Reptile & Amphibian Forums

is it true that everyone who has been successful with couperi (the few, the mighty, the feared) this season are way heavy on females in their hatchlings!!??
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Carl W Gossett
Garage Door Herps
Monument,Colorado...northern territory of the Great Republic of Texas

& its such a dadgummed pity... none of the @#$$!--sobs are here in el....so i mite possess one & stand this infernal place for 1 moe summer....

It's not your imagination. My experience has been heavy females with most of my clutches. Considering the sex of the snake is determined genetically (not temperature related), there might be some really interesting stuff going on here. Perhaps the sperm with the male chromosome are just less likely to make it to an egg than the female chromosome carriers.

Doug T

I wonder if it's been like that in the wild?? More females means more hatchlings....maybe they're trying to make a comeback! Does anyone here know anyone who's studied them in the wild and has any info on this??
Just a thought
Travis.

My experience this season has been exactly the opposite.For the most part nothing but all male production. Pathetic. And of course they refuse food. Joy-joy feelings all around..
Congrats to those with good numbers and an even sex ratio in their clutches.You simply MUST tell us how you did it. I for one will write down every word you type, given my own pathetic results.

Take care,

Fred Albury

YUP, I have seen the same trend in my couperi for the past four years...in an average clutch, I have 1-3 males versus 5-8 females. From the point of view of population dynamics and densities (particularly for couperi and other endangered species), this makes a lot of sense. I would be very curious to see what "wild" populations are doing to see if there are any correlations.

Rob Carmichael, Director/Curator
The Wildlife Discovery Center
City of Lake Forest Parks & Recreation (IL)

Rob, yours is the 2nd post to allude to there being a possible nexus to a recovery strategy via differential sex ratios.
I dont think nature (& im very comfortable that the literature is void regarding this) behaves quite so.
While clutch (fecundity) size can & does vary w/ environmental conditions; favorable resources tend towards larger outputs...the critters themselves do not have a mechanism to select the sex of their offspring...Mendelian genetics fix this at 50:50
For some poikliotherms spps. (tho no snakes that I am aware of) developmental T can influence sex ratios at birth. There could too, tho this is a stretch, be differential rates of mortality on the neonates.
I note in my rockboas, some years I seem to have substantially more sows, other years more boars, over the sum of years; 50:50.

John Gunn

Supervisor (& Wildlife biologist... extrordinaire)
Spur Cross Ranch Conservation Area
Maricopa County, Arizona, USA

I understand that logically Mendelian theory would place the ratio at 50:50. However, that doesn't explain the actual ratios supposedly found in wild populations of various species.

In captive populations, especially after several generations of captive born animals, the ratios may well work out to 50:50 on average, because many of the environmental factors/triggers present in wild populations are non-existent in captive populations.

With most animal species however, collection data and conventional wisdom place the ratios as biased toward a substantially higher number of females in wild populations. Supposedly this is due to the fact that a given chunk of real estate will only support x number of a particular species, and since one male can service several females, then fewer males are needed to sustain the population and the more separate clutches laid, the higher probability of acceptable survival rates of the offspring. I've noticed in field collecting (various species) that at certain times of the year, the ratio of males found is higher, and at other times it may be biased the other way, or about even. I attribute this to breeding activity (males more active), time of day (feeding activity for both sexes), collection methods (areas searched may be frequented more by one sex or another for one reason or another such as suitable nesting habitat), and pure chance.

One would think that (if sex ratio differential triggers exist) factors such as higher food availability would trigger a higher incidence of females to produce more clutches, therefore more animals. Lowered availability of food would trigger smaller clutches or reduced mating activity. I can't think of a logical natural trigger for higher ratios of males.

I don't think that a trigger to overall increase populations in general would exist because nature never intended for populations like Eastern Indigo Snakes to be reduced by human influence.

thoughts?

OK OldHerper, heres my thoughts...in CAPS so you can find em. Before I begin tho...mojo chowed down a fairly large (1 m ) f/t diamonback [DoR] today in an incredibly short time: < 5 min. flat, & now he can barely coil again....

