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Reproductive Cycle of Cats May Surprise You
Published: March 06, 2015
Photo courtesy of MarvistaVet

(Editor's note: Not all veterinarians agree that spaying cats at this age decreases the cat population. Talk to your veterinarian about your pet.)

There is a thoughtful new movement designed to get to the next and final phase of ending domestic annual over production of kittens. The over-production problem is becoming known in animal shelters as the kitten tsunami, which occurs each late spring/early summer. 

The solution is preventing successful winter mating season through timely sterilization.  I will not recount the number of advantages of feline sterilization (spay/neuter.)  Most reading this already know them.  But what is not generally known is the female feline reproductive cycle.  That cycle, when understood, is the driving force behind the spay by 4 or 5 months of age championed by several profile groups.

Caring pet providers, who do not want to allow the nearly inevitable unplanned and unwanted pregnancy to occur, must request the fail-safe spay before the predictable breeding season arrives.  That means all moms of this past year and all new potential queens by 5 months of age should have their once-in-a-lifetime sterilization surgery.

December 21: Winter begins (the shortest day of the year)
Each day becomes a little longer. The longer day triggers the process called estrous (heat). Some queens will exhibit signs of estrous from as early as late January. Certainly by mid-February queens 5 months or older may be ready for a tom.

The clock starts. Once bred it is:
2 months gestation = birth
2 months nursing = weaning
+3 months = kittens maturing
5 months of age (August/Sept.)

March 20: Spring begins
Birthing begins with a few litters then crescendos with activity.  Cats are in heat, pregnant, (with short rest between heats) or nursing.  Peak time here is May, June and July: shelter kitten tsunami, considering the weaning time is around 8 weeks (2 months) of age.

June 21: Summer begins (The longest day of the year)
At this time of year the days are getting shorter.  Estrous is easing with a lot of overlap here.  A number of surprised caregivers are now scheduling spays though the damage is already done.  The “oops” (unplanned) litters are often now a problem.  What is to become of all those kittens.  Moms should be spayed 2 to 3 weeks after weaning or when the breasts have receded.

September 23: Fall begins
The days are now short enough that estrous (heat) is pretty much on seasonal hold.  Peace generally prevails and by mid-October estrous is down to zero. This year’s kittens are on the edge and not likely to be signaled into estrous. Even female kittens in February will probably not go into estrous this year, but all females this year will do so this upcoming breeding season. Spay by 5 months before winter solstice.

Note: The best holiday gift for your cat is a trip to the veterinarian for neutering (whether male or female.)

Let's put this basic nature's plan for cats into an organized and useful outline.  Let's start with all queens in the non-sexually active state = December.   December 21st is the start of the winter season, marking the shortest day of the year with each succeeding day becoming longer.  The incremental increasing lengths of daylight that begin after December 21st are being received through the eye and sent by the queen's optic nerve to signal this fact to the pituitary gland which, in turn, makes a hormone signaling the ovary that it's time to make follicles.  Pretty amazing.  The follicles, of course, make the eggs and estrogen.  It is the estrogen that makes the queen into what we see: a vocal tom-seeking maniac. The mating season is on! The toms, of course, are always ready and willing to serve.  This magical time will begin toward the end of January and becomes full blown by mid-February.  The domestic queen is an induced ovulator, meaning, when copulation takes place the severe stimulation of the mating process causes the follicles to rupture.  The eggs and estrogen are then released.  Now, two things are certain: she goes out of heat and there is guaranteed timing in which the sperm finds eggs.  Thus begins 61 - 63 days of gestation.

So now let's look at the next season (spring, March 20th begins the gestation/delivery/ nursing season).  By this time all unspayed queens are in various stages of the active breeding cycle.  Early estrous queens who mated in January will be delivering their litters starting in mid-March.  This is followed by a crescendo of successful matings resulting in more and more females who will be delivering.  There are those queens who were kept under house arrest and avoided the male encounter.  However, felines not mated often restart estrous within a few weeks for round two. Whenever a queen mates, it is 61-63 days later that an average of 3 to 5 kittens are born.  Then 2 months (8-9 weeks) later, the kittens are weaning and the caretaker may decide to keep them or try to re-home them.  If unsuccessful, ultimately the heart wrenching decision is made to take them to the shelter.  Shelters call May, June, and July the kitten tsunami season as there are multiple litters arriving per day.  Of course, while kittens are nursing and growing they are a delight to watch.  Their placement two months after delivery now becomes an acute dilemma for shelters. 

Days begin shortening on June 21st, which is also the first day of summer, and there are kittens and cats of all stages and ages.  Some queens will get pregnant a second time.  With house arrest or just luck the first estrous will subside but if mating did not occur, the female's heat will restart and toms have had a second chance.  If she appears out of heat it could well be she is actually pregnant in which case, of course, the queen will soon look pregnant (distended abdomen).

The traditional calendar reports September 23rd as the beginning of fall season.  Pretty much by the end of August, cycling (periods of heat) has stopped.  Closure proceeds normally for the development of the last of this past year's nursing and weaning.  Thus, fall is a blessed period of general feline tranquility until the next winter breeding season begins.  Kittens are growing and moms gain weight back.

So there's the basic outline of what and when the forces of nature make the queens (young and older) do what they do.  Personal experiences may differ somewhat but this outline encompasses the vast majority of them.  Some obvious factors may change some of the timing; e.g.; caretakers in the southerly states are going to recognize this pattern; northern states may find the seasons are shorter; whereas in Hawaii the season is almost year round kitten time.  Indoor cats with artificial lighting can have their heat cycles affected by their caretakers' personal use of lighting.

Armed with those time frames and the combination of age at a given season we know that young queens can come into estrous as early as 4 to 5 months and for sure by 6 months.  This means spaying by 5 months is good insurance against "oops" litters.   A little thing like "I forgot to make an appointment" or simple procrastination can happen far too easily in our busy lives.

What is absolute is that any of the female kittens born into any year's reproductive cycle will be more than ready to respond to nature's wake-up call by the winter's increasing daylight.  There is plenty of evidence that unintended litters are born simply because the queens were not spayed.  Don't let your charge be one who adds to the kitten tsunami.

The sheer number of veterinarians who sterilize cats younger than 6 months and the reported ease of surgery, safety and rapid recovery makes spaying at 4 or 5 months of age a sound practice.  By performing surgery by 5 months and eliminating all of the "oops" litters, the overbirthing could theoretically be eliminated in one or two years.  What a triumph that would be for all concerned.

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