Rats, like other rodents, have developed a very successful and prolific reproductive strategy They are highly social animals, take care of each other of the others and, although the males do not have a highly developed parental care, the females do help each other to be able to raise all the young forward.
In this article on our site we will tell you how rats reproduce, what the reproductive cycles of males and females are like and how it is the development of the offspring after birth.
Sexual behavior and factors that affect
Sexual behavior appears during puberty Males reach this stage at 6 weeks of age and females between 6 and 8 weeks after birth. The behavior is dimorphic between females and males, that is, they have a different sexual behavior depending on the sex to which they belong. The males reproduce actively throughout their lives and, on the other hand, the females only accept to copulate when they are in heat or oestrus.
Sexual behavior is regulated by hormones and is affected by environmental factors:
Lightning
Female rats are annual polyestrous, that is, they can reproduce all year long if the right light conditions are given (12 hours light and 12 dark). In nature, during the winter months these conditions do not exist, so during this time the birth rate is very low. In captivity, domestic rats do reproduce throughout the year, without reducing the number of heats or offspring, as long as we provide them with adequate light/dark cycles.
If we talk about the rat as a pet, we must also take into account the intensity of the light, since high intensities can cause damage to the eyes, especially when it comes to albino rats.
Temperature
Small animals, such as rats, cannot withstand extreme temperatures, whether low or high. Due to the surface/volume ratio of their body, they poorly regulate these temperatures. In periods of the year when the temperature is very high or low, anestrus occurs in females and they will not go into heat, therefore, they will not reproduce.
Nutritional condition
During pregnancy an increase of certain components in the diet is necessary, but overfeeding is always harmful. It has been shown that caloric restriction before heat can improve fertility and possibly lengthen the reproductive life of the female. Vitamin deficiency can cause infertility, especially vitamins A, E, B2 and B1.
Presence or absence of the opposite sex
The presence of the opposite sex favors the appearance of sexual maturity. Instead, absence inhibits maturity, especially when there is a dominant male.
Pheromones
Pheromones are crucial in establishing relationships between rats. Not only do they mediate reproductive cycles, they also provide information about the hierarchy within the group, he alth status, fertility, etc.
Noises
Rats are very sensitive animals In the wild they may decide to leave the nest for a safer one but, in captivity, the noises and even strong odors (such as perfume) can cause high levels of stress, leading to oestrus suppression or cannibalism of offspring.
Overcrowding
Overcrowding only occurs in captive rats, therefore, we must ensure that we offer our pets a cage with adequate dimensions. If the rats are overcrowded, they will not reproduce, because the females will enter anoestrus.
Reproductive system and cycle of the male rat
The male rat reaches puberty when it is 6 weeks old, but will not reproduce until it is 10 or 11 weeks old, at this point, it will be able to reproduce for the rest of its life.
The reproductive system of male rats is very similar to that of other mammals. It consists of a penis, two testicles, the accessory glands and the ducts that carry the sperm to the outside. In the testicles, we find structures called the head, body and tail of the epididymis through which the developing sperm will pass as they mature and the seminiferous tubules, where the sperm are created.
The spermatogonia (male germ cells) are formed from cells in the seminiferous tubules of the testes. Each spermatogonia can produce up to 120 spermatozoa These spermatozoa develop during their passage through the epididymis, passing through several phases:
- Primary spermatocyte
- Secondary spermatocyte
- Spermatid
- Spermatozoon
Upon reaching the tail of the epididymis, the spermatozoa will be fully developed and, the ability to fertilize an ovum, is achieved by joining the seminal fluids produced by the accessory glands. This cycle of sperm creation and maturation lasts 13 weeks approximately.
As we said, the reproductive system of male rats is very similar to that of other mammals, with two exceptions:
- They have coagulation glands, which allow the coagulation of the ejaculated semen that blocks the entrance to the vagina, which is known as a plug vaginal.
- The prostate is double instead of simple, with a ventral and a dorsal area.
Reproductive system and cycle of the female rat
Like most quadrupedal females, they have bicornuate uteri (uterus with two horns) located on both sides of the abdomen. They also have two ovaries, a vagina, a clitoris and a vaginal entrance.
Females reach puberty between 6 and 8 weeks of age, but will not breed until 10 to 14 weeks. They are annual polyestrous, so they are in heat throughout the year and these last between 4 and 5 days. As in other mammals, the oestrus of rats consists of 4 phases: proestrus, estrus, metestrus and right-handed.
- Proestrus: lasts about 12 hours, the vulva is slightly thickened and the vagina is dry. It can accept the male, but fertilization will not occur.
- Estro: lasts 14 hours. The vulva is completely swollen (vulvar swelling) and the vagina is dry. She will accept the male and lordosis will occur, that is, the female will acquire a curved position of the spine. If there is copulation we can observe the vaginal plug, which serves as a reproductive strategy to prevent another male from trying to copulate with the female and thus ensure their own offspring. This plug dissolves naturally in less than 12 hours after intercourse.
- Metaestro: lasts for approximately 21 hours. The vulva begins to lose thickness. Ovulation occurs and the female will not accept the male.
- Destroy: This is the longest phase and lasts 65 hours. The vulva returns to its normal state and the vagina is moist. She does not accept the male.
If fertilization does not occur during the cycle, the female will undergo a pseudogestation, which will last between 12 and 14 days. If fertilization occurs, the gestation will last between 21 and 23 days.
Development of rats after birth
Female rats can have litters of between 6 and 15 pups The pups at birth are completely dependent on their mother, weighing about 3 or 5 grams, they are deaf and blind, pink and hairless. We can tell that they are newborn because there will be no milk in the stomach, in less than 12 hours after birth we will see a white color in the belly, it corresponds to a stomach full of milk.
When the hatchlings are 7 days old, their skin will begin to be covered by a fine, soft layer of hair. The ear canals begin to open and the ears separate from the head.
At about 2 weeks, they will open their eyes, some open them before others and they don't have to open both at the same time. At this age they will begin to investigate the nest, they will even be able to go out, although the mother will continually return them to the shelter.
From 21 days of age, puppies will weaningGradually, they will begin to eat solid food, gain independence and learn everything they need for adult life.
