orianne
When
I started working on eastern indigo snakes in Highlands County, Florida, I knew
that finding indigo snakes would not come easily.
The
consensus from people who have looked for or studied indigos in Florida is that
indigo snakes are difficult to survey for in peninsular Florida, even in areas
where are doing relatively well. Part of this difficulty stems from the
tendency of indigo snakes in peninsular Florida to use a variety of shelter
sites and habitats throughout the year, so indigo snakes can be almost anywhere
any time of the year.
Indigo
snakes in peninsular Florida are also not as closely tied to gopher tortoise
burrows during the winter as they are in southern Georgia, where indigo snakes
depend on tortoise burrows for overwintering sites. This weaker association can
make targeted searches around tortoise burrows, a proven technique in south
Georgia, less reliable in Florida. So I was excited when fellow Orianne Society
biologist Dirk Stevenson and his field crew decided to join me and my field tech,
Zach Forsburg, to search for indigo snakes in Highlands County for a week in
late January. We could sure use the extra help and Dirk is one of the best at
finding indigo snakes (and everything else; see Dirk’s blog The Naturalist). And I was not disappointed with our
results.
Enlarge Photo
Searching in an abandoned orange grove
Using
a combination of road cruising and burrow searches we captured four indigo
snakes that week, plus a fifth snake that Zach had caught the week before. Two
of those snakes came from an old field, formerly a citrus grove, whose grassy,
sandy soil was pocketed with tortoise burrows, providing an abundance of
shelter sites. Sure enough, in true south Georgia fashion, Dirk produced two
indigo snakes and two more shed skins from the field. Five indigo snakes in one
week shattered all previous records for indigo snake captures on this project!
At
the close of the week, we had captured 26 indigo snakes in Highlands County since
December 2010 as part of an Orianne Society study to determine how indigo
snakes respond to habitat fragmentation. Thirteen of these 26 snakes have
received surgically implanted radio transmitters and we have been following
these snakes throughout the past thirteen months. Most of these snakes have
come from the Archbold Biological Station, where we have been focusing most of
our search effort during 2011.
Being
familiar with indigo snake radio telemetry in Georgia (having done some myself)
I was very interested to see how these indigo snakes on the southern end of the
Lake Wales Ridge behaved. Indigo snakes in Georgia remain on dry, open
sandhills with an abundance of tortoise burrows during the winter, in order to
use the burrows as overwintering sites.
Once
things warm up in the spring, the indigo snakes begin moving off of the
sandhills and start using a mix of upland habitats, flatwoods, wetlands, and
floodplain forests for foraging and thermoregulation. Some male indigo snakes
in Georgia may move two or miles from their winter sandhills to summer foraging
grounds. Our Highlands County indigo snakes displayed a very different
behavior. Our Florida indigo snakes did not display strong seasonal differences
in movement or habitat use but rather moved back and forth across the same area
(home range) throughout the year. When we estimated the home range size of our
Florida indigo snakes, we found they were still sizable (over 200 acres) but
much smaller than in Georgia (over 900 acres).
With
one successful year behind us, we are excited about continuing our Highlands
County indigo snake research and better understanding how habitat fragmentation
affects these amazing snakes. This new year will see a few shifts in the focus
of our research. We are now focusing our search efforts in suburban habitats
around the Archbold Biological Station which are highly fragmented by roads but
still support indigo snakes. Studying these “suburban snakes” will
give us a better picture of how individual indigo snakes respond to habitat
fragmentation.
We
are also beginning to develop population models, using the data on individual
indigo snakes that we are currently collecting, to determine how indigo snakes
respond to habitat fragmentation at a population level. Understanding how
populations respond to habitat fragmentation allows us to evaluate the ability
of indigo snakes to persist in particular landscape long into the future.
As
more of Florida’s natural habitats become lost or fragmented it is important to
determine where indigo snake populations are most at risk so that their threats
can be mitigated. But we also plan to use these models to determine where
viable populations of indigo snakes can still persist. Knowing if human
disturbed or modified habitats can continue to support viable populations of
indigo snakes could provide a big boost to the conservation of this species in
Florida.
orianne