The Society for the Prevention of Cruelty to Animals (SPCA) says a caravan offering free de-sexing of pets has carried out more than 11,000 operations around the country.
The SPCA says the caravan is having a marked impact on the number of unwanted animals.
Chief executive Robyn Kippenberger says de-sexing costs between $90 and $300 so is not within the reach of every pet owner.
But she says the caravan has had a significant effect in places like Christchurch, Tauranga and Marlborough where it has set up shop.
Ms Kippenberger says it costs $60 million a year to fund shelters, and the fewer unwanted animals there are, the more care and resources can be spent on other services.
Next year the SPCA will be launching a free vaccination programme to community card users from the same caravan.
But it says all SPCA shelters will eventually offer the operation free of charge.
