Fertility, Cycle, Ovulation, and Receptiveness to Mating

Unlike women or female dogs, female rabbits (does) do not have a fixed reproductive rhythm. Although there is some form of cycle, which is not well understood, it does not regulate their receptiveness to mating. Rabbits are not only fertile for a few days within each cycle, as their ovulation is triggered by external stimuli, such as another rabbit mounting them or intense petting. This makes rabbits highly prolific and hormonally focused on reproduction. The cycle and receptiveness to mating are also strongly influenced by the seasons.

Contraception Methods

To prevent unwanted offspring, rabbits in captivity are usually neutered. There are various methods for this procedure. Rabbits from shelters and responsible breeders are often already neutered before being rehomed.
Keeping multiple male rabbits (bucks) also requires neutering, as they can injure each other severely if not neutered. Neutering females is mainly necessary for medical reasons.

Early Neutering of Male Rabbits

When a male rabbit (buck) is neutered before reaching sexual maturity, it is called early neutering. Depending on the size of the rabbit, this is typically done at around 11-12 weeks of age, but at the latest by 16 weeks (for very large breeds). However, even large breeds can be neutered as early as 11-12 weeks.
In rabbits, the male is usually neutered to prevent offspring because the procedure is less invasive than for females.
Early neutering prevents the production of sexual hormones, meaning the rabbit will never fully mature sexually. However, studies show that early-neutered bucks do not face disadvantages in a group or hierarchical structure compared to neutered adults. In fact, they tend to be better socialized, as they do not need to be separated to prevent reproduction. This is the significant advantage of early neutering.
When a male rabbit is neutered before sexual maturity, he can be directly returned to his original group and continue to grow up there. Male rabbits neutered later remain fertile for up to four weeks after the procedure and need to be kept separated during this period to prevent reproduction.

Neutering Male Rabbits After Sexual Maturity

Neutering can be performed even in older rabbits as long as the animal is healthy and vital. However, sexual behavior impacts the rabbit’s position in the group and its overall character. In older, dominant rabbits living in groups, neutering can lead to a loss of rank, which can have a significant emotional impact, especially in a group setting.
Rabbits are strongly driven by their reproductive instincts, so the sudden loss of these hormones often leads to a change in behavior. Since there is no natural selection in captivity (such as predators or disease), neutering is the most responsible option. Without neutering, solitary housing or continuous breeding would not be ethical for the well-being of the rabbits.

Rabbits Are Still Fertile After Neutering!

It is crucial to separate male rabbits from sexually mature females after neutering, as there may still be some sperm in the vas deferens that can be released. The rabbit will only be infertile once the remaining sperm has died off. The exact length of time that sperm can remain viable has not been scientifically determined, but studies on guinea pigs suggest a range of 7 to 70 days, which likely applies to rabbits as well. This would mean that a quarantine period of about 10 weeks should be observed to eliminate any risk of pregnancy.
However, in practice, it has been found that a shorter period is usually sufficient. After three weeks, there have been no reported cases of pregnancy. The first three weeks are more critical, as this is when there could still be a „final shot“ of viable sperm.
The only exception is if the male rabbit was neutered before reaching sexual maturity (early neutering). In this case, there are no sperm in the vas deferens, and the neutered rabbit can be reintroduced to females immediately after the procedure.

Neutering or Sterilization?

It is often mistakenly believed that females are sterilized and males are neutered. However, the term has nothing to do with gender. Rabbits are generally neutered, regardless of their sex.

Neutering
Neutering makes the animal infertile and stops hormone production (sexual behavior, hormonal influences, heat, urine marking, etc.). In neutering, the gonads are removed (the testes in males, the ovaries in females). In an extended neutering procedure (ovariohysterectomy), the uterus is also removed.

Sterilization
Sterilization only makes the animal infertile, while hormone production continues. In sterilization, the transport of sperm or eggs is blocked by severing the vas deferens or fallopian tubes. This procedure is not recommended for rabbits, as in many cases, the vas deferens can reconnect over time.

