When it comes to euthanasia statistics from shelters and pounds around Australia, cats and kittens lead by a country mile.

The supply far outstrips demand.

Globally, unowned domestic cat populations have boomed, driven in part by what scientists describe as "their phenomenal reproductive success".

A single female cat can produce between one and three litters of kittens per year, consisting of (on average) one to six kittens - though I've seen litters of ten kittens.

That's a lot of mouths to feed.

Don't get me wrong, I love cats. I spend much of my working day treating them, and then I come home to an affectionate cat.

A well cared-for, well-managed cat is a wonderful companion.

But I have seen the dark side of overpopulation.

Unwanted litters are common, and often end up being cared for in shelters or by rescue groups who do their best to find forever homes for these youngsters.

Those who don't end up in shelters join stray cat populations, often experiencing poor welfare and impacting local wildlife populations already under stress from habitat destruction, motor vehicle trauma, global warming and other predators including foxes.

The euthanasia of healthy, unwanted kittens - because there isn't enough room, resources or space to care for them all - is devastating, but the reality is that it still happens.

When it comes to overpopulation, prevention is much less traumatic than cure.

A recent study published by my colleagues Loic Mazeau, Claire Wylie, Lara Boland and Julia Beatty in Nature (https://www.nature.com/articles/s41598-020-79513-6) found that Australians are pretty good at desexing cats.

Over 83 per cent of cats visiting the vet are desexed - one of the highest rates in the world.

But they argued we're not getting the timing right.

To tackle overpopulation, we need to close what they call "the pregnancy gap" by desexing cats before they hit puberty.

Most cats hit puberty somewhere in the region of five to nine months of age, but some blossom early, at just over three months of age.

Traditionally, veterinarians recommended desexing cats at around six months of age.

The problem is, many cats have outdoor access (whether intended by their owners or not) before the age of six months, offering plenty of opportunity to find a mate.

We now know that some cats are capable of getting pregnant by four months of age. Thus desexing at six months still yields a potentially very large number of unwanted litters.

Early-age or pre-pubertal desexing, performed when kittens hit one kilo in bodyweight, has been standard in many shelters for decades.

That isn't surprising - shelter managers know better than anyone the impact of early-age pregnancy on the feline population.

Local governments have come on board, with an increasing trend of charging higher registration fees to owners of cats not desexed by the age of four months.

In the ACT, kittens must be desexed by three months of age.

Pre-pubertal desexing is safe.

Surgically, it involves the removal of less tissue.

It is quicker, meaning a shorter anaesthetic.

And, in my experience, desexed kittens are awake and eating as early as 30 minutes after surgery.

Owners of desexed cats don't have to experience territorial urine spraying, or the persistent and often distressing calling of a cat that goes into season.

While kittens are adorable, we need less of them in order to ensure that those kittens who do exist can find a suitable home and live their best life.

Dr Anne Quain BVSc (Hons), MANZCVS (Animal Welfare), Dip ECAWBM (AWSEL) is a lecturer at the Sydney School of Veterinary Science and a practising veterinarian.