The human woman, we all know, is pregnant for 9 months. But how long is a cat pregnant for? How long is a dog pregnant for? How about a horse? What is the longest pregnancy? What is the shortest? Let’s look at some common animals, as well as some uncommon ones.
Gestation is just the act of carrying a single embryo. If there are multiple embryos in one pregnancy, there are multiple gestations.
Let’s start with us. Humans are pregnant for nine months, or 280 days, give or take. The longest pregnancy on record is Mrs. Beulah Hunter, as recorded in a Times article in 1945, saying she was pregnant for 317 days. Today, most doubt that claim, saying the placenta just won’t support that long a pregnancy. They say she just had a miscarriage and immediately became pregnant again.
A cat is pregnant for about 65 days. In the case of a cat, multiple fathers are possible. A cat's eggs are fertile for 24 hours. If the cat has sex several times during the 24 hours, she can get pregnant by more than one male. Also, she can go into heat within days of giving birth, and get pregnant again!
All breeds of dog are pregnant for about 62 days. Dogs come into heat about twice a year. Average litters will yield 6 puppies, although this can vary depending on the size of the dogs. Toy breeds will have 1-4 in a little, while large breeds can average as many as 14.
Horse and Donkey
Horse can get pregnant once a year and usually in mid to late spring. Their offspring are born 11 months, or 320 days, later. It is to the advantage of a thoroughbred to have been born as close to January 1 in the new year as possible, so breeders will use lights to fool the cycle of the horse into going into heat sooner to try to time the birth. Donkey pregnancies can vary from 11-14 months. Their conception rate is lower than the 60-65 percent rate of horses, but they have more chance of having twins.
Whales and Dolphins
Dolphin gestation periods will vary depending on the species. Some last only 11-12 months, with the Orca having the longest at 17 months. Frequency of calving also varies depending on the species, from every 3 years up to every 8 years.
With whales the rates can vary also. They will usually be between 13 and 19 months, with the Sperm Whale getting the prize for the longest at 19 months. There is usually 2 years between their pregnancies.
Dogfish Sharks gestation can last up to 24 months, although a couple of species of sharks may have longer pregnancies. There just is no data on them. Remember, sharks are fish, not mammals, so their gestation are a little different. Some sharks lay eggs outside the female, and these just take their chances, they are not guarded by either parent. Some lay the eggs inside the female, and the first-born will eat the unhatched eggs for nourishment. There are also some observances of pregnancies without male fertilization of the eggs.
The female elephant will get pregnant when she is 10-13 year old. Elephants can have pregnancies lasting 22 months. The female will have a pup roughly every 5 years, and she can do so until she is 55-60 years old. The male may have to wait until he is 30 before becoming a father, depending on the hierarchy of the herd.
I guess the longest pregnancy, though, goes not to a mammal, but to an amphibian. The Pine Black Salamander living in the Alps can have pregnancies lasting up to 38 months, depending on the altitude she is at.
We have all heard about the fast breeding of rabbits. Rabbits are pregnant for 30 days. But their mating season is 9 months long. The females are ready to breed at 6 months old. This means that a single mother can have up to 800 descendants in a single season.
Marsupials have the shortest gestational periods, coming in a 12-13 days. But they cheat a little. The children are born prematurely, then they are nursed in pouches, close to the mother’s abdomen.
The human female pregnancy of 9 months can definitely be uncomfortable and tedious, but all species have their downsides to go with their pregnancies as will. Gestations lasting up to 3 years? Carrying the baby in a pouch by your stomach? 800 descendants in a year? Pregnant again 2 days after giving birth? I guess you get used to what you are given but I don’t think I would want to trade with another species.