I know herps aren't the most saught-after animals but how do they actually estimate the population of a particular subspecies?
The truth is they don't. For most herps in the US, there really aren't very good population data. Something gets protected when there is credible evidence that
a. there are less of them than there used to be in an area and protection might benefit the taxon
or
b. the taxon has such a restricted range that it could suffer from any disruption (collecting, habitat loss).
Collecting may possibly be a problem for a species here or there, but the biggest threat all herps face today is habitat loss. And unfortunately, you don't need a hunting license to drive a bulldozer and no one counts what you kill.
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Chris Harrison
San Antonio, Texas