Hm. Sorry to be discouraging, but you're not going to get an MS at Berkeley. 🙁 At least, all the science departments I know of (Molecular/Cell Bio, Integrative Bio, Biostat, Bioeng, Biophysics, Chem, Nutrition, even Psych, which is where you'd find the closest thing to "animal behavior") only have PhD programs. Basically an MS is a useless degree in big-time academic research, which is all Berkeley exists for. So, all the science PhD programs here are designed to start straight out of undergrad.
The exception is the Public Health department. The MPH is a professional degree in itself and Public Health also does MA/MS degrees. The link between public health and veterinary medicine is obviously very strong, and MPH/DVM would be a great combination if you have any interests in that direction.
If you really want a masters' in something more behavior or animal-related, you could try looking into the smaller universities around - SFSU, the Cal State schools (rather than the UC schools), that kind of thing. Those may be more geared toward people who want to get an MS to get a raise at their current job, and less toward big-time academic research.
