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How to visually SEX a rattlesnake...

Posted: January 22nd, 2015, 6:39 pm
by John Delgado
...without popping the hemipenis.

Sorry about the thread title :shock: had to get your attention somehow ;)

As you may know ... I am very much a greenhorn to field herping ... My specific interests are rattlesnakes in Northern California.

Who am I? -- You've seen the thread of my first year of rattlesnake field herping http://www.fieldherpforum.com/forum/vie ... =2&t=20724

The 2015 season is around the corner and I am JONESING real bad to get back out there... BUT -- Before the season starts, I want to have a clear understanding of how to effectively determine the sex of a rattlesnake WITHOUT popping the hemipenis. I don't find it necessary to pop the hemipenis, I'm just an amateur field herper.

Please post pics and video if you have them -- Please school me.

Here is a video of one rattlesnake I am pretty sure is female -- In the video I explain why etc. But, am I right ? am I wrong???

There are good close-ups of the tail most of the way through...

...but you can fast forward to 3:40 if you want - where I explain why I think this is a female.


Re: How to SEX a rattlesnake...

Posted: January 22nd, 2015, 8:15 pm
by nhherp
Its really a matter of looking at enough specimens and learning comparitive perspective. Its easier to learn using WDB's and Red D's as the tail banding serves to create a readily visual count method to measure by.
. More bands=longer tail which has greater likely hood of being a male.
This method it's fairly accurate however there is still those ones who are not quite long enough, but a little to short. ..

I responded from my phone and couldn't get video to play smooth but it looked like a male . Long floppy tail.
-N-

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 4:52 am
by The Jake-Man
With timber rattlesnakes, gender can be determined through a subcaudal scale count. 21 or more subcaudals, and there's somewhere around a 95% chance that the snake is a male.

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 9:38 am
by umop apisdn
In my experience, the number of subcaudals can be fairly reliable (as you mentioned, with some margin of error), but the cut-off can vary from one site to another.

Seeing animals side-by-side is helpful, but an opportunity that's often not available.

Body condition can sometimes be an indicator, at least here on the east coast. Since they're all breeding and birthing in fall here, gravid females usually look pretty chunky spring/summer, especially towards the posterior. I've noticed male EDBs tend to have a more squared-off shape to the center ridge down the back, while females tend to be a little more V-shaped. Might also be pure coincidence, but I found that males actively courting females tended to be a bit more yellow.

Because of the high cost of reproduction, males typically outgrow females. However, human-caused mortality usually catches up with most older individuals, but outliers exist.

During the breeding season, if you find a snake on the move, there's a much higher likelihood you're looking at a male.

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 11:35 am
by Stohlgren
Some of these methods (counting subcaudal scales) involve actual getting the specimens in hand. You mention you are new to field herping (and even if you are not), it is best to keep a hands off approach. You also need to make sure you are within the law of the area you are snake hunting as handling or harassing may not be legal. With enough experience you can get a pretty good guess at sex by looking at tail length. The reliability of this probably varies with species, however.
umop apisdn wrote:Because of the high cost of reproduction, males typically outgrow females. However, human-caused mortality usually catches up with most older individuals, but outliers exist.
Is the cost of reproduction really the reason for males outgrowing females? In many (most? all?) species of snake without male combat, such as natracines, the females outgrow the males.

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 4:33 pm
by Brendan
It's a male. Tail is way too long and thick for a female and like hellerii and cerberus the males are usually larger and darker in color.

