How old is my pet really, and what's due now?

The first year of a cat's life is worth about fifteen human years and the second about nine more, putting a two-year-old cat at twenty-four. Each year after that adds roughly four. So a seven-year-old cat is about forty-four and a fifteen-year-old around seventy-six. The AAFP treats seven to ten as mature adult and ten upwards as senior.

No, and it is worst precisely where people use it most. A one-year-old dog is sexually mature and skeletally almost finished — closer to a fifteen-year-old human than a seven-year-old. Ageing then slows. The 2020 formula from DNA methylation research, sixteen times the natural log of age plus thirty-one, tracks the real curve far better.

It runs opposite to the usual mammal pattern where bigger species live longer. Within a single species, large dogs grow much faster to a much larger adult size, and that accelerated growth appears to come with faster cellular ageing and higher cancer rates. A Great Dane is geriatric around seven; a Chihuahua of seven is middle-aged.

It depends on adult size. Small breeds at five to six months, before the first heat, when the mammary tumour benefit is largest and there is no orthopaedic cost. Medium at six to nine months. Large at nine to twelve, and giant breeds at twelve to eighteen, because spaying before the growth plates close raises the risk of osteosarcoma, cruciate rupture and urinary incontinence.

By five months. That is the "Fix Felines by Five" consensus supported by the AAHA and AAFP. Cats can come into heat as early as four months, the mammary tumour reduction is around sevenfold when done before six months, and the surgery is quicker and lower-risk in a young cat than in one already cycling.

The protective effect is large and it decays fast. In dogs, spaying before the first heat is associated with a dramatically reduced risk of mammary tumours; after the first heat the protection drops sharply, and after the second most of it is gone. Since roughly half of canine mammary tumours are malignant, this is the main argument for the early end of the window.

The core series — distemper, adenovirus, parvovirus and parainfluenza — starts at six to eight weeks and repeats every two to four weeks until at least sixteen weeks. Rabies is added at the age your state or county requires. Non-core vaccines such as leptospirosis, Bordetella and Lyme depend on where you live and what the dog does.

Antibodies from the mother protect the puppy early but also block the vaccine from working, and they fade at an unpredictable point somewhere between six and sixteen weeks. Repeated doses are not cumulative topping-up: each one is another chance to catch the window after maternal antibodies drop and before the puppy is exposed. That is also why the final dose must be at sixteen weeks or later.

It is treated as unvaccinated. That means starting the core series over: typically two doses three to four weeks apart, plus rabies as your jurisdiction requires. Titre testing can sometimes demonstrate existing immunity, but it does not satisfy rabies law, which is written around documented vaccination.

About two weeks after the final dose of the core series, so realistically around eighteen weeks. Before then the puppy may be unprotected, and parvovirus survives in soil for months and kills. Socialisation still matters enormously in that window — do it with known, vaccinated adult dogs in private spaces rather than public ground.

A well-kept house rabbit lives eight to twelve years, with dwarf breeds at the top of that range and giants at five to seven. Neutering extends it substantially, particularly in females, where uterine adenocarcinoma is common in unspayed does over four. Diet and dental health are the other two big determinants.

Once the human-year equivalent passes roughly fifty, twice a year rather than once, with bloodwork at each visit. For cats that means from about seven years, for large dogs from about six, and for small dogs from about nine. The interval shortens because early kidney, thyroid and cardiac changes are detectable long before they are visible.