For many people, finding a rattlesnake in the yard does not
present much of a dilemma. They just kill it. But, for those people that
appreciate rattlesnakes and don’t want to kill them all, encountering one of
these venomous animals near the house raises an important question: What now?
A
rattlesnake around the house is a risk that most people just don’t want to
take. And, that’s understandable. Inevitably, the topic of relocation is raised
as a humane alternative to killing the animal, which is likely just traveling
through or was attracted to an abundance of rodents. But, a letter from a
reader summarizes a common concern.
.jpg) |
| A Timber Rattlesnake Relocated by Gary L. |
“I live in northeast Alabama outside of Scottsboro at the
base of a small mountain ridge. A rocky ravine runs down the mountain
right to my backyard. When I walk out of my back door I am automatically
herping (i.e. finding a lot of amphibians
and reptiles). Occasionally a timber rattler will show up.
Since I have several small dogs and don’t want the snakes so close to the
house, I relocate them. I have a good set of tongs and snake bag and can
relatively safely handle the snakes. Initially I took the snakes to a
secluded area about 5 miles away. My conscience started to bother me
because I knew that the snakes would not be able to return to their proven den
site. Since then I have taken several snakes a short distance backup to
the top of the mountain ridge and, I’m sure, in range of their den. Now
I’m concerned about the snakes being able to find their way back to my
backyard. My question is: ‘Is it a death sentence for the snake if I move
it far enough away from its range that it cannot get back to its den?’
Thanks,
Gary L.
Alabama”
As
Gary notes, rattlesnakes do not just spend their lives randomly crawling across
the landscape. Timber Rattlesnakes
(Crotalus horridus) often use den sites
throughout their lives. The use of these dens isn’t just a matter of
convenience; the rocky and underground caverns are necessary for the snakes to
survive the winter in colder climates. These areas provide protection from the
cold and from predators. In the fall, females will give birth around their dens
and the young benefit from the security of the rocks and also from having a lot
of adult rattlesnakes around.
Timber
Rattlesnakes do sometimes disperse from their “home” den and reach other dens
to mingle with new snakes, but the point is that there are often unique
features of the landscape that are necessary for a snake to survive and these
features are well-known by individual snakes that spend their lives in the same
general area.
So,
as you might expect, relocating a rattlesnake away from your house isn’t
automatically a humane option at all, it may just be dooming that snake to die
a slow death in the woods as it crawls around looking for something familiar.
One
short-term option is to relocate snakes only a short distance from your house,
perhaps less than 1000 feet (roughly 300 m). This technique moves the snake
away from your home but allows the animal to stay within the forest it knows
and close enough to its den that it can easily return. As Gary noted, this
means that the snake very well could wander back to the house (even if this is
unlikely).
However, most
people that go through the trouble of catching and relocating a rattlesnake want a
more permanent solution and are interested in moving a snake far enough that it
won’t try to return. I’ve written extensively about how living with
rattlesnakes is an inseparable part of living in rattlesnake country and the most
ecologically-minded (and safest) plan of action when co-existing with
rattlesnakes is to take appropriate precautions (like teaching children and
dogs about potentially dangerous animals). Similarly, I never advocate capturing a venomous snake
because it is a dangerous activity and runs a high risk of snakebite. I’m going
to assume that you know all this but, for whatever reason, you have decided it
is still important to move a rattlesnake away from the house.
To
give a relocated snake the best chance of surviving, it should be moved to an
area that already has a population of the same species. This is a sure-fire way of
knowing that the area is appropriate and the relocated animal can fulfill all of their
needs there, which include the ability to find prey, refuge, and mates. If you don’t know for
sure that an area has a rattlesnake population, look for habitats that are similar to the area around your home. For Timber Rattlesnakes on the east
coast, good habitats would include deciduous forests, ideally with some rocky
slopes and mountains. The same is true for another venomous species that shares this habitat, the Copperhead (Agkistrodon contortrix).
