John Frame Murray, 57, and his son, also John, 34, dug into what was thought to be a badger sett at Drummond Hill, near Sandilands, Lanark, on February 2, 2012.
They were spotted by people who managed to take photographs of them in the act and animal welfare officers were called in.
The Scottish SPCA, which led the investigation, searched the mens' homes in Earn Gardens, Larkhall, and discovered three dogs, all of whom had injuries which suggested they had been in face-to-face confrontation with badgers.
The men were found guilty at Hamilton Sheriff Court last month of three charges contrary to the Protection of Badgers Act 1992. They were sentenced yesterday and told to carry out community service within nine months.
Scottish SPCA Chief Superintendent Mike Flynn said: "This was a very complex and challenging investigation requiring technical forensic work and a great deal of time and specialist resources.
"During the course of our investigation we found and seized three dogs, two Patterdale terriers and one Staffordshire bull terrier.
"Both Patterdales were found to have severe injuries to their lower jaws, including tearing to the lips and missing teeth. The Staffordshire bull terrier had injuries to its upper and lower lips and nose and missing teeth.
"Following the outcome of this case we are very pleased we can now find these three dogs the loving new homes they deserve.
"This case serves as a warning that we will do all we can to identify and detect persons involved in this barbaric activity."