Recent
Research
Georgia
Hellbender Surveys
and Effects of Landscape and Land Use Patterns on Abundance
Project
Leader: Jeff Humphries,
Ph.D., Independent Biologist, Clemson, SC
Collaborators:
Kate Mitchell, Institute of Ecology, University of Georgia;
Megan Goddard, Ph.D., Clemson
University, Forestry and Natural Resources; also thanks to assistance from
Zach Felix, Dr. Michael Freake, Shannan Miller, Kelly Overduijn, Scott
Stavely, and Dave Steen
Project funded by:
Georgia Department of Natural Resources, Wildlife Resources Division
Project
Overview:
Where do
hellbenders live? How many are out there? What factors influence where
hellbender still exist? Though relatively simple questions, the answers
are fundamental to the establishment of efforts to protect this species.
Georgia lies at the southern extent of the hellbender's range, but there
are quite a few healthy mountain streams in the state and hellbenders are
historically known from 21 of them (some of the records date back to the
1950s).
We set out to
answer several questions during this project:
-
Do
hellbenders still exist at the sites that once had hellbenders?
-
What
is the relative abundance of hellbenders in Georgia's streams? That
is, are hellbenders more abundant in some streams than others?
-
What
are the landscape and land use patterns that affect the hellbender's
distribution and relative abundance?
We surveyed all of
the sites using a combination of snorkeling and rock turning, where one
person would lift rocks and the other would look beneath rocks and feel
for hellbenders. This worked very well... if a hellbender was there, we
are very certain that we detected it.
Surveying for hellbenders in north Georgia, May 2005.
Left to right: Shannan Miller, Jeff Humphries, Kate Mitchell, Dave Steen,
and Kelly Overduijn
We captured 62
hellbenders during this study and capture rates ranged from 0 - 2.6
hellbenders per person hour (adjusted to number of people searching). The
most hellbenders we found during one survey was 13. We referred to streams
as "healthy" if our capture rates were above 0.5 hellbenders per
hour. In healthy streams, hellbender habitat was relatively continuous
whereas marginal sites consisted of small stretches of decent habitat with
long stretches of heavily silted areas. Check out the following map for
our statewide results.
Shaded triangles
represent healthy sites, open triangles represent marginal sites, and
circles represent streams where hellbenders were not found. The major
watersheds of the Tennessee drainage are also shown. Notice that
the best hellbender streams are surrounded by National Forest land (shaded areas).
Hellbenders were
found in 69 % (13 out of 21) of the historic sites. "Healthy"
populations only existed in 43 % of the streams we surveyed. Here are a
few examples of healthy and marginal sites.
 |
 |
| A healthy hellbender stream. We caught 13
hellbenders here with little effort. This stream's watershed is
almost entirely forested and within the Chattahoochee National
Forest.
|
A marginal hellbender hellbender stream.
We managed to turn up 2 hellbenders over many hours of searching.
Erosion (because of poor land use) has resulted in smothering of
most of the large rocks and a simplified stream (the rapids are
gone).
|
The amount of forest
surrounding a stream, coupled with elevation, were the best predictors of
hellbender abundance. So, it turns out that high elevation, heavily
forested watersheds contained the best hellbender streams in Georgia. But
we also found that lower elevation and lower gradient streams could
support good hellbender populations as long as those watersheds were also
heavily forested. The problem is that most of the lower elevation land in
the Georgia mountains has been converted to agriculture and we found
streams surrounded by agriculture tended to be heavily silted -- the
hellbender habitat was pretty much gone. Here's a graph of hellbender
abundance (square-root transformed) in streams with various degrees of surrounding agricultural
land.
Much of the higher
elevation watersheds are public National Forest Service land. So,
hellbenders are now restricted to high elevation, protected areas and
populations are almost completely isolated from each other because of land
clearing at lower elevations. This is probably the case throughout the
hellbender's range...
What can be done to
make sure hellbenders remain in Georgia's streams in the future? A lot of
the damage is already done to a lot of the lower elevation streams in the
state, but hellbenders tend to occur in the headwaters of many of those
streams. Besides the continued protection of National Forests, its
important that we try to protect or restore forested land at low
elevations. Development along many of the streams in north Georgia may
ultimately be the biggest future threat facing hellbenders.
But enough bad
news... here are a few photos of the hellbenders we caught!
A fairly large adult caught at one of the best streams in Georgia.
One of the many young hellbenders we caught. Its
really
good to see small hellbenders in Georgia's streams.
Copyright 2006. This site
developed and maintained by Jeff Humphries.
If you have questions or comments, please send an email to jeff@hellbenders.org.
