The Nova Scotia Duck Tolling Retriever is a medium-sized gundog bred primarily for hunting. It is often referred to as a 'toller'. However, like almost all dog breeds, certain genetic disorders are known to occur in the breed. This is sometimes blamed on a relatively small gene pool. As many as 1 in 6 Tollers may have autoimmune thyroiditis. Symptoms of thyroid problems includes weight gain, skin and hair problems including hair loss, weakness, cold intolerance or infertility.