What are the reproductive characteristics of the Ussuri raccoon dog?

1. Sexual maturity: Young raccoon dogs reach sexual maturity at 8-10 months of age, with males maturing slightly earlier than females.

2. Sexual cycle: The raccoon dog is an animal that comes into estrus once a year. The testes of the male begin developing from the autumn equinox, and by late January to early February the testes become soft in texture, mature sperm are present in the epididymis, sexual desire begins to show, and mating can take place. The entire mating period can last 60-90 days. After the mating period ends, the testes rapidly atrophy, returning to a resting state by May, until they develop again at the autumn equinox, showing an annual cyclical change. The sexual organ development of the female raccoon dog is similar to that of the male. The ovaries also roughly begin developing from the autumn equinox until late January to early February of the following year, when mature follicles and eggs are present in the ovaries. The entire estrus period lasts from early February to early April. After mating, a female raccoon dog that has conceived enters the gestation period and then the birthing and lactation period. Females that did not conceive and females that have been weaned return to the resting state, until the sexual organs develop again at the autumn equinox, showing an annual cyclical change.

3. Mating behavior: During estrus, the male raccoon dog actively approaches the female, sniffing her vulva. When the male raises a leg to mount the female, the female turns her tail to one side and stands still waiting for the male to mate. After the male mounts the female's back, his hindquarters shake frequently during mating, then his rump sinks, his forelimbs tightly clasp the female's waist, and he pauses quietly for 0.5-1 minute; a gentle fanning of the tail base indicates ejaculation. After ejaculation, the female turns her body to face the male belly-to-belly and remains lingering for a period (ranging from 1-30 minutes), then they separate, indicating successful mating. To ensure conception in the female, mating should be carried out once a day for 3 consecutive days.

4. Gestation: Counting from the first mating date, the gestation period of the raccoon dog is 54-65 days. Pregnant females become docile and calm, and their appetite increases day by day. At 25-30 days of gestation, the fetuses can be felt from outside the abdomen. By 40 days, the abdomen droops and movement becomes sluggish. Before giving birth, they pull fur to make a nest, curl up in the den, and are unwilling to go out and move about.

5. Birthing: They mostly give birth at night inside the den. Delivery lasts 4-8 hours, with some individuals taking 1-3 days. After each young raccoon dog is born at intervals of 10-15 minutes, the mother bites through the umbilical cord, eats the fetal membranes and placenta, licks the young dry, and only after all are born does she settle down to nurse. A few also give birth in batches over 2-3 days. The average litter size is 9, with a maximum of 18.

6. Mother-young behavior: Before giving birth, the female raccoon dog can pull out the fur around her mammary glands herself, exposing the nipples. She has a strong maternal instinct and does not leave the den after giving birth, nursing peacefully. Newborn young can crawl to find the nipples and suckle 1-2 hours after their fur dries. After feeding, they sleep soundly, generally suckling once every 6-8 hours. Young raccoon dogs grow teeth at 15-20 days of age and begin eating feed. At 45-60 days of age, they can be weaned and separated to live independently. At 5-6 months of age, they grow to adult size.