by Guen Bradbury

1.1 Introduction

Rabbits are highly social animals and require housing with other rabbits (Love, 1994), but rabbits are still frequently kept alone (PDSA, 2019). One major barrier to keeping rabbits in pairs is that it can be hard to introduce rabbits to each other. Rabbits are highly territorial and will defend their territory against perceived intruders (Crowell-Davis, 2007). To achieve a successful, stable relationship between two rabbits that are introduced to each other (i.e. do not grow up together) requires that they are ‘bonded’ – they are introduced in a way that allows them to establish a stable hierarchy without injuring each other. Rabbits bonded to other rabbits show less markers of stress and more affiliative behaviours than those introduced to new rabbits (Chu, 2004; Noller, 2013).

It is widely accepted that certain combinations of rabbits form ‘better’ bonds than others, but the evidence for this is limited. The Rabbit Welfare Association & Fund (RWAF) wanted to ensure that its recommendations (Firth, RWAF) were targeted to ensure the best chance of a good quality of life for the largest number of rabbits. Therefore, it needed to understand how owners, veterinary professionals, and leaders of rabbit rescue centres perceived bond formation and bond breakdown.

There are various ways to define whether or not a rabbit ‘bond’ is successful. For this study, we focused on the start and end of a bond – what increases the chance of a successful initial bonding process and what increases the risk of bond breakdown. We wanted to understand the perspectives of owners (who mostly see ongoing bonds between rabbits), rescue centres (which mostly see the initial bond formation), and veterinary professionals (who mostly see the injury caused by bond breakdown).

1.2 Methods

In February and March 2020, we sent out three online questionnaires via Survey Monkey. These were distributed through RWAF’s online mailing lists. We received 1218 unique owner responses, 82 veterinary professional responses, and 22 responses from rescue centres.

The questions posed are listed in the Appendix.

1.3 Results

1.3.1 Owner survey

We received 1218 responses from rabbit owners, who between them had owned over 3000 pairs of rabbits (if one rabbit has had several companions, then each combination would count as a separate pair).

We asked if owners had tried to bond rabbits themselves, and whether they had succeeded or failed with different sex pairings. Owners described 3735 attempted pairings, of which 65% were male–female (2396/3735), 15% (566/3735) were groups, and 10% each were female–female (391/3735) and male–male (382/3735). For male–female pairings, owners reported 2396 attempts, of which 95% (2278/2396) were successful. For groups of three or more rabbits, owners reported 566 attempts, of which 84% (474/566) were successful. For female–female pairings, owners reported 391 attempts, of which 89% (346/391) were successful. For male–male pairings, owners reported 382 attempts, of which 86% (330/382) were successful.

We asked whether the owners had ever had a pair of rabbits that fought so badly that they could no longer keep the rabbits together. 40% of owners reported that this had happened (486/1218). In total, 753 rabbit combinations were reported to have irretrievably broken down, of which 25% (191/753) were male–male pairs, 21% (158/753) were female–female pairs, 30% (224/753) were male–female pairs, and 24% (180/753) were groups.  We did not ask the owners explicitly how many male-male pairs, male-female pairs and female-female pairs they had owned. However, we can use the above data on attempted bond pairings to scale these figures. We can assume that the population of rabbit pairs owned is broadly similar to the population of rabbit pairs that owners attempted to bond (there will be similar considerations of owners keeping rabbits together and owners attempting to bond rabbits together). Using the attempted bond data, we would assume that of the total population of rabbit relationships, 65% are male–female, 15% are groups, and 10% each are female–female and male–male.

