General Breeding Practices
The Average Chinchilla | Housing | Temperature | Environment
Females will give birth between 106 and 118 days from the time of fertilization. Average is around 111, mine have varied depending on how many kits are being carried and the stress level of the mother.
It can take a few minutes to several hours for a chinchilla to give birth once she starts contracting. Average is 5-10 minutes between kits, but I have seen them born much more quickly, and several hours apart. Occasionally a fetus is retained; those will usually pass within a week and you will find them in the cage. You may find a hard, dime-sized ball after she has given birth; this is a partially reabsorbed fetus. If the female does not give birth, she may reabsorb the kits and be at a high risk of infection. After a month, the full sized kits are down to quarter sized, and are completely gone by 3 months. You will notice the female is very sickly during this time. The female will then be capable of breeding again. On rare occasions, the female never goes into labor, and will have a constant cycle of getting pregnant and reabsorbing kits.
Breed backs and estrus;
Chins come into heat around the time of birth. Some 2-4 days before, others up to 13 days afterwards. If it is spring, a female will come in 30 days after having kits. In the fall and winter it could be up to 90 days depending on your light source. If a female takes during a breed back, she can have up to 3 litters a year. If you use a natural light source females generally will not breed between the months of October and December. Below is text quoted from Growth and Reproduction of the Chinchilla by Jikken Dobutsu; "Eighty-one out of 123 litters were born between March and August during 3 years, and parturition never occurs in December. The most suitable season for reproduction of chinchillas may be from January to April, and a summer anoestrous seems to be present in August to early September as reported by Weir."
If your lights are on a timer (I set mine for 12 hours), chins will breed year round.
Litters range between one and seven kits, with two to three being the norm. Litter sizes tend to run in family lines, but can also be determined by health and bodyweight. Too little body fat, and the female will not ovulate. Too much, and it will build up in the vaginal tract and make birthing difficult, or the female will never take. Size tends to be related to litter quantity. In general, the larger, (fatter), blocky-type chins tend to only have one kit per litter, rarely two. The smaller, narrower chinchillas have been known to have up to six and seven kits. It is commonly noticed that a female that produces 3-4 offspring, when bred with a male out of a high producing line, will throw offspring that produce well, and visa versa with large, single-littering females.
Baby birth weight varies drastically. My births have ranged between 28g and 68g, with the average being 48.2g. I have heard of one born at 112g, and that was from the 1133g chinchilla mentioned below. A fellow breeder regularly had births between 60 and 80g, but also had a high kit mortality rate. Whether or not those were related I don't know, as they got out of breeding. Generally you will see kits born 2-6g apart in weight, for example; 45g, 48g, 52g. Occasionally you will get two large kits and one really small (20g range). The smaller ones tend to die in the first few days.
It is a good idea to check the pelvis size on females. It should be at least a dime in width, and a dime and a half in length. This is big enough to fit the flat of your thumb in, for someone with smaller hands. To check the pelvis size, you hold the chinchilla by the base of the tail, with your thumb on the bottom facing the uterus.
The Average Chinchilla;
Tends to weigh around 600g, and is generally wedge shaped. The smallest adult I've owned was 390g at adult weight, largest was 1,133g. A good breeding animal should be over 650g and have clear, dense fur. It is desirable for them to "look like a brick" from the top down, but overall, shape will be overlooked for clarity, color and density.
In the last few years, big, blocky animals have become the rage. People want as big as possible; 800, 900, and 1,000+ gram animals. As noted above in the litter size section, larger animals tend not to produce as well as the smaller animals, and therefore tend to be harder to find.
Some colors tend to run small, extra-dark ebonies/ebony crosses, sapphire blends, and violets, though I have seen a huge upturn in violet size the last couple years. I have photos of an 880g Tov violet female in the colors section.
There are two styles of housing, runs and colony cages. Whatever you chose, I recommend it be no taller than 18" for kits as they can climb the day they are born. They aren't terribly talented, and like to shoot up to the top and let go. The spacing on the cage wire needs to be 1" x 1/2" or smaller. Rabbit style breeding cages where the mesh is smaller on the bottom and larger on the top are not good. They will still climb and get through the holes at the top.
If you go with runs and don't want a breed back, you'll need to close dad off a couple weeks before the kits are born. If you want him to breed mom right away you will need to close him off 4-5 days afterwards or the kits may get into the runs and be killed by another female. It isn't uncommon for kits to be trampled to death during a breed back, many breeders place soup cans on their sides in the cage for the kits to get into.
With colony breeding, you'll need to watch them carefully. Females will fight over the kits or get aggressive towards anything and everything if the male tries to breed them too. This can start some bloody fights, even in colonies that have been together for a long time. If you've got a close knit colony, all of the females tend to give birth together and will take turns caring for the kits.
In my experience, a breeding herd breeds more consistently when kept between 52 and 68 degrees. Any warmer and the litters drop off. I've never had a room get cooler than 52, but I imagine you would need to start providing heated nesting boxes to keep the babies from freezing when born.
Above 70, females will still breed, but will be in much poorer body condition. Chins exert a lot of energy to keep themselves cool, and I have seen them regulate a 12" x 10" box to 75 when the outside temperature is 85 or more. They tend to lose bodyweight doing this, and need a higher caloric intake. Note that the animals had been acclimated to the slowly rising temperatures all spring. They remained active and alert at night, even when the temperatures were still in the 80's.
That said, I recommend keeping your chinchilla below 75 degrees at all times. Sudden bursts of heat when kept at cooler temperatures will cause heat stroke.
Environment plays a huge factor in the health and well being of your herd. A poor environment will produce fewer kits and the chinchillas will be in poor body condition.
Things that make a good environment are; consistency in temperature, feeding, cleaning, watering, no sudden noises, good air circulation and cool (60 degrees). If you have a very stable environment and change one of those things you will notice a weight drop, or they will go off of feed immediately. Many people like to keep chins in a bedroom in the house, but forget that houses make a lot of strange noises. Chins do not like the same company you do; new visitors, new smells, new noises... they can adjust, but it takes a month or more. I see radios in every herd I've visited; this is to partially down out the outside noise, and get chinchillas used to noises that humans make. Most have fans to circulate the air, and feed and clean on a regimented schedule.
This isn't to say you can't keep a pair in a high traffic area, like your kitchen, we did. They got used to the things we did and liked to watch us go about our lives. They did not like changes outside of our routines, like guests, dogs, children, or noisy new things.
*Growth and Reproduction of the Chinchilla courtesy of PubMed.