Unexpected Findings in Vermont

When I started in on
this Timber Rattlesnake telemetry project last year I had a lot of notions
about what it would be like and the sorts of places the snakes would turn up. 
It’s a good thing I didn’t share these notions with many people in advance, because
I would have been off.  Any book will tell you that Timber Rattlesnakes live in
deciduous forests with high densities of oak and hickory trees, which provide
food for the rodents that Timber Rattlesnakes primarily feed on.  While our
snakes certainly do spend a lot of time in such habitats, we’ve been finding
them in many sorts of places I never would have imagined.  It’s not that the
books and I were wrong; it’s just that there are always new things to learn,
and a certain percent of any population in any species will usually act a
little differently than we think they are supposed to act.

This far north,
rattlesnakes den communally in rocky ledge habitat. We’ve known for a long time
where most of these dens are but what we know very little about is where the
snakes hunt, how far they travel from the dens, and what sort of important
travel corridors they might use. We also want to know how much time they spend
on private and developable land and how many rattlesnakes we actually have. 
Knowing whether or not the population is increasing, declining, or holding
steady will also greatly aid efforts to conserve the species.  Most of what we
knew about the summer range and habits of rattlesnakes in Vermont came from
roadkill specimens, reports from landowners who wanted snakes removed from
their yards, and old bounty records from before 1971.  The Orianne Society, in
cooperation with Vermont Fish & Wildlife and The Nature Conservancy, is
using a method called radio telemetry to help fill in some of these information
gaps.  Through working with the landowners we are now beginning to gain some
insight into what have been long-standing mysteries in the state.  A year into
the project we have identified several tracts of land that are used heavily by
Timber Rattlesnakes that we never would have suspected were all that important
before.  One of these tracts has a variety of habitats on it but what alarmed
me most was which piece of the property the snakes used most; the marsh.

Probably the
biggest surprise so far is how much time our snakes have been spending in
wetlands. This would not be surprising if we were talking about Timber
Rattlesnakes in the southern portion of their range; commonly referred to as
“Canebrakes”, which are often associated with wetland habitat. But in the
northern portion of the range, the use of wetlands by Timber Rattlesnakes was
thought to be uncommon.  A constant source of frustration for me last summer
was the regular routine of hiking a mile over steep and rocky terrain to a
secluded beaver pond, and then trying to figure out — without flooding my
boots — exactly which moss hummock one of our snakes had swum to since the
last time I checked in on him.  After a misplaced step and total
body-submersion – and a $350 repair bill from the folks who make our telemetry
receiver — I stopped tracking that snake to a specific moss hummock in the
wetland. I figured just knowing he was in that wetland somewhere was good
enough.  This year, with a new batch of snakes, the trend of heavy wetland use
has continued.  As of this morning one of our snakes was hunting on a beaver
dam and another was coiled in a foraging position in the middle of a
cedar/sphagnum swamp.  Unless they’ve captured a meal in the last few hours, it
is likely they are still there. Other Timber Rattlesnake researchers have been
learning in recent years that a fraction of their snakes spend time in trees, a
revelation that shocked many people.  With only six snakes tracked last year,
we never observed that sort of behavior, but with another year getting started,
and more snakes being tracked, I keep hoping the next beep that comes out of my
receiver will be coming from above my head.

The fact that our snakes
were turning up in some unusual places was interesting from the start but I
became even more interested in the trend when I began to realize that
individual snakes seemed to have their own unique habitat preferences.  Snakes
observed foraging in a wetland were observed doing it on a regular basis while
others only seemed to pass through as needed.  Another snake stuck mostly to
field edges, one always turned up in beech/sugar maple stands, and two more
must have done some research on the habits of Timber Rattlesnakes and hung out
primarily in oak/hickory hardwoods.  While there is much more to learn on this
front it is clear that Timber Rattlesnakes thrive in ecosystems made up of a
mosaic of habitat types.  Some habitats may be more important than others –
there is no denying that mast-producing oaks and hickory are extremely valuable
to the species – but having differing habitat preferences and a variety of
habitats to choose from makes a population better able to survive changes to
the environment.  This is pure speculation but I have begun to wonder if the
heavy wetland use we have been seeing is a direct result of the historic
wide-spread deforestation in the region.  One hundred and fifty years ago much
of the current Timber Rattlesnake habitat was being used for agriculture and
the only patches left mostly undisturbed might have been wetlands.  If that is
true then the few snakes we had with a strong preference towards wetlands might
have been more successful at spreading their genes into future generations.  It
makes sense but in all honesty we will probably never know. 

Each week we draw closer
to meeting our overall goals and learning enough about the land use patterns of
our snakes to adequately manage the population.  The species is just barely
hanging on in the state and without careful considerations may disappear from
the state entirely.  With every new observation we draw closer to ensuring that
never happens.  In the meantime though, I’m going to keep looking up.