Is there anyway to check where competition getting hits from?

I have a certain set of keywords where one of my main competitors seem to be getting over 800 unique hits a day. The thing is, they only have 45 or so backlinks, and I can't seem to find out where or how they would get that many hits. I don't think they have advertising anywhere, and judging by their bounce rate, their hits seem legit. Is there anyway at all to check where a website is getting their traffic from? Thanks.