Posted by: oldherper at Sun Jul 6 12:33:39 2003 [ Report Abuse ] [ Email Message ]

I understand that logically Mendelian theory would place the ratio at 50:50. However, that doesn't explain the actual ratios supposedly found in wild populations of various species. AGREED, AS I TRIED TO SAY EARLIER; FOR MANY SPPS THERE IS SEX LINKED MORTALITY FACTORS WHICH SKEW SX RATIOS. THESE DONT LIKELY BEGIN THO UNTIL POST SEXUAL MATURITY; IE THE ASSUMPTION IS THAT NEONATES BEHAVE THE SAME. IN CAPTIVITY THO, W/ EVERY NEONATE NURTURED...50:50 OTTA RESULT GIVEN A LARGE ENOUGH SAMPLE; WHAT WERE SEEING HERE IS THE EFFECT (HIGH VARIANCE)OF SMALL SAMPLE SIZE.

In captive populations, especially after several generations of captive born animals, the ratios may well work out to 50:50 on average, because many of the environmental factors/triggers present in wild populations are non-existent in captive populations. TRUE.

With most animal species however, collection data and conventional wisdom place the ratios as biased toward a substantially higher number of females in wild populations.

THIS IS ESPECIALLY EVIDENT HERE IN DEER WHERE WE SHOOT BUCKS ONLY...WE HAVE BUCKOE RATIOS OUT IN SOME CASES AT 10:100
IM NOT SURE THIS IS A GOOD GENERALITY THO; MANY POPS SEEM TO HAVE EXCESS MALES; LIONS PRIDES/??

Supposedly this is due to the fact that a given chunk of real estate will only support x number of a particular species, and since one male can service several females, then fewer males are needed to sustain the population

ASSUMING POLYGAMOUS SPPS (MOST HERPS/MAMMALS/FISH), FEW BIRDS.

and the more separate clutches laid, the higher probability of acceptable survival rates of the offspring. GENERALLY TRUE

I've noticed in field collecting (various species) that at certain times of the year, the ratio of males found is higher, and at other times it may be biased the other way, or about even. I attribute this to breeding activity (males more active), time of day (feeding activity for both sexes), collection methods (areas searched may be frequented more by one sex or another for one reason or another such as suitable nesting habitat), and pure chance. I TOO HAVE SEEN MUCH OF YOUR THOUGHTFUL OBSERVATIONS ABOVE.

One would think that (if sex ratio differential triggers exist) factors such as higher food availability would trigger a higher incidence of females to produce more clutches, therefore more animals. Lowered availability of food would trigger smaller clutches or reduced mating activity. I can't think of a logical natural trigger for higher ratios of males. IDEALLY FOR MAX POP GROWTH DURING TIMES OF PLENTY; PARTHNOGENESIS; ALL FEMALE POPS HAVING MULTIPLE CLUTCHES (THAT ARE ALL FEMALE CLONES OF THE MOTHER)GETS YOUR POP RECOVERY THE FASTEST. ALAS THO, FOR SEXUAL REPROD. SPPS. MY LAST UNIVERSITY LEVEL UNDERSTANDING OF SEX RATIOS WAS 50:50 POST MIOSIS (INITIAL CELL DIVISION). MORE MALES MIGHT BE USEFUL IN SOCIAL SPPS. [BABOONS/HUMANS/?]EXHIBITING GROUP DEFENSE WHERE MALES DO THAT DEFENSE & PREDATORS
ARE ON AN UP-CYCLE.

I don't think that a trigger to overall increase populations in general would exist because nature never intended for populations like Eastern Indigo Snakes to be reduced by human influence. THATS MY CONCLUSION TOO, THEY ALREADY INCREASE @ A PRETTY GOOD RATE: 8-12/ANNUM/ADULT FEMALE.

thoughts? GOOD CYBER-CHAT.....rr

.

I forgot if sex is or isnt....zzzz
Hey.... wait no...I am just kidding spousal-dominatrix...aaarrggghhhhh.