As of 2013, an estimated 75% of 700 million dogs worldwide were free to roam and reproduce, resulting in overpopulation, high mortality rates and poor health.[2] The main management approach is surgical sterilization, i.e. the removal of testes or ovaries, often performed through trap-neuter-return strategies.[3] However this approach requires significant resources, including appropriate facilities.[4] If successful, non-surgical approaches may be a more humane, economic and time-efficient option,[3] although no effective permanent treatment is yet available.