence, it falls into one of the pitfalls from
which it cannot escape. Since many snakes can easily escape from
a bucket, funnel traps are also placed along the fence. The funnel
traps allow snakes to enter them. However, once inside the trap,
no exit is readily apparent to them.
WHAT HAPPENS NEXT?
Student
volunteers check the drift fence on a daily basis to monitor for herps.
Daily monitoring is essential in order to prevent dehydration of captured
animals. In addition, captured amphibians or reptiles are more vulnerable
to predation in the bucket so it is important to minimize this problem.
After each amphibian or reptile is marked or recorded, it is released
in the direction it was heading before it encountered "the wall."
PALM PILOT DATA ENTRY
In the fall of 2001 Mike Dorcas and student J.D. Willson developed a data
entry program that allows the drift fence worker to use a Palm Pilot to
enter data gathered while running the drift fence. The Palm uses Pendragon
Forms 3.1 software to allow a variety of capture and climatic data to
be entered into the hand-held computer in the field. The Palm is then
synched with the lab computer and all the data is automatically entered
in a database. Using this new technology has greatly reduced the amount
of equipment that students must bring with them in the field while running
the drift fence and eliminates time and and possibility for error associated
with manual data entry.
Drift fences are fairly permanent structures and allow for long-term, intensive monitoring of reptiles and amphibians. One drift fence at the Savannah River Ecology Lab in South Carolina has been in operation for more than 20 years! This particular fence has allowed scientists to better understand these somewhat elusive creatures and their role in the local ecosystem.
