cohort vs individual covariate interactions-no way?

[throndh]

I want to check the support for a model where individual size at tagging is hypothesized to affect survival probability (over the period following tagging). However, I have reasons to believe that the strength of size-dependent survival is dependent on density (due to cannibalism) or prey density. That is, I want to construct a model including interaction between cohort covariates and individual covariates. I remember reading Franklin’s contribution to the Second International Wildlife Management Congress in Gödölló, Hungary, a while ago (available from Mark web site: http://www.cnr.colostate.edu/~gwhite/ma ... colRel.PDF). I quote: Another limitation in MARK is that interactions between continuous cohort-level (i.e., year- or age-specific) covariates—such as weather, effort, etc.—cannot be constructed with individual covariates. :shock:
So - I wonder - is this still the case? If so - any suggestions on how I should proceed would be highly appreciated.