I carry a Dachshund named Mojo. He learned from my old weenie dog Tex. Our moto - :If it is down, it is found!". Truthfully they do a wonderful job of blood trailing.
I also use a HD, commercial grade, high lumen, long running ,spot light like the one's utility lineman and firemen use. This quality of spot will penetrate super and lasts for many hours on one charge. I will also use toilet paper to mark blood spots as I go.