Omgosh the little guy must be super quick to catch a rabbit
.. I dont know if the blood is making him act that way, I have never had that experience. My little guy will run around the yard barking away and I sometime think its the birds in the trees and he can hear the noise but not see them that gets him all riled up.. Sorry I cant be much help, Hopefully someone comes along that knows a little more about it..
I will say tho I know squirrles can carry Leptosperosis(sp) or Lepto, my Fred just got over a bout of this this last few weeks, normally its contracted thru urine of squirrels and raccoons and such. Im only mentioning it cuz if hes quick enough to catch a rabbit he could get somtehing that may carry that. THe first signs we had we that he seemed so sad and lethargic but after a few weeks (cuz we thought it was trama from fireworks making him act this way) he ended up in kidney failure and was very sic. Hes doing much better now, but just mentioing it so u know its out thier.