The use of Cuban bloodhounds in the earlier circa-1840 Seminole War was a big controversy.
I've been trying to understand more what typical slave-catching hounds were like. One complication is that Cuban bloodhounds weren't anything like what we think of as bloodhounds. They had upright ears, and were larger and more aggressive, probably looking something like this:
Here's a crude drawing of one, "Spot," a bloodhound kept at Andersonville prison:
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Those dogs were good at catching people, not so much at tracking a trail by scent, so slave-catchers also kept tracking hounds, which seem to be more like typical hunting hounds today. The testimony from General Wirz's trial goes into a fair amount of detail about the dogs and how they were used, and I suspect it was similar to how slave-catchers used their dogs. For example:
http://books.google.com/books?id=SfELAAAAIAAJ&pg=PA257
But it's hard to tell from any given report what kinds of dogs were being referred to. For example, the "hounds" in the Dadeville ad, I suspect, would be hunting hounds, or a mixture.
Frederick Law Olmsted said, "No particular breed of dogs is needed for hunting negroes: blood-hounds, fox-hounds, bull-dogs, and curs were used, and one white man told me how they were trained for it, as if it were a common or notorious practice. they are shut up when puppies, and never allowed to see a negro except while training to catch him. A negro is made to run from them, and they are encouraged to follow him until he gets into a tree, when meat is given them. Afterwards they learn to follow any particular negro by scent, and then a shoe or a piece of clothing is taken off a negro, and they learn to find by scent who it belongs to, and to tree him, etc. I don't think they are employed in the ordinary driving in the swamp, but only to overtake some particular slave, as soon as possible after it is discovered that he has fled from a plantation."
He has a footnote: "I have since seen a pack of negro-dogs, chained in couples, and probably going to the field. They were all of a breed, and in appearance between a Scotch stag-hound and a fox-hound."
So maybe something like this:
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There are numerous drawings and paintings of slaves being caught by dogs, but the vast majority are by anti-slavery people, who may have been using their imagination and research almost as much as us, rather than being eye-witnesses.
Here's an example of the foxhound type:
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And another of the Cuban bloodhound type, painted in England, c. 1860:
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And one, too big to post, that shows more of the staghound type than either foxhound or Cuban bloodhound:
http://www.sonofthesouth.net/leefoundation/civil-war/1863/november/bloodhounds.jpg
I'd be interested in any images or descriptions of slave-catching dogs by sympathetic southern eyewitnesses, if anyone knows of any, to eliminate the bias of being filtered through northern eyes.