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We will start with the mating. When the male is ready to mate (which most males pretty much always are!) Once mature enough (about one year) - just waiting for the signal from the female) he may make a cooing, chuckling noise and both sexes may rub their chins on the floor. Also the male may do what I like to call The swish swish dance (where the male gets down low swishes his tail back forth and cooing at the female). Mating usually takes place at night when it dark, but more often it also can be observed in the evening or the early morning hours. Following what often becomes an all night romp you will often find bunches of fur and perhaps the "mating plug". This is a waxy plug, larger then the "estrus plug", about 1 1/2 inches long. You rarely find the plug, because they usually eat it or you throw it out when you clean the cage out.
After mating males are very careful about cleaning the penis after each mating, but due to the often large amount of hair loss during mating it can be hard for him to remove all of the fur after mating the male should be checked for the presence of a hair ring. Mostly loose fur that can accumulate inside the penile sheath,even when not mating males should be checked for a hair ring about every month. This can create a ring of fur that will act as a constricting band around the penis resulting in pain, difficulty urinating, and eventually prolapse, swelling, and damage of the entrapped organ. This can lead to excessive grooming which leads to further damage. If hair rings are present the penis should be gently lubricated with petroleum jelly. The hair ring should then be carefully teased open and cut off (VERY CAREFULLY) with fine scissors.
Here is a picture of Delia and Sampson mating. Sorry for the bars, but I did not want to disturb them.
Pregnancy in a chinchilla can be hard to detect especially during the first 2 months. If your female is not used to being handled its best to leave her alone if you suspect she is pregnant. Stress can cause her to abort the kits. If your female is used to your affection and seems to want to continue to be outside of the cage it is alright to hold her. Or if not you can just put your hand under her belly and feel if it's hard or if you feel some kicking. Just be sure to take lots of extra care. Many females will go through mood swings during pregnancy. Some of my usually friendly females will begin spraying urine at me when they are pregnant. Other females that shy away from my hand will become more affectionate during those 111 days. Pay attention to your animal’s wishes and honor them.
After the 90 day mark you may notice your female’s nipples getting redder and longer. She has six nipples, three on each side. You can locate them by placing your hand under her “armpit” and running it down her belly in a straight line. Before pregnancy and during the first months the nipples will be small “bumps” and very hard to locate. By delivery they will be almost as long as her hair. You will also notice that she is gaining weight and her belly is rounder and firmer. First time mothers usually have smaller babies and many times have single births. These can be harder to detect. Chinchillas carrying multiple kits will be obviously large. As the female gets closer to her delivery date you may be able to see the babies move.
Here let’s look at the development of a chinchilla during the 111 days of pregnancy. The information and pictures below are based on an article written by H.H. Greenlee, D.V.M.
At 30 days it weights .1 gram
At 45 days it weights 1 gram
At 60 days it weights 10 grams
At 80 days it weights 25 grams
At 100 days it weights 40 grams
At 111 days it weights 45 grams
Finally we arrive at the day of delivery. The average length of pregnancy is 111 days however some chinchillas will deliver early and others will go a bit later. The majority of chinchillas will birth their babies during the early morning hours but they can deliver any time of day. Birth is a very natural thing and your female should be able to handle everything on her own. When she is in active labor you may notice her huddled up in an awkward position. She may bend down to check the process from time to time as she begins pushing the baby out. Once the baby is delivered, she will clean it a little and may sit on it to let it nurse. If she is giving birth to multiple babies she will go back into labor again. It’s not uncommon for babies to come out as much as 45 minutes apart. When the mother is delivering the next kit, the first of the litter is left alone and wet so it is important that the room be a comfortable temperature with no cool drafts. Once all of the babies are delivered the mother should tuck the babies under her and keep them warm as they dry. She will have delivered an afterbirth, (the placenta that held the baby) for each baby she delivered which should be removed from the cage. Many chinchillas will nibble at the afterbirth, which is rich in protein, but they should not be permitted to eat the entire thing.
It’s important to know that the female will go back in heat after delivery and will mate with a male sometime within the next 72 hours if he is not removed from the cage. I prefer not to let my females breed again right after delivery; however this is a common practice for many breeders. During this next mating, newborn kits can easily be trampled and killed. If you choose let them breed again right away, it is important to place a small can or box in the cage where the babies can hide and be safe. Before allowing this breed-back it’s important to remember what is going on during pregnancy. With a new litter of chinchillas, the female is providing lots of milk which requires minerals, fats, and proteins to be pulled from her body. If she is pregnant again she also has to supply nutrients to the growing embryo. Looking back at the growth chart above you will notice a gradual growth up until about the 60th day and then rapid growth begins. The drain on the mother during the rest of her pregnancy is intense. There is a lot going on inside her as the babies bones begin to harden, hair begins to grow, and muscles are strengthening. If the mother is still nursing kits during this point in her pregnancy she may become run down as her body works to provide for the needs of all of her kits. For this reason it is best to wean her kits at 8 weeks to give her body the ability to provide everything the new babies need to be born healthy. Once the next litter is born she should be given a long resting period with no matings to give her body time to recover.