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 6:42 pm
by Bryan Hamilton
After a while you can sex most adults by looking at relative tail length. Subcaudal counts and bands are other ways to sex rattlesnakes, but if you really want to know, you need to probe for hemipenes. I'm pretty skeptical of visual sex assignment. I still regularly misclassify sex for small adults. In other words I guess based on looking then check my guess by probing. Juveniles don't have much sexual dimorphism in tail length. And it is possibly to misclassify genders with probing so its not perfect either.
Stohlgren wrote:Is the cost of reproduction really the reason for males outgrowing females? In many (most? all?) species of snake without male combat, such as natracines, the females outgrow the males.
That's an interesting point but there are gender specific pressures. In the species I work with (lutosus) females grow very little in length once they reach sexual maturity. All their extra energy goes to reproduction. They are kind of like balloons that inflate and deflate. Males get bigger so they can win fights with other males. For females, more food mean more offspring via more reproductive events. For males more food means winning more fights and having access to mate with more females. There are some other things to consider like prey availability due to gape limitations. Females never get big enough to feed on pack rats and chipmunks while males do. Once the males reach a certain size, an additional, higher quality prey is available that can increase their growth rates quite a bit.

edtt: I agree with the others that the snake in the video is a male. Females have stubby short tails.

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 8:53 pm
by John Delgado
I appreciate the reply's fellow herpers -- Please keep them coming ... I have much to learn.
nhherp wrote:Its really a matter of looking at enough specimens and learning comparitive perspective. Its easier to learn using WDB's and Red D's as the tail banding serves to create a readily visual count method to measure by.
I wish I had that luxury here in NorCal with the C. o. oreganus

Them WDBs and RDBs are 4 tail bands = female amd 3 tail bands = male -- correct?
The Jake-Man wrote:With timber rattlesnakes, gender can be determined through a subcaudal scale count. 21 or more subcaudals, and there's somewhere around a 95% chance that the snake is a male.
Does counting subcudals work with C. o. oreganus? -- I do research on-line and I haven't seen anything that would lead to that. And is why I am asking here on FHF -- I figure who better to ask than field herpers and/or herpetologists.
umop apisdn wrote:
Body condition can sometimes be an indicator, at least here on the east coast. Since they're all breeding and birthing in fall here, gravid females usually look pretty chunky spring/summer, especially towards the posterior. I've noticed male EDBs tend to have a more squared-off shape to the center ridge down the back, while females tend to be a little more V-shaped.
I have some pics of what you are indicating ... (square back and V-back) I'll post them soon. Please take a look at the vid (below) and see the V-back. Is this a male or female?
Stohlgren wrote:Some of these methods (counting subcaudal scales) involve actual getting the specimens in hand. You mention you are new to field herping (and even if you are not), it is best to keep a hands off approach. You also need to make sure you are within the law of the area you are snake hunting as handling or harassing may not be legal.
I don't have a problem handling the rattlesnakes, if I do have to ever pop the hemipenes I will learn to tube the rattlesnake first. However, I am not in a position to "have to" know without doubt... I'm only a green amateur. Handling rattlesnakes here is no license required. My interest this year however are the in-situ observations. Therefore visual determination of sex is what I am interested in... and I understand that the method is not 100%
Bryan Hamilton wrote: After a while you can sex most adults by looking at relative tail length. Subcaudal counts and bands are other ways to sex rattlesnakes, but if you really want to know, you need to probe for hemipenes. I'm pretty skeptical of visual sex assignment. I still regularly misclassify sex for small adults. In other words I guess based on looking then check my guess by probing. Juveniles don't have much sexual dimorphism in tail length. And it is possibly to misclassify genders with probing so its not perfect either.
Stohlgren wrote:Is the cost of reproduction really the reason for males outgrowing females? In many (most? all?) species of snake without male combat, such as natracines, the females outgrow the males.
That's an interesting point but there are gender specific pressures. In the species I work with (lutosus) females grow very little in length once they reach sexual maturity. All their extra energy goes to reproduction. They are kind of like balloons that inflate and deflate. Males get bigger so they can win fights with other males. For females, more food mean more offspring via more reproductive events. For males more food means winning more fights and having access to mate with more females. There are some other things to consider like prey availability due to gape limitations. Females never get big enough to feed on pack rats and chipmunks while males do. Once the males reach a certain size, an additional, higher quality prey is available that can increase their growth rates quite a bit.

edtt: I agree with the others that the snake in the video is a male. Females have stubby short tails.
Great post -- thank you.

