I have a chihuahua terrier approx 40 pounds and two years old. Yes he is considered overweight for his age/size/breed. I took him out for the first time at a doggy park and it was kind of hot and he started salivating and foaming excessively at the mouth. He has just gotten his rabies shot last year and it's supposed to last 3 years and he has not eaten anything out of the norm for the past few days. when i looked it up it was a possibility that it was from playing too much and getting over excited and heated up. After we took him in the car and home, it was gone--no sign of aggression or anything wrong. If it is from over heating, is there any way i can prevent it next time? May it have been from lack of water during play? (only about 2 hours) He rejected the water we gave him because it wasnt in a bowl.