Section 162. The aldermen or selectmen may offer a reward of not more than twenty-five dollars for the killing of any dog found worrying, maiming or killing live stock or fowls, thereby causing damages for which their owner may become entitled to compensation under section one hundred and sixty-one, or for evidence which shall determine to the satisfaction of such aldermen or such selectmen who is the owner or keeper of a dog which has been found to have so worried, maimed or killed any live stock or fowls. The county commissioners, except in Suffolk county, shall pay any such reward from the dog fund, upon a certificate signed by the aldermen or selectmen.