I have a friend on the east coast and for the last few years his company has had ongoing dealings with a wealthy South American businessman whose family used to control the National Bank of Bolivia. This family has maintained a vast estate in southwestern Bolivia for approximately 200 years. It comprises several hundred thousand acres.
Last year my friend and his employer were invited to the rancho or estate for several days. While there . . some of the resident employees, who are basically native Indians . . went on a hunt for a jaguar who was killing calves and lambs. My friend ended up not being present when the jaguar was caught and killed with the help of some of the ranch's dogs, but he was excited and called me later to tell me about it.
Of course I've been harassing him with questions and requests ever since. All of my info is second hand (at least) and there is also something of a language barrier. The family's primary concerns now are more in finance and petroleum so the businessman himself has never had any direct involvement with the dogs or any real interest in them or cows or hunting, etc.
The ranch is no longer a commercial ranching operation but they still maintain a herd of cattle and still keep the dogs even if only out of a sense of history or nostalgia. At one point the dogs were used in some manner on the cows. It sounds like they might have been more of a hunting/catching dog than a lead dog or one used for penning the cows. But because of the Spanish influence in Bolivia and on the family in particular . . I'm assuming they would be more of a cur type cow dog than a heeler or a collie, etc.
The estate owner told my friend that when he was a boy the old women of the family would sing a song to the children about his grandfather or great grandfather. As the song goes . . sometime around 1920 the man of the family took some of his working cowboys up into the mountains to kill an extremely dangerous "tigre" that was a menace to not only livestock but some of the local villagers as well. He took all of his dogs except a young pup and a couple of old dogs who were past their prime. Several days later he returned unsuccessfully after having one of his "gauchos" and every single one of the dogs killed. The song goes on to say that the following spring the man returned to the mountains, but this time he went alone and took only the one pup who had by now grown into a young dog called el Lucho. You can probably guess that the man and dog killed the jaguar by themselves or else their wouldn't have been a song.
Also . . there was some famous white hunter of jaguars in the 1920s or 30s who supposedly got his most famous dog from this family. The hunter's name was either Samuel something . . or something Samuels, and there is alleged to be a book written about him. I've looked all over the internet and haven't found anything but I'm thinking it might just be a Bolivian book and so would've been written in Spanish.
The dogs have always pretty much run loose on the ranch so nowadays most of the male dogs are neutered for practical purposes. It doesn't seem anyone pays much attention to which dogs mate and there are no records kept of any breedings . . or at least not for the last fifty years or more. There are no nearby neighbors or towns to produce many stray dogs but there are villagers on the estate itself and some of them keep a type of dog known as Andean Tiger Hounds that could have intermingled in the gene pool of these ranch dogs.
Strangely though . . these Andean Tiger hounds are one of only three known dogs that produce separated, double nostrils . . and since the ranch dogs don't possess that trait . . I'm assuming there isn't a lot of interbreeding. But to be fair . . the ranch dogs could be half Shih Tzu for all the evidence I have.
Here is one of a few pictures I've managed to get from my friend. The dogs all look like slight variations upon this one. Some have no saddle. On some the saddle covers much more but has more of a smutty or sable appearance than what we would call black and tan. This is the main dog used to catch last year's nuisance jaguar. I don't know his name in Spanish . . but my friend says he was told it translates to "Baby Eater" . . lol.

Anyway . . I thought somebody might find this story interesting. One more hint at a possible Spanish origin for working/herding dogs in the new world.