venomstreet said:
Like I said, from what I've seen, higher temps do tend to throw more males. Not in every case obviously, but it seems to in general.
I would just like to point out that unless you've kept good records, and have sufficient data to show that your trend is statistically highly improbable as a result of random sampling, it isn't. Humans are notoriously poor at recognizing trends in data, and are also known to "see" or "notice" trends they suspect are there. This is why we have to do double-blind drug testing experiments. People often see what they want to see or what they think they see. People also have no "feel" for what is expected from random sampling. We might think that if we flip a coin 10 times and 7 times we get heads, that the coin is weighted improperly when in fact, 7 out of 10 heads is not all that uncommon a result. This is why we have many, many people gainfully employed as statisticians.
From what I have read (which is admittedly very little), the people who actually DO deliberate experiments using sample sizes sufficient to make a reliable conclusion one way or the other (note that an entire clutch is one ONE datum here) have not been able to demonstrate TSD in snakes.
I could be wrong about that and there could be new data out there, but hobbyist data, generally, will not have sample sizes sufficient to address this particular question.
Here is an abstract from a recent article that refers to TSD in snakes and that it seems not to occur. If you want the entire article so that you can track down the citations referring to TSD in snakes particularly, PM me and I'll send you the pdf. There's a Quarterly Review of Biology paper in the bibliography about Sex determination in reptiles. I doubt these authors would have concluded their abstract as they did if it were not generally accepted in the field of biology that TSD does not seem to be important for snakes.
Title: Phenotypic consequences of nest-site selection in black rat snakes (Elaphe obsoleta)
Author(s): Blouin-Demers G, Weatherhead PJ, Row JR
Source: CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE 82 (3): 449-456 MAR 2004
Document Type: Article
Language: English
Cited References: 38 Times Cited: 1
Abstract: Nest-site selection is the only behaviour that can be considered parental care in most oviparous reptiles because eggs are abandoned after laying and because incubation conditions resulting from nest-site selection can have profound effects on offspring. During a 7-year study of black rat snakes, Elaphe obsoleta (Say in James, 1823), we investigated phenotypic effects of incubation temperature on hatchlings, monitored temperatures in nests, and determined the preferred nesting temperature. Temperatures of communal nests were higher than those of single-female nests. In the laboratory, females preferred to nest at temperatures most similar to those of communal nests. Hatchlings from eggs incubated at temperatures similar to those in the warmer communal nests hatched faster, were longer, swam faster, were less aggressive, and had fewer scale anomalies than hatchlings from eggs incubated at temperatures similar to those in single nests. A possible disadvantage of communal nests is that eggs in communal nests may be at greater risk to parasitism by Nicrophorus pustulatus (Herschel, 1807).
The incubation experiment allowed a test of a key assumption of a model proposed to explain environmental sex determination. Contrary to that assumption, we found no evidence that incubation temperature affected males and females differently. Our results might explain why temperature-dependent sex determination appears not to occur in snakes.
