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RE: Anyone read this about Baja herps?

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Posted by: Aaron at Fri Jul 16 00:16:45 2010  [ Report Abuse ] [ Email Message ] [ Show All Posts by Aaron ]  
   

The '85% of females gone', were gone from the study site only, not the entire species and possibly not even from the entire locality from which the study site may have been just a small part.

If you follow the link and read the whole thing you can see a number of references to counts of individual specimens that were part of the study. Such as:

"Snakes often spend long periods of inactivity in a retreat site, such as under rocks or in crevices (Webb & Shine 1998b). The mean number of rocks used by individual snakes in a single year was 2.03 (n = 33) (Webb & Shine 1998b)."

The part were it says (n=33) means 33 specimens. This was the greatest number of individuals I could find reference to, regarding the Webb and Shine study from which the 85% of females were lost. I admit they do not come right out and say there was only 33 specimens involved in the study, that is only the greatest number I could find reference to. Other refences point to lower numbers:

"Snakes moved more in woodland habitat, moving an average of 159 m (n = 20) between retreat sites and moving on 35% (n = 20) of days."

In the above case (n=20) means 20 individuals were observed.

"The mean home range size of snakes in woodland was 3.43 (2.86 SD) ha (n = 18) during a three-year study."

Above (n=18) means 18 specimens.

So as I said the greatest number of specimens that appear to have been observed at any one time appears to be 33. I admit this doesn't mean that's all the specimens they studied but it's probably pretty close because all other references were to lower numbers. Those lower numbers(n=20) and (n=18) were possibly redundant to the (n=33) but this article doesn't say. Given that the article does not metion any greater observation that 33 I will have to go with that for the following examination.

It does not say how many were females but assuming about half(17) of the 33 specimens were female then what we have cited here is one study site from which it appears about 14(85% of 17 = 14) individual females were removed. I did admit that this was disturbing but I do not find the potential removal of approxiamately 14 females from one study site to be the most significant thing in that article.

I also posed the question(paraphased), 'Does the sutdy site represent the entire population, or just a small and perhaps easily accessable portion of a greater population?' The answer cannot be obtained from the article I cited but since snakes are much more mobile than humans and the species in question typically inhabits rugged mountain ridgelines, I highly doubt the authors were able to access the entire population. Likely the study site only included a small portion of that particular population, as is typical for most reptile studies in rugged terrain. If that is the case(and I believe it is) then the 85% of females removed from the study site could be considerably less significant to that locality's population as a whole than it is to the study site alone.


   

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<< Previous Message:  RE: Anyone read this about Baja herps? - dustyrhoads, Thu Jul 15 22:53:13 2010