Idaho Code § 25-2109

If any stallion of less than $250 market cash and assessed value, ridgeling, or any unaltered male mule or jackass over the age of eighteen (18) months be found running at large, the owner must be fined for the first offense twenty dollars ($20.00), and for each subsequent offense not more than $100, nor less than forty dollars ($40.00), to be recovered before a justice of the peace [magistrate] in the name of any person who will prosecute the same, one-half (½) to his own use and the other half to the use of the county school fund.