A dog in heat may appear nervous, easily distracted and more alert than usual. Heat, or estrus, is a period in a dog's reproductive cycle that occurs when a female dog becomes receptive to mating with male dogs, according to WedMD.
The heat cycle is a 21 day cycle that usually starts when a female dog is between six and 24 months old. It is marked by an increase in estrogen levels and the release of mature eggs into the ovaries. A dog displays a variety of symptoms at each stage of the heat cycle. Among other symptoms, dog owners should notice when a dog's personality and appetite changes as these could also indicate that the dog is in heat.
An increase in urination is another noticeable symptom that can be used to determine whether a dog is in heat. She may also initiate sexual behavior with other dogs by elevating her hind towards males and deflecting her tail and tensing her rear legs.
Spaying a dog in heat will give dog owners the ability to decide the appropriate time for a dog to give birth while avoiding the possibility of unwanted puppies. Another benefit of getting a dog in heat spayed is that doing so reduces the chances of breast cancer and reproductive diseases.