Reptile & Amphibian Forums

One of my pals in the field has posed this question to breeders:

What can you tell us about sex ratio of your clutches?
In my years of breeding, I’ve had some high male and high female years…overall my ratio has been about 60-40 males to females.

In this study, interestingly there is a 2:1 male to female ratio among marked snakes. This would lead one to believe that maybe males are just easier to find (out cruising more often) BUT…among RE-CAPTURES, females are much higher, indicating that females, when they are around, are actually easier to find than males…and perhaps there are just a lot more males out there.

So…what can you share about sex ratio in your captive hatched clutches??

PS: Just another example of how we can help the folks doing wild studies through captive observations…

Re captures in females may mean they stay close to home while the male is out cruzing looking for some action?
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"Life without risk is to merely exist."

The sex ratios are just like people's..XX/XY chromosomes determine the sex..Although there is some evidence in humans that the X chromosome(female) carrying sperm are more vigorous..No reason to think it would be different in any animal..Territory.. Fighting for females and brreding "rights", chasing other males(lesser) out of "their" territory would account for the difference in the wild..Just like Elk, deer, lions etc..
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Carl W Gossett
Garage Door Herps
Monument,Colorado...northern territory of the Great Republic of Texas

i agree with carl that there "should" be a 50:50 male:female ratio, but it still would be interesting to see if the captive animals are actually producing this. it would also be a sort of preliminary test of people's willingness to offer their data for assistance.

however, the actual numbers (not percentages) are needed to test whether captive indigos produce a 50:50 sex ratio. if people are willing to go to their books and share their sex ratios by clutch, someone could run the appropriate statistical test. this could be done offline if anyone was leary of divulging such info.

matt

Robert Bruce would be an exelent source since he made 90 Indigo last year and should have another hundred this year 190 animals should be a good baseline for this information.
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"Life without risk is to merely exist."

Even though I and many others disagree with many of his methods, we can not dispute that he has produced many babies & could provide some valuable info in this discussion.

Eric
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If Jesus is your co-pilot, you'd better change seats!

Dean,

In a way, you are comparing apples to oranges. Just because the ratio of captured snakes is say 5:3, that doesn't reflect the ratio of sexes at hatching. The ratio of a population changes with age. What you would be seeing is the survivorship ratio amoung the sexes.

Researchers are just trying to gather as much data as possible.

The fact that more males have been found, but females are easier to re-catch doesn't necessarily mean there are more males.

But...understanding the sex ratio of hatchlings is certainly part of the big picture.

I think Dean's point here is just to gather basic data from captive animals. This would help both field workers, and perhaps also other breeders. Not sure why all the Dry breeders out there haven't just reported their numbers rather than questioning the request. Whether its primary (conception), secondary (hatching) or surviving sex ratio, it's all important.

As many of you know, most reptiles exhibit one form or another of TSD. But most animals, including mammmals and probably including humans, do NOT exhibit 50-50 sex ratios at conception or birth under all conditions. There is good evidence in many mammal species that females can alter the sex ratio of their litters, producing more females when conditions are good, and more males when conditions are poor (since all females, even sickly underfed ones, get to mate, whereas males are often excluded when competition is tough).

It would be interesting to know if some snakes exhibit this, in addition to manipulating clutch sex ratio by TSD.

Good to see you posting Dean. This is very interesting stuff Dean. In my 15 years of breeding indigos, and, after going back and looking at my data, I have far greater females than males in a given clutch (on average). I crunched my numbers (quickly, so it may be a bit off) and found that in an average clutch of 9 eggs, I will get 3 males and 6 females; go figure. My hunch is that males are more readily seen in the field due to their far ranging capabilities compared to females.

Rob

>>One of my pals in the field has posed this question to breeders:
>>
>>What can you tell us about sex ratio of your clutches?
>>In my years of breeding, I’ve had some high male and high female years…overall my ratio has been about 60-40 males to females.
>>
>>In this study, interestingly there is a 2:1 male to female ratio among marked snakes. This would lead one to believe that maybe males are just easier to find (out cruising more often) BUT…among RE-CAPTURES, females are much higher, indicating that females, when they are around, are actually easier to find than males…and perhaps there are just a lot more males out there.
>>
>>So…what can you share about sex ratio in your captive hatched clutches??
>>
>>
>>PS: Just another example of how we can help the folks doing wild studies through captive observations…
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Rob Carmichael, Curator
The Wildlife Discovery Center at Elawa Farm
Lake Forest, IL

Dean,

Interesting info. My own personal observation,over the last 16 years, is an average of a 70/30 ratio split males to feamles.
I beleive that lot of it may have had to do with temp fluctuations in my snake room, but that is just a guess.

I have had years where it was a 20/80 ration(Males to females).

Best of luck with this infom thanks for all the great work that you do on our behalf.

Sincerely,

Fred Albury