Seasonal changes are welcome, and if you are like many spring and summer are the most eagerly anticipated. For animal shelters and rescue groups spring is also the time when they become inundated and overwhelmed with litters of kittens. So what do the seasons have to do with it?

“Cats are seasonally polyestrous. This means they will have repeated heat cycles over a year unless they are bred, and the heat cycles are influenced by the seasons. The mating season in cats is determined by a number of factors, including the length of daylight, environmental temperature, and the presence of other cats.” – Pets.WebMD

Winter

Most people know the benefits of spaying, but the reason behind ensuring it is done before the spring kitten rush, may be less obvious.

The reason there are so many programs aimed at early spay/neuter of cats comes down to biology and understanding the female cats reproductive system. Animals 24-7 explains why winter can be a crucial time to ensure females are spayed, preventing “a successful winter mating season” and future litters.

“December the 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 (unspayed non-sexually active females) optic nerve signaling this fact to the pituitary gland which, in turn, makes a hormone signaling the ovary that it’s time to make follicles!”  Biology is cool and amazing.

The follicles = eggs and estrogen. Estrogen turns a queen into “a vocal tom-seeking maniac.” Let the games begin!

Cats are considered to be primarily induced ovulators, which means mating causes them to ovulate. A cat will continue to go into another heat cycle unless she breeds or the daylight factor takes over.

Spring

“Shelters call May, June and July the kitten tsunami season, as there are multiple litters arriving per day!” – Image Wikipedia

“March 20th begins the gestation/delivery/nursing season. By this time all unspayed queens are in various stages of the active breeding cycle. Queens who mated in January will be delivering their litters starting in mid-March.”

” It’ s 61-63 days later that an average of three to five kittens are born. Then, two months (8-9 weeks) later the kittens are weaning. “

Summer and Fall

Once the days start to shorten on June 21, the first day of summer, kittens and cats of all all ages abound and some queens will get pregnant a second time if given the opportunity.

“The traditional calendar reports September 23rd as the beginning of the fall season. Pretty much by the end of August, cycling (periods of a cats heat) has stopped. This means closure as the current kittens are weaned generally making fall a period of feline tranquility until the next winter breeding season begins.“

Depending on where cats reside this pattern can vary slightly, however the message will always be the same regardless of geography, and that is spaying female, and neutering male, cats early reduces the number of unwanted litters.