Evolutionary fitness

Felis catus is a remarkably successful species, evolutionarily speaking. Unlike the snow leopard or Iberian lynx, no one is talking about the endangered housecat. Their skill as predators, prolific reproductive capacity and willingness to exist alongside humans (whether in homes or nearby feral colonies) have helped them thrive when other members of the Felidae family have struggled. While these genetic traits mean good things for species survival, they can also mean that often there are just too many cats, especially in mild climates where rodents and other food sources are abundant. Widespread spaying and neutering seem like obvious parts of the overpopulation solution.

Behavior issues

Intact females go into estrus multiple times during their breeding season, crying to get out and making desperate attempts to escape. Besides annoying the owner, the cat seems miserable. And most experts agree — that cat will get pregnant eventually.

Intact male cats spray stinky urine. They also wander if let outside and are much more likely to get hit by a car or attacked by another animal or even human. And their fights result in the caterwauling that can wake neighborhood residents out of a dead sleep.

THE BOND may suffer.

Welfare issues and overpopulation

Animal lovers experience horror at the prospect of mass euthanasias of healthy cats. This horror has been — and unfortunately still is — too much of a reality.

Feral cats live brutish and short lives; they are susceptible to disease, starvation and predation. Trap-neuter-return (TNR) programs — in which cats are captured, sterilized and often vaccinated, then returned to their point of origin — are an attempt to minimize suffering in these wild feline colonies. The idea is that if enough individuals are sterilized, the populations will naturally dwindle over time. Many TNR programs involve surgical removal of the tip of an altered cat's ear to signal that it should not be captured again.

Feline Fix by Five

This campaign, launched in 2016 by a number of organizations focused on feline welfare, seeks to raise awareness of the benefits of spaying or neutering cats before 5 months of age. These benefits include:

1. Decreased risk for mammary carcinoma (the third most common cancer in cats)
2. Elimination of reproductive emergencies such as pyometra and dystocia
3. Avoidance of unintended pregnancies that may occur as early as 4 months of age
4. Potential decrease in behavioral problems linked with cat relinquishment

Effects on adoptability

Sterilized cats are more likely to be adopted from a shelter, increasing their chances of avoiding euthanasia. Recent analyses indicate that about 200,000 cats were euthanized in shelters in 2020.

Health concerns

The risk of a female cat developing mammary cancer is 91% lower higher if she is spayed before her first heat cycle occurs.

There's been a long-standing view that male cats are more likely to experience urethral obstruction if they're neutered before sexual maturity, but this has not been proved in the research.

Spayed or neutered cats are more likely to become obese, potentially leading to metabolic health-related problems. Plus there is some (much-disputed) evidence that cats experience orthopedic problems with early spay-neuter.

On balance, most veterinarians, feline behavior experts, welfare advocates and cat owners agree: The benefits of spaying or neutering before sexual maturity outweigh the risks.