Chinchillas are seasonal breeders. This means that they do not reproduce year-round. This seasonality is due to the female's estrous cycle, because males remain fertile year-round. In the southern hemisphere, where chinchillas originated, they breed from May to November. In the northern hemisphere, their reproductive cycle is shifted six months to accommodate the difference in seasons, light cycle, and climate, and they breed from November to May. Although female chinchillas ovulate (release eggs from the ovaries) about once a month (every 38 days), they usually produce only two litters a year.
Female animals are generally classified into two groups. Spontaneous ovulators are animals that ovulate spontaneously, whether mated or not. (Examples include hamsters and mice.) Induced ovulators are animals that ovulate in response to mating. (Examples include cats, ferrets, and rabbits.) Chinchillas are unusual in that they are a blend of both. Most chinchillas ovulate spontaneously, but they will also ovulate in response to being mated.
Estrus
Estrus is the time during the breeding season, just before and just after ovulation, during which the female will permit the male to mate with her. Estrus in the chinchilla usually lasts from 12 hours to two days.
It is characterized by a change in color around the perineal area from pink to deep red. Swelling of the vulva does not usually occur, although the reddened tissue may make it appear that way.
As a chinchilla breeder, you need to observe your animals closely, particularly during the breeding season. This will allow you to know when to put the female and male together and make plans for the litter well in advance of the birth.
Puberty
Unlike many rodents, chinchillas take a long time to reach sexual maturity. They may reach puberty as early as five and a half months of age, but the average is about eight months of age. Male chinchillas are usually smaller than the females and need extra time to attain the size and physical development to be able to breed successfully. However, they may produce sperm as early as two months of age.
Courtship Behavior
During the breeding season, the male chinchilla will initiate courtship by grooming the female. As the courting ritual continues, the male will attempt to mount the female. If she is not yet receptive, her behavior can be unpredictable. Females can be very aggressive toward males, even during estrus. It is extremely rare, though, for a male to fight back or even attempt to protect himself other than to run away in panic from the female. So you must closely supervise the animals to make sure the female does not harm the male. Some females are so much larger, stronger, and aggressive than the males that they have been known to kill the males, especially if the males have no way to escape from them.
Several breedings may take place at intervals, but all take place quickly, probably as an antipredator defense mechanism. If breeding took too long, chinchillas would be vulnerable to predators in the area.
Ovulation
Ovulation is the release of eggs from the ovaries. Assuming the male is fertile, the number of young conceived will depend upon the number of viable (live, healthy) eggs released during ovulation. Litter size ranges from one to six, with an average of two.
Implantation
Implantation, the attachment of the embryo to the uterus, takes place in the chinchilla at five days after mating. The placenta is an organ that is part of the baby and not of the mother. Each individual fetus has a placenta of its own. The placenta attaches each kit to the mother's uterus so that it can receive nutrition through the blood supply. Different animal species have different kinds of placentation. Chinchillas have a chorioallantoic-type placentation.
Even though embryos may attach to the uterus, things can go wrong and pregnancies may not be carried to term, or completion. Fetal reabsorption is common in chinchillas at any stage of their pregnancy and is observed more often than fetal mummification or abortion.
Pregnancy
The time during which the female is pregnant, that is, from conception to birth, is called gestation. The 111-day (105- to 118-day range) gestation period in the chinchilla is very long compared with most rodents. Chinchilla fetuses grow more slowly than most rodent fetuses of closely related species.
Usually a long gestation means the offspring are born precocious, that is, well developed and fully able to fend for themselves. Although chinchillas are born with fur and their eyes open, they still need their mother for protection and nutrition for at least six to eight weeks.
An interesting theory has been postulated to account for long gestation periods in some hystricomorph rodents such as the chinchilla. It suggests that species with long life spans and long reproductive periods have large brains at birth and in adulthood and that the gestation length is determined by the brain weight and stage of development at birth.
If your chinchilla is carrying several young, you will probably detect an increase in size in her abdomen during the last month of her pregnancy, and when you pick her up you may notice she feels heavier. You should weigh her weekly to keep track of any unusual fluctuations in body weight that could signal a problem.
Handle your pregnant chinchilla carefully and gently so the unborn babies are not crushed or injured. Do not grasp the mother-to-be too firmly around her abdomen. Support her body when you hold her. Do not make changes in her cage that might upset her. Make sure newspaper or soft bedding is on the cage floor so that when the kits are born they cannot catch their small feet and limbs in the wire mesh cage floor.
Birth (Partuition)
Birth usually takes place in the morning hours. Chinchillas give birth by sitting up and hunching over, or squatting. Kits are usually born a few minutes apart, although the time interval between kits can be as long as an hour. Some kits are born head first, others may be born breech (hind limbs and rump first). The placenta passes shortly after the kits. There should be one placenta for each kit. It is normal for the mother to eat the placenta.
If your chinchilla has been in labor for more than an hour, if the kit is partway through the birth canal and the mother is unable to pass it, or if the placentas have not passed, contact your veterinarian immediately.
Kits weigh about 2 ounces (60 g) at birth, although they may be as small as 1 ounce (30 g). During the birth process and afterward, the mother and her babies may chirp softly to one another. If you listen closely, you will recognize these tender sounds as the announcement of the birth of a new litter!
Chinchilla parents are very protective of their young. It is unlikely, but possible, that the mother will bite you if you reach into the cage, so be careful! Be sensitive to her feelings. If she is upset, she will growl or snarl. If she is very fearful, she will make the eek eek cry. During the first few hours after birth, it is best to leave the new family alone.
Mortality can be as high as 10 percent at birth. When it doubt, do not hesitate to contact your veterinarian for help.
Soon after birth, the female chinchilla will come into estrus again. This is called a postpartum estrus. This early estrus is not uncommon in rodent species. If your chinchilla does not breed and conceive on the postpartum estrus, she may return to estrus again (postlactation estrus) when the kits are weaned. If bred, she could conceive at that time.
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