Female gerbils can become pregnant when there are no males around. Or, a gerbil that was thought to be male will give birth. If this happens to you, you may wonder if gerbils can change sex.
Gerbils can’t change their gender. A gerbil’s sex is permanent, and determined at the moment of conception. Female gerbils have two X chromosomes, and males have XY chromosomes. If your gerbil has babies unexpectedly, it may have been pregnant when you bought it. If not, it means that one of your other gerbils is male, and was mis-sexed.
We’ll look into whether gerbils can change sex, and how to tell a gerbil’s gender. We’ll discuss whether gerbils can be born pregnant. We’ll also explore the reasons why two male gerbils might try to mate.
Can Gerbils Change Sexes?
Some species of animal can change sex, from male to female or female to male. This is known as sequential hermaphroditism.
In some fish, a female leads the group. When she dies, the next highest-ranking male will change sex to female and take her place.
Female animals can also turn into males. According to Live Science, chickens can change from female to male if their ovaries stop working.
But gerbils do not share this ability. Gerbils aren’t hermaphrodites, and gerbils can’t change from one sex to another. Whatever sex a gerbil is born as is the sex it will remain for the rest of its life.
Female gerbils are conceived when the mother’s egg is fertilized by a sperm carrying an X chromosome. A male gerbil is born if a sperm with a Y chromosome reaches the egg first.
The mother’s egg contains an X chromosome itself. So, female gerbils are XX, whereas males are XY. This is the same as most other mammals, including ourselves.
Gerbils reproduce sexually, so a female gerbil must mate with a male to have pups. Only female gerbils can bear young, and only male gerbils can fertilize a female’s eggs.
Can Rodents Change Gender?
Scientists haven’t found any evidence that rodents can change gender. All rodents, including gerbils, are dioecious. This means that every rodent is born either male or female, and their sex is permanent.
Researchers in Science found that male mice could be turned into females by cutting out parts of their DNA. But this could never happen outside of the laboratory.
Male and female gerbils look almost identical, so it’s easy to mistake one for the other. That’s why you might think your male gerbil has had babies, or your female gerbil has become pregnant spontaneously.
Male gerbils can’t get pregnant. So if your ‘male’ gerbil has had a surprise litter, it’s really female. You were either told the wrong gender when you bought it, or you misidentified its sex yourself.
Female gerbils can’t get pregnant without having mated. So, if your gerbil has fallen pregnant, she must have come into contact with a male. Either this happened at the pet store, or one of your other gerbils is male.
Is My Gerbil a Boy or Girl?
When you get a gerbil from a breeder or pet store, they will tell you its sex. But sometimes, they get it wrong. It’s common for gerbil owners to discover that their ‘male’ gerbil is female, or vice versa.
This is because gerbils don’t exhibit much sexual dimorphism. In other words, it’s difficult to tell a gerbil’s gender just by looking at it.
Sexual dimorphism is the scientific term for when the male of a species looks different to the female. For example, males and females of some animals are different colors.
Male gerbils and female gerbils look almost identical. The only difference is the size. Male gerbils are typically bigger than females.
But this difference is only obvious in adult gerbils. It’s also not always true, as genetics and diet can affect how a gerbil grows. For this reason, size is not a reliable indicator of a gerbil’s sex.
Often, a gerbil owner won’t realize their gerbil has been incorrectly sexed until the female becomes pregnant. You can try to ‘sex’ your gerbil yourself, by looking underneath its tail.
How to Sex a Gerbil
The only trustworthy way of sexing a gerbil is to examine its genitals:
- Place your gerbil on a flat surface, facing away from you. If it doesn’t want to sit still, you can hold your gerbil in your hand.
- Carefully lift up your gerbil’s tail with your spare hand, and take a look at its rear end.
- If your gerbil is male, you will see a large gap between the anal and urinary opening. It looks like a vertical line. Females have a much smaller gap — the vagina and anus are right next to each other.
- In a male gerbil, you may also see a bulge at the base of the tail. This is where the testes are, underneath the skin. However, if your gerbil is young, this may not be easy to see.
It’s tricky to sex gerbils, especially if you’ve never done it before. A gerbil’s genitals are small and hard to see, and they don’t like to sit still.
If you’re not sure what you’re looking at, the best way is to compare two gerbils. If their genital areas look the same, they’re probably the same sex. You can also take your gerbils to a veterinarian for an examination.
Can Gerbils Be Born Pregnant?
If your gerbil is expecting, and you don’t have any male gerbils, you may think she was born pregnant. But this is impossible.
Some female animals can reproduce without mating with a male. This is called parthenogenesis. It has been observed in some reptiles, fish, and insects. According to Current Biology, most female aphids are born pregnant.
But parthenogenesis doesn’t happen in mammals. A gerbil embryo can’t develop unless it has DNA from both a male and a female.
Female gerbils can’t be born pregnant — they need to mate to have babies. If your gerbil has got pregnant without any male gerbils around, one of two things has happened.
Your gerbil may have mated with a male while she was still in the pet store. According to Developmental Psychobiology, female gerbils can get pregnant from as young as 9 weeks of age. If the pet store employees didn’t separate the litter at an early age, this is likely what happened.
pregnancies last around 25 days. So if your gerbil gives birth less than a
month after you bought her, she was already pregnant.
If not, the only explanation is that she mated with one of your other gerbils. That means that one of your ‘female’ gerbils is really male.
If you suspect that this is the case, separate your gerbils right away. Otherwise, you may end up with two litters. Gerbils can get pregnant again the same day that they give birth.
Why Are Two Male Gerbils Trying to Mate?
If two male gerbils live together, you may occasionally see one ‘mounting’ the other. When this happens, you might wonder if one of your gerbils has changed sex.
Male gerbils can’t turn into females. So if your male gerbils are truly mating, one of them was mis-sexed in the first place.
During mating, the female gerbil will willingly present herself to the male. He will mount her several times over a few hours. They will each examine their undersides afterwards. This may be accompanied by foot thumping.
Once two gerbils have copulated, the female will give birth in around 25 days. So, if one of your gerbils is female, you’ll find out in less than a month.
However, sometimes, a male gerbil will mount another male as a way of asserting dominance. This looks different to real mating.
Dominant Male Gerbils Mounting
Gerbils that live in pairs or groups establish a complex social hierarchy. There is always one ‘leader’ gerbil that is in charge of the others.
The dominant gerbil is usually the biggest male. He gets to have the first pick of the females, and first choice of food.
Over time, other gerbils may challenge the dominant male for his place in the clan. To avoid losing his position, the top gerbil will display dominance behaviors such as:
- Grooming the subordinate gerbils
- Scent-marking the enclosure
- Preventing the other gerbils from doing things, such as eating
- Chasing or fighting with the submissive gerbils
- Mounting the other gerbils
When mounting for dominance, the submissive male will not present himself to the male. The dominant male may have to chase the other. The subordinate will usually try to get away while being mounted.
Mounting is normal behavior, and it won’t hurt the subordinate gerbil. But if he doesn’t accept the other gerbil’s display of dominance, the gerbils may fight. You should separate fighting gerbils straight away, so they don’t injure one another.