 Hello everyone,

Apologies in advance, as this is partially a stats question and partially an R question.  I have been using a GAM to model the activity level of bats going into and coming out from a forested edge.  I had eight microphones set up in a line transect at each of eight sites, and I am hoping to construct a model for each of 7 species.  

My count data has a reverse J-shaped skew and is overdispersed with a fair amount of zeros, and I haven't found any transformations that will completely normalize it (I've tried square roots and logs).  Meanwhile, the variance in call numbers  varies between sites and between microphones.  I wanted to use a GAMM to incorporate varComb and varIdent, but these can only be applied on data with a gaussian distribution.  

Are there any packages I should be looking into that I don't know about that will apply a variance structure on a negative binomial distribution?  Or is there some transformation that I should be using that will solve my normality issues?  I've been searching the R-help boards, everything in Zuur and Woods, but I haven't found an answer yet.  

Thanks very much, I am very appreciative of any help I can get on this matter.

Sincerely,
Meredith Jantzen
M.Sc. Candidate
Department of Biology
University of Western Ontario



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