After sterilization, the male cat will no longer secrete eggs and male hormones, which will make the female cat think that it is a cat of the same sex, which will make the female cat want to occupy the territory. If two cats live together since childhood, the male cat will be affected by the surgery. The change in body odor will cause the female cat not to recognize it, and the female cat will not be able to accept the appearance of a new partner, so she will be aggressive towards the neutered male cat.