We can compare other bond breakdowns to the baseline of breakdowns in male–female pairs (scaled by the frequency of these bonds in the general pet rabbit population – 65% male–female pairs, 15% groups, and 10% male–male and female­–female):

  • groups break down 3.5 times more
  • female–female pairs break down 4.6 times more
  • male–male pairs break down 5.4 times more

In the combinations of rabbits that fought and needed to be separated, the owners reported that the rabbits in 67% of cases were both neutered and in 19% were both unneutered. Of the remainder, only the male was neutered in 5% of cases and just the female in 1% – as all of these rabbits must have been in male–female pairs, it suggests that in 17% of bond breakdowns in male–female pairs, only one of the rabbits was neutered. Of the rabbits that fought, the majority were described to have an adequate environment – only 8% were reported to live in a hutch in the garden or a cage in the house. Reasons given for bond breakdown included illness or separation (32%, 52/165), puberty (19%, 32/165), introduction of new rabbits (18%, 29/165), spring hormones (9%, 15/165), or lack of neutering (8%, 13/165).

We asked owners if there was anything else they wanted to tell us about bonding. Some owners reported finding the process surprisingly easy, “Great experience on this occasion,” “Never had a problem”, and “It was so easy I didn’t even realise it was supposed to be so hard to do.” Many owners said that it was “stressful,” that it was “horrible, but so worth it,” or “Traumatic for both rabbits and us as a family”. One owner reported living with a mesh fence across their lounge for eighteen months until the rabbits were bonded. The most common pieces of advice were about using a neutral space, about scent-swapping and separating the rabbits but allowing nose-to-nose contact, and about taking time and doing it slowly. Owners also believed that neutering their rabbits and seeking professional help was important. Other themes that came up frequently were around only separating bonding rabbits if they were actually fighting, providing plenty of space (though a smaller number of owners suggested the opposite), avoiding male–male pairs, and matching rabbits on personality. A small number of owners suggested stress bonding. Owners struggled because “the information online and in textbooks is so limited,” and said “it would be helpful having online videos of good and bad bonds.” Two responses suggested smearing banana on the rabbits’ foreheads and two suggested using Pet Remedy.

1.3.2 Veterinary professional survey

We received 82 responses from veterinary surgeons or veterinary nurses, who between them had seen over 1500 rabbits in their practices in the previous year.

We asked about rabbits brought in because they were fighting with their companion (s). There were 203 reports of this happening, of which 116 (57%) were male–male pairs, 56 (28%) were female–female pairs, 21 (10%) were male–female pairs, and 10 (5%) were groups.

We can compare other bonds to the baseline of male–female pairs (scaled by the frequency of these bonds in the general pet rabbit population – 65% male–female pairs, 15% groups, and 10% male–male and female­–female):

  • group breakdown requires veterinary attention 2.2 times more
  • female–female pair breakdown requires veterinary attention 6.5 times more
  • male–male pair breakdown requires veterinary attention 37 times more

We asked why these bonds had broken down and the veterinary professionals gave 93 reasons. Most commonly cited were lack of neutering (28, 30%), young rabbits reaching puberty (25, 27%, often male–male pairs), and inadequate or restricted environment (16, 17%). Other reasons given were separation or illness (12, 13%) and poor or rushed bonding (9, 10%).

We asked whether the veterinary professionals had ever had to euthanise a rabbit because of injuries sustained during a fight with a companion – 12% (10/82) reported this had happened. In 7 cases, these involved male-male pairings – 5 of which involved irreparable injuries to the urethra, penis, or scrotum and testicles. Female–female pairs were reported in 2 cases of injury requiring euthanasia.

We conducted a separate analysis of all 139 of the questionnaires submitted to RWAF in the applications for rabbit-friendly practice status. We recorded what age the practice recommended neutering for male and female rabbits. 23% of practices (32/139) recommended castrating male rabbits at or before 12 weeks of age and 79% (104/139) practices recommended spaying female rabbits at or before 20 weeks of age.

1.3.3 Rescue centre survey

We received 22 responses from people working at rescue centres, who between them had rehomed over 2500 rabbits in the previous year.

We asked about rabbit pairs in which one or both rabbits had been given up for rehoming because of bond breakdown. There were 94 reports of bond breakdowns, of which 48 (51%) were male–male pairs, 35 (37%) were female–female pairs, 4 (4%) were male–female pairs, and 7 (7%) were groups of three or more rabbits (the sex pairing couldn’t be recalled in 6 cases).