You guys have wayyy more experience that I -- And I don't question experience. However, I want to clarify something. The rattler in the first vid "Betty" - That's a long floppy tail. I'm thinking that rattler was old and malnourished. I've seen some big'ole fat rattlers up here compared to that one. So ... Betty might be a Benny?

Please have a look at this next rattler -- what do you think?

The beginning is good close-up -- And please advance video to 6:05 where I have close-up focus on the tail and my thoughts. Please correct me if I am wrong. I am okay with constructive criticism. I appreciate it very much -- thank you.


Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 8:53 pm
by Stohlgren
Bryan Hamilton wrote:That's an interesting point but there are gender specific pressures.
I guess that is kind of my point. Females aren't smaller solely due to the cost of reproduction, or female snakes of all species would reach smaller sizes than males. There are also pressures that cause males to be larger, such as the need to complete for mates. Or in your example, larger prey size. In the example of natracines, larger females can have more young and despite the cost of reproduction, females reach larger sizes than the males do.

Re: How to SEX a rattlesnake...

Posted: January 23rd, 2015, 9:52 pm
by Bryan Hamilton
Stohlgren wrote: Females aren't smaller solely due to the cost of reproduction, or female snakes of all species would reach smaller sizes than males. There are also pressures that cause males to be larger, such as the need to complete for mates. Or in your example, larger prey size. In the example of natracines, larger females can have more young and despite the cost of reproduction, females reach larger sizes than the males do.
I'm not trying to generalize to all snakes but for rattlesnakes, it's pretty well established that reproductive costs limit the size of females. My guess is that female natricines devote a smaller proportion of energy to reproduction than rattlesnakes.

Given the similarities in female reproduction between vipers and naticines, its interesting how different their life histories are.

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 8:51 am
by Bryan Hamilton
John, I think you're right. That snake is a male. I would correct your logic though. Males have long, fat tails. Females have short, stubby, skinny tails. The tail holds the hemipenes in the males and that's why their tails are fatter than females.

Cool snake and nice video!

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 12:40 pm
by John Delgado
Okay -- Here are the two rattlers from above video respective.

Please tell me Boy? or Girl? -- And why. School me ... please teach me, I am a green sponge.

First 2 pics are from the first video above -- A rattler my wife and I named "Betty"

ImageDSC_0731 by johnedelgado, on Flickr

ImageDSC_0535 by johnedelgado, on Flickr

And the next 2 pics are from the 2'nd video above.

A rattler I named Yogi -- Is Yogi a boy ? or a girl ? A yogi or a Yolanda ??? :lol:

Please tell me why you think either boy or girl... I appreciate your expertise.

ImageDSC_0265 by johnedelgado, on Flickr

ImageDSC_0392 by johnedelgado, on Flickr

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 2:42 pm
by Kfen
I havent worked with that species before, but my guess is both males because of tail length in proportion to rest of body. As someone else mentioned, its not a perfect way to sex rattlesnakes and mistakes can be made by the most seasoned herpers/researchers. Some of them are just difficult to tell.

You mentioned popping. Popping becomes less reliable the bigger the snakes get, working best on neonates and yearlings. You can also cause harm to the snakes when done incorrectly.

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 3:01 pm
by Bryan Hamilton
They look like males to me as well. Again, a long thick tail for males versus a stubby, skinny tail for females. I'll try to post some pictures. One thing I've noticed from looking at pictures is that females have a hard time folding their tail back on their bodies.

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 3:52 pm
by John Delgado
I agree -- Re: exposing the hemipenes -- I am NOT in position to 'have to' do that. I have a great desire to be able to determine the sex of a Northen Pacific Rattlesnake - Crotalus oreganus oreganus. I am understood that visualy sexing a rattlesnake is; 1. NOT 100% and 2. Is difficult.

