The alternative to sterilization is to raise the hunting limits again. We can either brutally wipe out herds of kangaroos, or we can prevent litters. Sterilization is definitely the lesser of two evils. It will be costly and time-consuming, but will effectively curb the over population that Australia is experiencing.
With the overabundance of kangaroos in Australia, all possibilities need to be considered. The culling of kangaroos seems cruel to many. Relocating the kangaroos has also been suggested. Why not consider sterilization? It would not solve the problem overnight but that is not going to happen anyway. It would help the overpopulation problem greatly over the next few years.