Most form pairs during the breeding season, but in some species, such as fur seals, the gray seal (Halichoerus grypus), and elephant seals, males (bulls) take possession of harems of cows and drive rival bulls away from their territory.
Look for the crooked tail. This is probably the best ways to tell if a cow has been bred: A cow or heifer will have a crooked tail or a tail that is held out in an odd angle than usual for 24 to 48 hours after being serviced by the bull. 1  4 Edit step.
Some does start filling out within the first few weeks of pregnancy while others keep you guessing for months. When a doe's shape seems to suddenly inflate a couple of weeks after breeding, she may be bred. Measuring or weighing at specific times after breeding can be a big help in diagnosing pregnancy.