I have a great adoration and respect for what my wife and I call 'our cornucopia of rattlesnakes' -- We have found a treasure trove location. We have no doubt we will be seeing many of our favorites time and time again. We give them names and refer to them like children.

I'd like to be correct in a hight percentage, and I'd like to be able to effectively determine with confidence in visual terms, explaining in my future videos why I think this or that particular rattlesnake is male or female.

Please post pics and if anyone has video -- please, by all means ... this thread is a class for all to participate and learn.

I'll look up more pics of my 2014 Season rattlesnakes ... if you have pics and/or video ... post'em if you got'em :)

This is Henry -- Is this absolutely stunning critter a Henry or ... a Henrietta ???

Sorry about exposure -- I hadn't yet got used to the new camera ... Nikon D80

ImageDSC_0118 by johnedelgado, on Flickr

ImageDSC_0143 by johnedelgado, on Flickr

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 4:43 pm
by Bryan Hamilton
Henry is a (He)nry for sure. That is a textbook long tail.

Here is a picture of a female lutosus. See how stubby her tail is?

Image

Image

Now here are a couple males for comparison. See how the tail can fold back on the body?

Image

Image

Re: How to SEX a rattlesnake...

Posted: January 24th, 2015, 8:45 pm
by John Delgado
Them pics of lutosus are impressive...!

I have never seen a C. o. oreganus with a tail like your female lutosus. All my rattlers have tails like Betty and Henry and Yogi. Most of them were more beefy like Yogi and Henry ... and some were like Betty, long even taper and not much meat on them.

I have pics and video od 13 rattlers; 1 from 2013, and 12 from 2014 -- And not a one of them have a tail like your lutosus female.

Perhaps I have yet to find a female oreganus from my area...? -- Think of the odds of that happening.

Question: Is your female, at time of that pic ... was she gravid?

Re: How to SEX a rattlesnake...

Posted: January 25th, 2015, 11:59 am
by The Real Snake Man
It is my assumption that the female lutosus is indeed gravid, and that the picture was merely intended to show the comparative lengths of the tail.

Re: How to SEX a rattlesnake...

Posted: January 25th, 2015, 10:02 pm
by John Delgado
Nice job friends -- GREAT info.

Have a look at this one -- Named this one 'Travis'

Sample of what I found on-line...,

From: http://en.wikipedia.org/wiki/Rattlesnake
One of the differentiating features of males and females is the males have thicker and longer tails (because they contain the inverted hemipenes). Also, the tails of males taper gradually from the body, whereas the tails of females narrow abruptly at the vent.

From: http://animals.pawnation.com/difference ... -7294.html
Male rattlesnakes have longer tails than females do. But this is a subjective criterion: It takes considerable experience to distinguish the differences in tail length of rattlesnakes. Male rattlesnakes grow to larger sizes than females do, but this is a valid criterion for judging the gender of mature snakes.

From: http://exoticpets.about.com/od/snakes/q ... snakes.htm
Since the sex organs are held internally, sexing visually is difficult, but there are visible clues. Because of the presence of the hemipenes, these visual clues relate to the shape and lenght of the tail:
•Male: tail thicker and longer than in females, and also tapers less evenly to the tip (thicker for a bit then suddenly thinning).
•Females: tail thinner and shorter than in males, and tapers smoothly, evenly and more quickly.

This one is easy - for a greenhorn like me -- I say Travis is a male :)

Enjoy the vid -- This rattler is absolutely stunning...! -- And look's that big'ole FAT tail ... BEEFY summa'gun...!

Every time me and the wife go by where I found Travis -- We yell "Travis ... Traaaaaviiiiiiisssss... where are you Travis...???" :lol:


Re: How to SEX a rattlesnake...

