Fitting multivariate mixed models with continuous and ordinal dependent variables

Question

I would like to run a multivariate mixed regression MCMC model with two response (independent) variables, namely Boldness scores (continuous variable) and Aggression ranks (ordinal ranks). Trial numbers (integers) are the fixed effect while individual ID is the random effect. I'm using a mixed model approach to partition between-individual co-variance from within-individual co-variance. I would much appreciate if someone lets me know how to do this, and which package to use, preferably in R and what priors to specify. Thank you very much in advance!