Even
when a rattlesnake is moved to a perfect habitat with a resident rattlesnake
population, it will still go through an adjustment period. A study conducted in
the early 1990’s radio-tracked a number of Timber Rattlesnakes in Pennsylvania
to compare behavioral differences between snakes that had always lived in a
particular area versus snakes that had been relocated to that area (the relocated
snakes had been captured from areas 5-107 miles [8-172 km] away from their new
home). I’ll let the original authors (citation at the bottom of this post)
describe the take-home message of the study:
“Our results clearly
indicate that long-distance geographic translocation (i.e., relocation) results in decreased survival and an alteration
of the behavior of C. horridus. Specifically,
translocated snakes made frequent and extensive movements. The pattern of
movements suggested either the snakes were searching for familiar environmental
features, or they were exploring the new territory in order to become familiar
with the existing conditions. Translocated snakes suffered from higher rates of
overwintering mortality, predation, and disease than did residents. Only four
snakes out of 11 (36.7%) are known to have survived through two complete active
seasons following translocation.”
This
isn’t meant to be all doom and gloom. The authors note that their relocated
snakes were able to find denning sites, even if they did die over the winter in
higher proportions than resident snakes. In addition, relocated snakes that did
survive the first year or so or life in their new home gradually started to
exhibit behavior more similar to resident animals. This means that they started
to move around less, and shorter movements reduce a rattlesnake’s risk of being
found and eaten by a predator (or run over by a car). The authors further note
that young snakes may have an easier time adjusting to a new area than the
adult snakes that they had moved around.
A
smaller-scale study conducted in South Carolina had slightly more encouraging
news. Of four Timber Rattlesnakes relocated from their capture location, none
tried to return to their original home and only one had died after a couple of
years, when the study concluded. The animals in South Carolina may have fared
relatively well because in the southeastern United States, Timber Rattlesnakes
do not seem to rely as much on specific denning sites that are used year after
year. This may mean southern snakes are more adaptable to changing conditions
but more research with more snakes is needed before this can be said with
confidence.
On
a very large scale, when confronted with news that an entire Timber Rattlesnake
den was going to be destroyed by some highway development in Kansas, a dedicated group of researchers undertook an intensive effort to identify a new suitable home for the snakes that lived there. These researchers looked for new potential sites with limestone
caverns (for winter refuge and denning sites) surrounded by large areas of
grasslands and fields (Timber Rattlesnakes out west tend to use different habitats
than on the east coast) and lots of small mammals to eat. They even made sure
that there were appropriate basking areas that faced the sun in the right
direction. Finally, and perhaps most importantly, the new habitat would have to
be away from too many humans. They found one site that met all of their
criteria and moved 29 rattlesnakes from the doomed highway den to this new site.
After a couple years of monitoring, it looks like their homework paid off
and the relocated rattlesnakes are generally making themselves at home.
So,
is relocating a rattlesnake away from its original habitat a death sentence?
Not necessarily. By carefully choosing an appropriate and suitable relocation
site, you can give a rattlesnake a reasonable chance of surviving in a new
home. Even in seemingly excellent habitats though, relocated rattlesnakes often
have a difficult time adjusting and experience a relatively high risk of dying from disease, predators, or exposure.
This
post is focused primarily on Timber Rattlesnakes and the habitats they use, but
the same general concepts are true for all snakes. If you want to
move a snake away from your home and give it a good chance of surviving, you
must give a lot of thought to that snake’s needs and ensure that the new home
meets these needs. If you have a snake you want to relocate and you're not sure what to do, you can ask me.
Want to Learn More? Check Out These Articles:
M.
L. Walker, J. A. Dorr, R. J. Benjamin, & G. R. Pisani (2009). Successful
relocation of a threatened suburban population of timber rattlesnakes (Crotalus
horridus): combining snake ecology, politics, and education IRCF Reptiles and Amphibians,
16 (4), 210-221
Nowak,
E.M., Hare, T, & McNally, J (2002). Management of ‘‘nuisance’’ vipers:
effects of translocation on western dia- mondback rattlesnakes (Crotalus
atrox). Biology of the
Vipers, 533-560
J.
R. Mohr (2010). Autoecology of the timber rattlesnake (Crotalus horridus) in
the South Carolina mountains Dissertation,
Clemson University
Reinert,
H., & Rupert, R. (1999). Impacts of Translocation on Behavior and Survival
of Timber Rattlesnakes, Crotalus horridus Journal of Herpetology, 33 (1) DOI: 10.2307/1565542
Sealy,
J. (1997). Short-distance translocations of timber rattlesnakes in a North
Carolina state park: a successful conservation and management program. Sonoran Herpetologist,
10, 94-99
No comments:
Post a Comment