The intact dog

When: Usually first between six and fifteen months, later in large and giant breeds. Most dogs cycle roughly twice a year, though some giants go annually.

How long: About two to four weeks in total, in stages. Bleeding and swelling come first; the fertile window is typically in the second week, when the discharge often lightens.

What you will see: Vulvar swelling, bloody then straw-colored discharge, increased licking, more frequent urination, restlessness, and sometimes a personality change in either direction.

Managing it: No off-lead walks and no dog parks for the whole cycle — intact males detect a female in heat from remarkable distances, and gates and fences fail. Walk at quiet times. Washable belly bands or dog diapers help indoors. Keep her securely separated from any intact male in the house, including relatives, because dogs do not care.

A life-threatening uterine infection in intact females, most often in the weeks AFTER a heat cycle, and more common with each passing year. Signs: drinking and urinating far more than usual, lethargy, loss of appetite, a swollen belly, and sometimes a foul discharge — though a closed pyometra produces no discharge at all and is the more dangerous kind. This is an emergency requiring surgery, and delay kills. If you keep a female intact, know this one.

Common, normal, and unsettling to watch. Roughly four to nine weeks after a heat, an unbred female may produce milk, nest, mother toys, and go off her food. Most resolves in two to three weeks without treatment. Do not milk the mammary glands — it prolongs it. Persistent cases, or a hard hot painful gland, need a vet.

Roaming and escaping are the main practical risks, and testicular tumors and prostate enlargement the main medical ones. A retained testicle — one that never descended — carries a significantly higher cancer risk and is a reason to neuter rather than wait.

Do not try to separate a tie — you can cause serious injury to both. Call your vet promptly; there are options, and they are time-sensitive. An unplanned litter is a large undertaking, and a frank conversation in the first days is better than a decision in week six.

If you are considering breeding: health testing of both parents first, verified on ofa.org, and a frank look at whether this pairing improves anything. Most litters do not, and shelters carry the difference. See Expecting puppies, which leads with the caution for a reason.

· Society for Theriogenology (therio.org) — veterinary reproduction specialists
· Merck Veterinary Manual (merckvetmanual.com) — free online
· Cornell Riney Canine Health Center (vet.cornell.edu)
· American Veterinary Medical Association (avma.org)

Recognizing pyometra is the whole value of this page, and it costs nothing to know.