Spaying Female Rabbits


Under extremely good living conditions (around 100 square meters of space, even at night), it is possible to keep a neutered female rabbit group with an intact male rabbit. In tighter living conditions, all males must generally be neutered, as the neutered females would be overly pressured. Females that could come into contact with intact male rabbits or wild rabbits due to free-roaming should also be spayed. The same applies to medically necessary spaying due to health issues. However, there is disagreement among rabbit lovers about preventive spaying of female rabbits.

For Preventive Spaying of Female Rabbits:

  • Rabbits are prone to uterine cancer and can develop other uterine diseases (though not with an 80% probability, as often claimed). Especially if one has experienced such cancer firsthand, prevention becomes desirable.
  • Uterine diseases are often diagnosed too late or not at all, causing rabbits to suffer unnecessarily and even die. Hardly any owners perform preventive check-ups for uterine cancer. It is painful for an owner when such a disease is diagnosed too late, and nothing can be done to help.
  • By the time cancer is discovered, it may have already metastasized, meaning the rabbit is terminally ill and must be euthanized to avoid a cruel death from suffocation.
  • Rabbits that are already ill (e.g., from other diseases) may no longer be suitable for anesthesia, making treatment difficult or impossible if a uterine disease occurs.
  • Rabbits in pet ownership do not need their uterus for reproduction.
  • Some owners even report that spaying makes rabbits more compatible with other rabbits (though this is not always the case, depending on the cause of the incompatibility).
  • In cases of uterine cancer, spaying is absolutely necessary and not controversial as a treatment.
  • Uterine diseases are, based on experience, more common in indoor rabbits than in outdoor rabbits.
  • Rabbits that could come into contact with other (wild) rabbits should be spayed to avoid unwanted offspring. For example, rabbits allowed to roam freely in areas where wild rabbits live.
  • Spaying is routine in some veterinary clinics and with some rabbit-experienced veterinarians, which significantly reduces the risk of complications. Additionally, high anesthesia standards and veterinarians specializing in small animals help reduce risk.
  • Rabbits in captivity cannot express their sexual drive properly and often suffer from an overactive sexual drive.
  • In indoor housing, spaying prevents or resolves unwanted behaviors such as urine spraying and marking. In some cases, it is impossible to keep unspayed females in free-roaming environments, as they may mark with urine. Spaying allows for freer living arrangements, thus improving quality of life.
  • Hormonal imbalances (e.g., pseudopregnancy, heat cycles) can create unrest in the group and cause significant stress for the partner rabbits due to extreme behavior. In larger groups, incompatibilities are often observed. Depending on the space available, the other rabbits may suffer greatly from this.
  • Some does suffer from severe hormonal imbalances.
  • Many veterinarians recommend preventive spaying based on their experience.
    Ultrasound and X-ray examinations cannot 100% detect uterine diseases, which can give owners a false sense of security.

Anyone who decides to have a female rabbit spayed should never have it done „just anywhere“! It is crucial to ensure that the procedure is carried out by a rabbit-experienced veterinarian with excellent anesthesia management, as the anesthesia risk can be very high otherwise!

