Introduction Kangal shepherd dogs, one of the indigenous shepherd dog breeds of Turkey, are preferred as guard and shepherd dogs around the world due to their majestic appearance, bulky figure, agility, bravery that enables them to stand against wild animals larger than themselves, harmlessness and compassion toward children and weaker animals, and loyalty to their owners (1-5). The Kangal shepherd dog is found in many countries around the world, and there are Kangal shepherd dog breeding clubs in some countries such as USA, Belgium, and France (6). The reasons behind the high preference rate of Kangal shepherd dogs are that they execute the assigned duty perfectly and have the skill to rapidly adapt to the environment. Their ability to adjust their thermoregulation mechanism also plays a significant role in the rapid adaptation of Kangal shepherd dogs to the environment. The tongue plays a role in some functions such as making sounds, sucking, eating, and regulation of the body temperature in dogs. As can be the case in every organ in the body, congenital or acquired abnormalities can be found in the tongue. Some of the abnormalities can be listed as aglossia, microglossia, ankyloglossia, and lingua bifida (7). Ankyloglossia (Figures 1 and 2) is a genetic disease seen in humans and rarely in Kangal shepherd dogs, which is known as incomplete release of frenulum linguae, which ties the tongue to the mouth base, or thickens the tongue due to cell proliferation, and thus preventing the release of the tongue (8-10). Tepeli (11) reported that Kangal shepherd dogs were free in their natural life and acted independently. However, various environmental conditions may cause stress in Kangal shepherd dogs. There is no information in the literature regarding the effect of ankyloglossia on physiological and stress behavioral parameters in Kangal shepherd dogs. Therefore, in this study, the aim was to compare some of the physiological and stress behavioral changes in Kangal shepherd dogs with and without ankyloglossia. 2. Materials and methods 2.1. Animal materials In this study, a total of 24 Kangal shepherd dogs, 11 of which have had ankyloglossia and 13 of which did not