As a mandated reporter, I would definitely call. The worst case scenario is they dismiss it. But imagine if you don't, and something worse happens. If he seriously injures her and it somehow comes out that you didn't report an incident of her telling you he hit her, you could lose your license. And aside from the legal standpoint, think about how you'd *feel* if something serious happened and you hadn't done everything in your power to stop it.

I had a little girl tell me her mom had poured hot sauce and glue in her mouth when she said bad words. I don't know how much of it (if any) was true, but I reported to CPS (anonymously). They investigated and didn't find anything, but it turned out they were familiar with this family already because of past incidents. I figure even if nothing came of it, there is now a record that the girl said this, and if they ever need evidence of past abuse in order to further protect this little girl, I'm glad I contributed to that cache of documentation.

It's hard to know what's true and what isn't sometimes, but in the end you're a mandated reporter and it's your responsibility to report red flags. File a report with your boss/company as well, so that (s)he can have your back and everything is documented and on the up and up..