Against Preventive Spaying of Female Rabbits

  • Just because a condition is common, it doesn’t mean the entire organ should be removed as a preventive measure (e.g., the breast in women due to breast cancer being common, or teeth in rabbits because dental diseases are frequent).
  • Many uterine changes are benign (such as cysts) and only become problematic due to their size (e.g., certain forms of endometrial hyperplasia).
  • Preventive spaying goes against animal welfare laws if it is not done to prevent reproduction and no health issues justify it (illness being the indication for spaying). The legal basis is § 6 of the Animal Protection Act (TschG), which states, „It is prohibited to completely or partially amputate body parts or to completely or partially remove or destroy organs or tissues of a vertebrate.“ The uterus is an organ that is removed in this case.
  • Spaying is a significant procedure involving opening the abdominal cavity, and it carries anesthesia risks. It is tragic if a one- or two-year-old rabbit dies during a surgery that wasn’t necessary – it might never have developed cancer, and even if it did, it could have lived a few more years before that. Depending on the specialization of the veterinarian (small animal vet) and anesthesia techniques, as well as how often the procedure is performed, the anesthesia risk can be either very high or very low.
  • In addition to the anesthesia and postoperative risks of death, spaying also carries long-term effects that are poorly researched. These include obesity and a lack of physical activity, which in turn promote other health issues (often referred to as „fat lazy rabbit syndrome“). Neutered female rabbits, due to their increased weight, are more prone to urinary sludge and stones, osteoarthritis, joint problems, and digestive disorders like constipation or bloating (due to organ displacement from fat). These risks can be minimized through proper diet and housing.
    Adhesions can form around the surgical site, leading to digestive issues, pain, and other symptoms. Reduced marking behavior may also contribute to urinary sludge.
  • Sexual drive is a natural part of a rabbit’s life, and spaying removes some of its natural instincts.
    Is it justifiable to operate on a rabbit to adapt it to human needs (e.g., to prevent urine spraying)?
    Most uterine cancers occur in older rabbits (from 4-5 years of age), although there are exceptions.
    Prevention is possible (recognizing signs of uterine diseases, regular palpation, ultrasound/X-rays if suspected). Signs include: aggression, restlessness, pain when palpating, frequent pseudopregnancies (2-3 times a year is normal, but if a doe is persistently pseudopregnant, it’s concerning), vaginal discharge, general signs of illness like lethargy, poor appetite, weight loss with a bloated abdomen or even weight gain. Please educate yourself!
  • If a rabbit becomes ill, spaying can still be performed. Contrary to common belief, anesthesia risks for older rabbits are not increased, but rather lower, unless the rabbit has other health conditions.
    Uterine cancer surgeries are often unnecessary in older rabbits, as they often die from other diseases before cancer becomes painful or life-threatening or before it displaces other organs in the abdomen.
  • A preventive spaying procedure carries an anesthesia risk (Brodbelt et al., 2008):
    One in 72 rabbits dies during or after anesthesia (including severely ill animals).
    One in 137 healthy rabbits dies during procedures like neutering.
    This anesthesia risk is particularly high if the veterinarian is not experienced with rabbits.
    Often, pet owners compare prices and choose the cheapest practice, rather than one with the safest anesthesia practices. This greatly increases anesthesia risk. A preventive spaying should only be performed in a specialized practice with very good anesthesia protocols.

Simply choosing not to spay a female rabbit is not a solution. Those who decide against spaying should have the rabbit thoroughly examined (at least twice a year) by a rabbit-savvy veterinarian, including possible ultrasound exams. If any issues are found, the rabbit should be spayed. Preventive check-ups may be time-consuming and involve costs.

Spaying is not just spaying!

According to current scientific knowledge, both the ovaries (ovariectomy) and the uterus should generally be removed during the procedure (ovariohysterectomy) in rabbits. An exception may be very young rabbits between six and eight months old with a healthy uterus. Why is this the case? The uterus can still develop diseases even after spaying, which means the goal of the spaying procedure might not be fully achieved.

WARNING: Many veterinarians who are not experienced with rabbits only remove the ovaries, which is much less invasive and therefore cheaper. Always go to a rabbit-savvy veterinarian for spaying. They have better anesthesia management, and as a result, the anesthesia risk is generally much lower. The seemingly „cheap price“ is usually due to poorer anesthesia management and leaving the uterus intact. In the end, you end up paying more for much less, and in the worst-case scenario, your rabbit may pay with its life! Spaying is not a standard procedure; the differences in how it is performed and the anesthesia management are huge!

Alternatives to Spaying Female Rabbits

Rabbits can be chemically castrated using a hormone implant (Deslorelin, brand name: Suprelorin). This bypasses the anesthesia risk. It is important to only chemically castrate rabbits that do not have any uterine changes! An ultrasound should be done beforehand. Over the course of a rabbit’s life, chemical castration is slightly more expensive than traditional spaying, but it can be reversed at any time. This can be useful, for example, if you’re trying to determine whether behavioral issues are hormonally driven. Scientific sources for your veterinarian (some pet-savvy veterinarians are already using chemical castration very successfully):

– Geyer, A., Poth, T., Otzdorff, C., Daub, L., Reese, S., Braun, J., & Walter, B. (2016). Histopathologic examination of the genital tract in rabbits treated once or twice with a slow-release deslorelin implant for reversible suppression of ovarian function. Theriogenology, 86(9), 2281-2289.
– Phungviwatnikul, T., Tisyangkul, V., Pagdepanichkit, S., & Sirivaidyapong, S. (2011). Effect of GnRH-agonist deslorelin subcutaneously implantation on fertility in mixed breed female rabbits at the age of 2.5 months and 5 months. The Thai Journal of Veterinary Medicine, 41, 179.

