|
1-6 of 6 messages
|
Page 1 of 1
|
|
Road systems a factor in diversity in Timbers?
|
Reply
|
|
by ChuckHurd on February 25, 2010
|
Mail this to a friend!
|
http://www.conservationmaven.com/frontpage/snakes-interrupted-roads-causing-genetic-decline.html
For wildlife like the timber rattlesnsake, trying to cross even light-traffic country roads presents a formidable life-or-death challenge. As a new study in the journal Conservation Biology shows, these roads can also contribute to the genetic decline of the species.
This can occur when roads cut off the path of movement of individuals leading to isolated groups that are unable to reproduce together. This in turn causes a reduction in genetic flow across the population.
To examine this issue in the timber rattlesnake, Rulon Clark and fellow researchers conducted genetic sampling of individuals within two types of forested areas in upstate New York - one fragmented by several low-traffic roads and the other road-free.
They found that genetic diversity was lower in the areas with roads - likely because reproduction had been occurring among smaller pools of individuals. Further, snakes in areas with roads had undergone greater extent of genetic differentiation indicating a reduction in gene flow as isolated groups of snakes went down their own distinct trajectories of genetic change.
These findings bode ill for the snake and other wildlife undergoing a similar phenomenon. High genetic diversity and flow are important for maintaining healthy populations capable of adapting to environmental stressors.
The study provides evidence that roads are at least partly to blame. The researchers conducted a landscape genetic analysis to compare where pairings between snakes would occur in the absence of disturbance versus what was actually recorded. They found that roads acted as major barrier to genetic connectivity.
This makes sense for the timber rattlesnake based on past behavioral studies. The authors write,
"In an experimental study, Andrews and Gibbons (2005) demonstrated that timber rattlesnakes cross roads slowly (approximately 10 cm/s) and individuals stop moving and remain immobile for up to a minute or more in response to any traffic noise. From their behavioral data, they estimated that timber rattlesnakes crossing roads would suffer an 80% mortality rate on roads with a traffic volume of 3,000 cars/day, a traffic level corresponding to the minor roads in our study."
This high mortality level, along with plain avoidance of roads, likely plays a key role in the observed genetic decline. Given the findings, the authors recommend that measures such as the construction of culverts be undertaken to minimize the impacts to the snakes. They note however that more research is needed to determine whether these measurers will actually have a beneficial effect on restoring genetic connectivity.
--Reviewed by Rob Goldstein
CLARK, R., BROWN, W., STECHERT, R., & ZAMUDIO, K. (2010). Roads, Interrupted Dispersal, and Genetic Diversity in Timber Rattlesnakes Conservation Biology DOI: 10.1111/j.1523-1739.2009.01439.x
|
| |
|
RE: Road systems a factor in diversity in Timbers?
|
Reply
|
|
by Crotalusssp on February 25, 2010
|
Mail this to a friend!
|
|
Interesting article, but not surprising at all. Fragmented populations are great candidates for evolution to occur in.
|
| |
|
RE: Road systems a factor in diversity in Timbers?
|
Reply
|
|
by Cro on February 26, 2010
|
Mail this to a friend!
|
Very good article.
No doubt that timber rattlesnakes that travel back and forth from dens to summer areas are often killed by cars.
There are a couple of roads in north Georgia that are particularly bad about this happening.
I am not sure that culverts or tunnels under the roads would be used. Perhaps, if there were drift fences of some sort along the roads to direct the snakes to the culvert pipes, it could work.
But, without a fence of some sort, the snake will likely take the most direct route, and cross the road exactly where he comes out of the woods.
Best Regards
John Z
|
| |
|
RE: Road systems a factor in diversity in Timbers?
|
Reply
|
|
by ChuckHurd on February 27, 2010
|
Mail this to a friend!
|
|
The problem is more advanced then just crossing the road. As you old school snake hunters know, the roads are where to catch snakes. At sun up, roads heat up faster then the surrounding and at sun down they hold heat longer then the surrounding. This is a magnet to snakes. They are not just crosses the roads, they lay on them to bask. That is their fatal mistake. Even if we provide them with a safe crossing point, they are still gona come out to grab that extra heat. I do not see a solution. Educating the public so they will not make extra efforts to hit them is about all we can do, but many of us have been doing that for decades and thus far, we are not getting the best results.
|
| |
|
RE: Road systems a factor in diversity in Timbers?
|
Reply
|
|
by tj on February 27, 2010
|
Mail this to a friend!
|
"As you old school snake hunters know, the roads are where to catch snakes. At sun up, roads heat up faster then the surrounding and at sun down they hold heat longer then the surrounding. This is a magnet to snakes. They are not just crosses the roads, they lay on them to bask."
It's not too much of a problem in NY. Timber's rarely, if ever, bask on roads here. It's kind of interesting. I've only heard of one or two tim's being found on a road and they were found crossing. They never seem to bask anywhere here. There was a phenomenon a few years back where a bunch of timber's were basking at a rest stop. But, they never crossed the highway and the state shut the rest area down. So, all was well with that. That's why NYer's don't road cruise at night...there's never anything out...aside from frogs, toads, turtles, and salamanders (when it's migration time). I've only ever found ONE snake on a road. It was a milk snake, mid afternoon, out in the country trying to get acrossed.
Anyhoo, that was a good article, thanks for sharing. Hope you're feeling better, BTW.
-TJP
|
| |
|
Email Subscription
You are not subscribed to this topic.
Subscribe!
My Subscriptions
Subscriptions Help
Check our help page for help using
, or send questions, comments, or suggestions to the
Manager.
|
