These dogs do not display any noticeable signs of being in heat. They produce reproductive hormones but don't develop the more usual external signs such as a swollen vulva.  The only way you can really confirm if a silent heater is in heat is by observing the interactions between male dogs and the female dog in question. Male dogs will detect even low levels of female reproductive hormones, which will arouse their intense interest and attention. Be aware that some dogs do "skip" a heat. If they are unwell or their health is below par, or if they have lost weight recently, their body may save its energy and she won't come into heat when expected. This is nature's way of saying her body needs all its reserves to look after number one, rather than being in a state of flourishing good health where she could care for puppies. If you have a couple of male dogs, as well as your female dog who you think may be in heat, pay attention to how aggressive your male dogs are to one another. When more than one male dog is around a female in heat, they will begin to act very aggressively towards one another to prove who is dominant and should mate with the female dog. If you own one male dog and a female dog that you think may be in heat, pay attention to how the male dog reacts to being kept apart from the female dog. If he seems more agitated than normal and whines frequently, he is most likely verbalizing his irritation and not being allowed near the female dog. This is a good indicator that your dog is in heat. Although this is not foolproof and you need to interpret this in the context of the dog's physical changes and the male dog's usual behavior when kept apart from his female pal. Some dogs experience anxiety when separated from a close playmate and this is difficult to differentiate from sexual frustration. If you let your dogs run around together all the time, then observe what happens when your male dog gets near your female dog. If your dog allows her vagina to be licked and sniffed for an extended period of...

How would you rephrase that briefly using Chinese?
有的母狗发情的时候是看不出来的。 注意公狗的攻击性行为。 注意狗狗嘴里发出的声音，并看看狗狗有没有很激动。 观察公狗和母狗之间的互动。