Posted: January 25th, 2015, 10:40 pm
by VanAR
Complete aside the sexing discussion:
Bryan Hamilton wrote:
Stohlgren wrote: Females aren't smaller solely due to the cost of reproduction, or female snakes of all species would reach smaller sizes than males. There are also pressures that cause males to be larger, such as the need to complete for mates. Or in your example, larger prey size. In the example of natracines, larger females can have more young and despite the cost of reproduction, females reach larger sizes than the males do.
I'm not trying to generalize to all snakes but for rattlesnakes, it's pretty well established that reproductive costs limit the size of females. My guess is that female natricines devote a smaller proportion of energy to reproduction than rattlesnakes.

Given the similarities in female reproduction between vipers and naticines, its interesting how different their life histories are.
The problem with the hypothesis that combat drives large male SSD is that it only explains why there is selection on males to grow large. It doesn't explain why females don't grow as large as females, nor does it explain why males grow larger than females- the ability of a male to outcompete another male for a female doesn't affect female body size at all. The energetic limitation hypothesis is an attempt to explain why males might grow larger than females in conditions where energy is limiting and male reproductive effort is (presumably) less than that of females, where reproductive effort is defined as the proportion of the energy budget allocated to reproduction. Also- it's interesting that some Vipera and some pythons have combat and small-male SSD.

The hypothesis that large-female SSD is driven by selection on females to maximize reproductive output and an absence of selection on males for combat ability has similar problems explaining all circumstances. There are probably many different selective pressures and environmental constraints that might lead to SSD, and the tough part is distinguishing plastic responses from evolved differences.

Re: How to visually SEX a rattlesnake...

Posted: January 26th, 2015, 7:13 pm
by AndyO'Connor
Travis is a male. To your question of "what are the chances I've only seen males?"... It's pretty high if you are finding them at a time of year when males are moving around looking for food and females, whereas females are sitting in a quiet safe location to breed and give birth. You will kind of "just know" when you see an adult female, it's pretty obvious compared to the males you are posting. In your video, pictures, or in person, you can generally see where the vent is, and then see the tail length from there, and there's a noticeable difference in adult females versus males. It can be difficult with younger snakes as the difference is less noticeable with less snake to see.

Re: How to visually SEX a rattlesnake...

Posted: January 26th, 2015, 9:36 pm
by John Delgado
I was just saying to my wife, maybe a day ago, that I think we have yet to see a female.

We thought for sure 'Betty' was a female -- And looks like now, based on qualified posts, that Betty is a Bert :lol: And I agree ... we have yet to see a female rattlesnake from our rattlesnake world.

And Travis -- Oh ya ... he's a big dawg.

Here's another big'ole dawg - We named him 'Sylvester' and he is only the 2'nd rattlesnake we caught as my first year in field herping. Clearly we did NOT know what we had ... Sylvester turned out to be the BIGGEST rattler we found in 2014. His girth, around the middle, was a whopping 11 inches (measured). He's me and Denise's baby, that's our BIG BOY. We need to, just have to see him again in 2015.

We found him under some big rocks next to a rest stop/picnic/BBQ grill area for 4WD travelers (no camping) -- So ... Sylvester has a very lucky life dining on rodents that dine on the trash of wayward 4WD weekend travelers - He's a KING of the rest stop.



This is not the best pic I have of Sylvester, but it is the only pic that best shows his tail.

ImageSylvester by [email protected], on Flickr

Re: How to SEX a rattlesnake...

Posted: January 27th, 2015, 6:55 am
by gbin
VanAR wrote:Complete aside the sexing discussion:
Bryan Hamilton wrote:
Stohlgren wrote: Females aren't smaller solely due to the cost of reproduction, or female snakes of all species would reach smaller sizes than males. There are also pressures that cause males to be larger, such as the need to complete for mates. Or in your example, larger prey size. In the example of natracines, larger females can have more young and despite the cost of reproduction, females reach larger sizes than the males do.
I'm not trying to generalize to all snakes but for rattlesnakes, it's pretty well established that reproductive costs limit the size of females. My guess is that female natricines devote a smaller proportion of energy to reproduction than rattlesnakes.

