A new Clark County ordinance requiring most pet owners to get their animals spayed and neutered seems to be making a difference. County officials say the number of dogs and cats sterilized last year nearly doubled over 2009. But they say more needs to be done to address the valley’s pet overpopulation problem, and reduce the number of dogs and cats that have to be put to sleep. February has been designated National Spay and Neuter Month, and the Heaven Can Wait Animal Society is offering free pet sterilizations for low-income residents. For more information on the program, call 227-5555.