My honest opinion on the matter is this:
Traffic (number of threads/posts made by folks on a particular subject) is the basis I prefer to use for trying to decide if a request for a new forum is something that would work or not (unless the big boss man overrides and wants a new forum anyway). Traffic therefore tends to be the driving force on what gets a new forum and what does not. Popularity alone is not always going to be enough. We need to be able to justify the needs of the members versus our ability to support new forums with sponsors and/or with sufficient traffic (which attracts the advertisers). As much as I would love to create indivdiual forums for all types of species, it's just not always possible.
To give an idea of how the python forums compare to one another: (this is a generalized monthly average)
Pythons: General Forum
-- 350 threads / 1,250 posts / 12 sponsors
Pythons: Ball
-- 390 threads / 2,100 posts / 12 sponsors
Pythons: Blood
-- 90 threads / 550 posts / 3 sponsors
Pythons: Burmese
-- 90 threads / 400 posts / 6 sponsors
Pythons: Carpet/Diamond
-- 65 threads / 250 posts / 2 sponsors
Pythons: Green Tree
-- 30 threads / 100 posts / 7 sponsors
Pythons: Reticulated
-- 45 threads / 200 posts / 6 sponsors
The green tree python and reticulated python forums may not be very active compared to the others, but they have the backing of several sponsors to help keep them going. The Carpet/Diamond python forum is actually a bit higher than the numbers suggest since there are folks who like to post discussions about Morelia species. in the General Python Forum but not always in the other forum too.
Womas/BHPs/Aspidites and childrens/spotteds/Antaresia are the two most logical python combos that currently seem to be the most "popular" on the general python forum and would theoretically speaking stand the best chance at a forum of their own. However, looking at them more closely, each of those groupings seem to be running about dead even on generating 6 threads / 24 posts per month (on average). The traffic is not sufficient to really justify splitting either of those groupings out from the general python forum without the benefit of sponsors to help back the forum(s) up.
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PHWyvern