Given the similarities in female reproduction between vipers and naticines, its interesting how different their life histories are.
The problem with the hypothesis that combat drives large male SSD is that it only explains why there is selection on males to grow large. It doesn't explain why females don't grow as large as females, nor does it explain why males grow larger than females- the ability of a male to outcompete another male for a female doesn't affect female body size at all. The energetic limitation hypothesis is an attempt to explain why males might grow larger than females in conditions where energy is limiting and male reproductive effort is (presumably) less than that of females, where reproductive effort is defined as the proportion of the energy budget allocated to reproduction. Also- it's interesting that some Vipera and some pythons have combat and small-male SSD.

The hypothesis that large-female SSD is driven by selection on females to maximize reproductive output and an absence of selection on males for combat ability has similar problems explaining all circumstances. There are probably many different selective pressures and environmental constraints that might lead to SSD, and the tough part is distinguishing plastic responses from evolved differences.
To attempt to clarify even further for anyone who might be confused ;) , these organisms can of course be under multiple selective pressures simultaneously, not just one or another. Energetic constraints are at work on both females and males, whatever the species, but they naturally exert greater influence on females given this sex's greater energetic investment in reproduction. Males of some species (such as rattlesnakes) engage in considerable competition for reproductive opportunities, though, so they are under additional selective pressure to become larger even than might otherwise be optimal from an energetic standpoint. This is not by any means a new discovery; Emlen and Oring (1977) famously wrote about the selective pressures on males that result from various mating systems almost 40 years ago. Nor is it at all unique to snakes (or other herps); across taxa, the greatest degree of sexual dimorphism is found in species in which males must compete the most for access to females.

In other words, this looks to be yet another internet forum discussion in which everyone is pretty much saying the same thing, just with different emphasis. :beer:
John Delgado wrote:... only the 2'nd rattlesnake we caught as my first year in field herping... His girth, around the middle, was a whopping 11 inches (measured)...
I must say, this sounds like the kind of thing that all too often ends up badly. Did I miss something above that explains why these rattlesnakes require handling?

Gerry

Re: How to SEX a rattlesnake...

Posted: January 27th, 2015, 9:04 am
by John Delgado
gbin wrote:
VanAR wrote:
John Delgado wrote:... only the 2'nd rattlesnake we caught as my first year in field herping... His girth, around the middle, was a whopping 11 inches (measured)...
I must say, this sounds like the kind of thing that all too often ends up badly. Did I miss something above that explains why these rattlesnakes require handling?

Gerry
No Sir ... very sorry, these beautiful rattlesnakes in my videos did not require handling.

I have found a great respect and adoration for my new friends. As I said in previous comments above, I am a greenhorn. At the time of these video's I did not know about in-situ type photographs and video observation.

When it comes to rattlesnakes, I can teach nothing. I am here at FHF to learn from you nice folks. My wife and I are very lucky and fortunate to have found an untapped cornucopia of rattlesnakes in a about a 1x2 mile section of a 250 square mile mountain range. In 2014 my wife and I, a pair of greenhorn-newbs going out about once or twice a week, found 13 rattlesnakes in a about a 8 week period.

This forum is valuable information and I have learned here that "handling" is not necessary ... ill-advised.

I am very open to constructive criticism, and I only ask that if you see me doing something wrong in my videos it's okay to point that out ... I'm a grown man, I can take it. However, I also ask that with criticism - please provide positive direction so that I may be a better friend to my rattlesnakes.

Please forgive me -- And I have asked my rattlesnake friends to forgive me ... 2015 will be much different.

Re: How to visually SEX a rattlesnake...

Posted: January 27th, 2015, 11:23 am
by gbin
John Delgado wrote:... I have learned here that "handling" is not necessary ... ill-advised.
Thanks for the clarification, amigo, and I'm glad to hear that you're herping safer these days! :beer:

Gerry