Tuesday, September 4, 2012

Readers Write In: Now This is a Rattlesnake

  It must be snake season, based on the number of identification requests I'm receiving lately. At least when it comes to rattlesnakes, that makes sense. In the southeastern United States, rattlesnakes tend to mate in the late summer and fall. During this time, it's more likely to find a big male rattlesnake cruising through your yard or crossing the road as they look for females. Just ask Anne.

"Subject: Info please


I live in Georgia and just shot this snake a few minutes ago.  Can you please identify it for me?  Since I didn't want to get too close, it appears to have 10-12 rattles.  Also, is it possible to ID a male vs. female?

Thank you so much and I hope you are having a nice Labor Day.



   I was happy to inform Anne that the snake she found was a Timber Rattlesnake, Crotalus horridus, a large, venomous species found throughout the eastern and central United States. In colder climates, Timber Rattlesnakes den together in large groups during the winter, often in rocky areas. In the spring, they'll emerge and search for things like squirrels and rats to eat. The species has become very rare in the northeastern United States but it is still hanging on in Georgia.

   It's hard to see a big beautiful snake killed, so, in answering Anne, I told her that I hoped she hadn't killed it for no good reason. She responded, "Thank you so much for the information concerning the Timber Rattlesnake.  I would never kill a snake that was in the woods, minding his own business. As I was walking to the mailbox, this snake became aggressive." 

  Although the safest course of action when encountering a venomous snake is to head in the other direction, I can understand wanting to get rid of a large venomous snake around the home. That's why I created this brochure, which I provided to Anne.

  Determining whether this rattlesnake is a male or female is a little trickier. Male lizards and snakes have paired reproductive organs called hemipenes (singular: hemipenis). These structures are internal (except during mating) and best imagined as pockets. By inserting a small probe into a snake's cloaca (the opening that has both excretory and reproductive functions), you can determine if there are hemipenes. Basically, if the probe goes in relatively far, you know that you're within the pocket of a hemipenis. This is the method that I use when conducting a snake study because it's important be accurate.

   Using a probe is a sure-fire way of determining a snake's sex. However, there are ways to guess. Male rattlesnakes fight for breeding opportunities. These fights are usually won by the larger animal. As a result, bigger males tend to have a greater chance of passing on their genes. As a result and over time, male rattlesnakes became larger, on average, than females (who don't normally engage in combat). So, if you find a very big rattlesnake, there's a good chance it's a male. Edit: Melissa Amarello notes (in the comments) that another theory explaining this difference in size suggests females stop growing after they become sexually active while males keep getting bigger. Another way to sex snakes is by looking at the tail. Because male tails contain hemipenes, they are usually bulkier and longer than those of females.

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