What Are the Patterns of Estrus in Female Foxes? A Detailed Explanation

During the resting period, the vulva of a female fox is covered by pubic hair, making it hard to detect; during estrus, the pubic hair parts only because the vulva becomes swollen. The estrus period of female foxes is short, mating is relatively difficult, and the optimal timing for mating is also hard to determine; in particular, silver-black foxes have a relatively high rate of failed conception. To improve the reproduction rate, it is necessary to understand the estrus patterns of female foxes and mate or perform artificial insemination at the right time.

The estrus period of female foxes can be divided into three stages:

Stage one: the vulva begins to swell, the clitoris enlarges, and the female begins to show signs of attraction to males and sexual excitement; this generally lasts 2 to 3 days, and in some cases 6 to 7 days.

Stage two: the vulva of the female fox in estrus becomes noticeably swollen, almost circular in shape, and the clitoris of the blue fox turns red; this stage lasts 1 to 2 days in silver-black foxes and 2 to 3 days in blue foxes. The female fox's sexual excitement becomes stronger, and she actively approaches the male fox.

Stage three (also called the mating period): this is the period when the female fox accepts mating; the vulva becomes oval-shaped, everts, loses elasticity, darkens in color, and secretes mucus. This stage lasts 2 to 3 days in silver-black foxes and 3 to 5 days in blue foxes. For the entire duration of estrus in female foxes, silver-black foxes last 5 to 10 days, with the mating period lasting 2 to 3 days; blue foxes last 9 to 14 days, with the mating period lasting 3 to 5 days.

In stage three, the female fox is very excited, chases the male fox, raises her tail to one side, and accepts the male fox mounting and mating. In young female foxes, the changes in the external genitalia are usually not very obvious, and the entire estrus duration is longer than that of females that have given birth before.

The following three methods can be used to identify estrus in foxes:

(1) Examination of the external genital organs: the vagina is swollen, everted, pink or dark red, the clitoris is exposed, and white or yellow mucus is secreted; this already indicates that the female fox has reached the mating period, and she should be paired for breeding or inseminated for 2 to 3 consecutive days; if the vulva contracts, the swelling subsides, and secretions decrease, it is the late stage of estrus or estrus has already ended.

(2) Observing sexual behavior from the outside: when a female fox is in estrus, her appetite decreases, or she does not eat feed, she is restless, walks back and forth in the cage, and urinates more frequently; when the mating period arrives, the female fox becomes extremely restless and continuously makes urgent courtship calls; this is exactly the time for pairing and breeding. Only in the late stage of estrus does the female fox's activity gradually return to normal.

(3) Pairing for test mating: during the breeding period, in order to improve the mating rate and conception rate, in addition to examining the external genitalia and observing sexual behavior, test mating should also be carried out at regular intervals; this is especially useful for young female foxes whose estrus is not obvious, as it can avoid missed mating and also stimulate the female fox to enter estrus earlier.