Black tarry stool shows bleeding in the gastrointestinal tract. (dog-health-guide.org)
Rat poison may also cause blood clotting disorders and bleeding, which may manifest as dark tarry stools. (pethelpful.com)
Contact the veterinarian if your pet has bloody, black or tarry stools as these symptoms could indicate damage to the stomach or intestines, which could be dangerous. (1800petmeds.com)