How Many Rabbits Actually Get Uterine Cancer?

Unfortunately, numbers continue to circulate that claim an alarmingly high rate of uterine cancer in pet rabbits, often citing 80%. However, such high rates have only been observed in specific breeding lines. It’s important to note that the occurrence of uterine cancer varies depending on the line. Most studies suggest that only 0-20% of female rabbits are affected by uterine cancer. These results align with our experiences, showing that uterine cancer is a relatively common condition but certainly not affecting 80% of rabbits. The anesthesia risk, or the risk of dying during or after surgery, is unfortunately still quite high (depending on anesthesia technique and the vet’s specialization), and in some cases, it may be similar to the risk of uterine cancer itself. Only highly specialized rabbit veterinarians with excellent anesthesia techniques can significantly reduce this risk. A spaying procedure should always be carried out with excellent anesthesia management; if such a practice is unavailable, other options might be more suitable.

Risks of Spaying (Female) Rabbits

Unfortunately, the consequences of spaying female rabbits have not been comprehensively studied so far. While there was a time when the trend was to spay pets in general, there is a growing shift away from this trend nowadays, not only in rabbits but also in other pets.

Anesthesia Risks (see Brodbelt et al. 2008):

One out of 72 rabbits dies during or after anesthesia (including those with serious illnesses).
One out of 137 healthy rabbits dies during procedures such as spaying.


Post-Operative Complications:

Wound healing problems, complications after surgery, adhesions at the incision site, and hernias.


Weight Gain Post-Spaying:

Weight gain is common after spaying, which can lead to numerous follow-up health issues, such as arthritis and bladder sludge.


Incontinence:

In very rare cases, rabbits may lose control of urination after spaying, which can lead to urinary tract infections and stone formation.


Osteoporosis:

Spayed rabbits may develop brittle bones and teeth due to hormonal changes, which can make them more prone to fractures.

Our Recommendation:

Every rabbit owner should thoroughly explore this topic to form their own opinion. It is also very important to be aware of the signs of uterine diseases and to act quickly when they appear. Depending on the housing situation, rabbits are not always under constant observation and may simply be fed and provided for, which can cause illnesses to go unnoticed. For these animals, we recommend considering preventive spaying. This is also advisable if a rabbit is significantly stressed due to frequent heat cycles or false pregnancies. If signs occur that suggest a uterine disease, we recommend having the rabbit medically examined and potentially spayed. If you have a rabbit-savvy vet with excellent anesthesia management who routinely performs female spaying, preventive spaying is a viable option.

Signs of Uterine Disease:

Aggression, restlessness, pain when palpating, frequent false pregnancies (up to 2 or 3 times a year is normal, but if a female is persistently pseudopregnant, it is concerning), vaginal discharge, general signs of illness such as lethargy, poor appetite, weight loss with a relatively bloated abdomen or even weight gain. Blood or mucus discharge from the vagina can also be indicators.

Prevention

Regardless of the method you choose for your rabbits, it is crucial to be aware of the risk of uterine diseases in female rabbits and recognize the signs. A form of prevention should always be selected:

  • Preventive Spaying with a pet-savvy vet who has good anesthesia techniques (see here). This is especially important for rabbits that are not under close observation, inexperienced owners, or owners who are reluctant to take preventive measures. Can be performed from around the sixth month of life.
  • Hormone Chip: Implanting the Suprelorin chip in very young rabbits (before they become hormonally active or if the uterus shows no changes – ultrasound check before implanting). The chip needs to be replaced regularly, and over the years, it is more expensive and demanding than spaying.
  • Biannual Palpation During Vaccination (by a pet-savvy vet!). If the uterus is palpable, perform an ultrasound to check for uterine disease and consider spaying. You should be familiar with the signs of uterine diseases and keep an eye on them! Preventive annual/semi-annual ultrasounds are advisable.