The utility model discloses a kind of necklace of reduction vagrant cat dog fertility comprising a necklace ontology, gender identification mould group and a unhappy property electric energy production mould group. Necklace ontology set is worn over the neck of pet or vagrant cat dog. When at least two pets of the same race or vagrant cat dog are close to each other to a specific range, gender identification mould group recognize the grade animals be the opposite sex when, the unhappy property electric energy production mould group just generates the electric energy such as electric current, electromagnetic wave or electric field, promote anisotropic animals that must be located remotely from each other, it uses and anisotropic animal is avoided arbitrarily to contact and give birth to, the contact of female animals is reduced, and then as far as possible reduces the procreation of vagrant animal, and reduces cost and the manpower of birth control surgery.本新型揭露一種降低流浪貓犬生育的項圈，其包括一項圈本體、一性別識別模組及一不悅性電能產生模組。項圈本體套戴在寵物或流浪猫犬的頸部。當至少二個同種的寵物或流浪猫犬相互接近至一特定距離，性別識別模組辨識該等動物為異性時，該不悅性電能產生模組便產生電流、電磁波或電場等電能，促使異性的動物們必須相互遠離，藉以避免異性動物任意接觸而生育，降低雌雄動物的接觸，進而盡可能的將流浪動物的繁衍降低，及減少節育手術的花費和人力。
