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NAAMP III Archive - new techniques
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Wildlife Research Center
NAAMP III Archive
- new techniques
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James C. Ball
1083 Jewell Rd.
Milan, MI
email:jball@ford.com
Introduction
There have been anecdotal reports from InterNet Sources (Herpetology Usenet
Group and the Amphibian Decline Listserver) of treefrogs being found in PVC
pipes almost exclusively from Southern states. Unfortunately, there has been
little discussion on the details of using PVC pipes as a method for sampling
treefrogs. Because this technique is potentially a very simple and easy method
to use to sample treefrog populations, I decided to conduct a preliminary study
on the utility of this sampling method for Gray Treefrogs (Hyla versicolor)
in Southern Michigan. In the Spring of 1996 I attempted to trap Gray Treefrogs
from two ponds that contain active choruses of these frogs. The two ponds are
in close proximity to each other and represent one overlapping population of
Gray Treefrogs. One pond is a temporary pond that dries up annually by the middle
of July at the latest. The second pond is a permanent pond adjacent to a meadow.
This pond has no aquatic vegetation other than microscopic plant life typically
associated with ponds. The density of the treefrog population was estimated
using a Call Index Value of 2 established by the Michigan Department of Natural
Resources for their annual Frog and Toad Calling Survey. A Call Index Value
of 2 is described as follows: "Calls of individuals can be distinguished but
there is some overlapping of calls."
Methods and Results:
The pipe traps were made from 2.5 cm i.d. X 39 cm white PVC pipe. Free
standing pipes were taped to wooden stakes (3.5 cm X 1.6 cm X 122 cm) and driven
into the ground so that both ends of the PVC pipe were open to the environment
and the lower opening was about 10 cm above the ground. Six of these pipe traps
were located around the permanent pond about one meter from the water edge and
in standing grasses. The temporary pond had one large willow tree on the bank
and many other smaller trees around its bank. Six pipe traps were tied to the
trees so that the lower open end of the pipe was about 10-30 cm above the ground.
In both cases the PVC pipes were open at both ends.The pipe traps were checked
every other day and especially after a heavy, warm rain that resulted in active
calling by these frogs. I found no frogs of any species in these pipe traps.
The pipes were left in place for an extended period of time beyond the active
breeding season of the Gray Treefrog in our area. The pipes were checked weekly
during this period. The only animals attracted to the pipe traps were jumping
spiders (Salticidae) who made two nests in two of the pipes around the permanent
pond.
Discussion:
Soon after these preliminary studies were completed, a presentation
using a pipe trap method was made at the 1996 SSAR meeting (Domingue O'Neill
, 1996). This report showed that PVC pipes of similar dimensions used above
were effective in trapping Pine Woods Treefrogs (Hyla femoralis) in
North Central Florida. However, there are significant differences between the
two methods. The latter method used drift fence arrays with the PVC pipes driven
into the ground and located at the ends of the fence.
There are a number of possible reasons why using the pipe trap method (open-ended PVC pipes) did not capture any Gray Treefrogs while the use of pipe traps by Domingue O'Neill was very effective in trapping Pine Woods Treefrogs. The most obvious reason is that Gray Treefrogs do not find open-ended PVC pipes a secure refuge from predators. In retrospect it seems possible that Eastern Garter Snakes (Thamnophis sirtalis), which are relatively abundant in my area, could crawl up the open end of the pipe near the ground and predate on any hiding treefrogs. A second possibility is that the treefrogs in this study were not concentrated to the location of the PVC pipe by the use of drift fences. A third possibility is that the diameter of the pipe used in this study is not optimal for Gray Treefrogs. Finally, it is still possible that PVC pipe traps are not an effective method for sampling Gray Treefrogs.
Future Efforts:
One of the key features of using this technique for sampling Gray Treefrogs
resides in its simplicity. Therefore, future efforts will not employ the use
of drift fence arrays which are very manpower intensive to construct. My efforts
for the Spring of 1997 will be directed towards the use of many more PVC pipes
of at least two and possibly three different sizes driven directly into the
ground. In addition, I have located several wetlands with a Call Index of 3
(Full Chorus. Calls are constant, continuous, and overlapping) where I will
locate these pipe traps.
References Cited:
Domingue O'Neill, Elizabeth (1996) "PVC pipe refugia: a sampling method
for studying treefrog biology"; Program Notes & Abstracts; Paper No. 155;
39th Annual Meeting of the Society for the Study of Amphibians and Reptiles,
Univ. of Kansas, Lawrence.
U.S. Department of the Interior
U.S. Geological Survey
Patuxent Wildlife Research Center
Laurel, MD, USA 20708-4038
http://www.pwrc.usgs.gov/naamp3/naamp3.html
Contact: Sam Droege, email: Sam_Droege@usgs.gov
Last Modified: June 2002