We can compare other bond breakdowns to the baseline of breakdowns in male–female pairs (scaled by the frequency of these bonds in the general pet rabbit population – 65% male–female pairs, 15% groups, and 10% male–male and female­–female):

  • groups were rehomed 7.6 times more
  • female–female pairs were rehomed 57 times more
  • male–male pairs were rehomed 83 times more

We asked about the main reason that rabbits start fighting. The most commonly cited reasons were lack of neutering (30%), separation or inadequate environment (17%), and unneutered male rabbits reaching puberty (13%). Other reasons given were unneutered male–male or female–female pairs being kept in close proximity to other rabbits, environmental change, or illness in one of the rabbits.

We asked the rescue centres to rank how easy different combinations of rabbits were to bond. 76% of rescue centres said that male–female pairs were easiest to bond (weighted average score of 1.48, where 1 is easiest to bond and 5 is hardest to bond). The other three combinations (male–male, female–female, group) had weighted averages of 3, 3, and 3.4 respectively. 76% of rescue centres said that they would only bond neutered rabbits. 20% said that they would try a neutered male and an unneutered female if there was good reason to do so (the female had health problems that would increase the risk of surgery; the female’s neuter status was unknown; the owners were too anxious about the surgical risk to their current female).

Most commonly, rescue centres reported that they considered owner choice and temperament of rabbits when choosing which rabbits to attempt to bond (both 10/22). Other aspects considered were size of the rabbits, breeds of the rabbits, and ages of the rabbits.

To assess whether a bond would be successful, most rescue centre staff would look for the rabbits spending time close to each other (eating or resting), performing mutal grooming behaviours, and without fighting. We asked what they would advise rabbit owners about rabbit bonding – common themes were to ensure the rabbits were neutered, to bond them in a neutral area (often with a divide initially) and to give the rabbits plenty of time to get to know each other. Many recommended against ‘speed-dating,’ confinement, or other high-stress ways to try to ‘bond’ rabbits.

1.4 Discussion

The results of this survey suggest that male–female pairs are easiest to bond successfully and may be less likely to have that bond breakdown. This is in line with the current guidelines from RWAF.

Bond selection

The majority of the survey results from rescue centres and owners reported that male–female pairs of rabbits were easiest to bond. This is in line with the established wisdom. In the wild, rabbits typically live in male–female pairs. Even when rabbits are neutered, they still show sex-specific behaviours because the behaviour is not just driven by the gonadal hormones. The drives for different resources differ between male and female rabbits, so there is likely to be less competition. This means that, even if both rabbits are neutered, the residual sex-specific behaviours are more likely to be compatible for long-term pairs between rabbits of the opposite sex.

Most rescue centres stressed the importance of neutering both rabbits before attempting a bond. Although 20% said they would try a bond where one rabbit was unneutered, they had very pragmatic reasons for doing so – if the female had health problems that posed increased surgical risk, if the female’s neuter status was unknown, or if the female’s owners were too anxious about surgery. Given the well-documented risks of anaesthesia in rabbits in general practice, having a policy for exceptions seems reasonable.

Rescue centres most often picked a suitable opposite-sex rescue rabbit for bonding to an owned rabbit based on the owner’s preferences, though they did also consider temperament. This additionally suggests that the bonding success rate is largely determined by correct environment and introductions, rather than very specific compatibility characteristics.

Bond formation

Rescue centres assessed likelihood of bonding success by looking for the rabbits spending time in proximity to each other, showing mutual grooming, and not fighting. Respondents said they would advise owners to neuter their rabbits, to bond them in a neutral area (often with a divide initially) and to give the rabbits plenty of time to get to know each other. Many recommended against ‘speed-dating,’ confinement, or other high-stress ways to try to ‘bond’ rabbits.

Owners reported a wide variety of experiences when trying to bond their rabbits – this may reflect different set-ups, different expectations, or substantial variation in the ease of different rabbits to form successful relationships. In general, it appeared that the majority of owners were favouring a slow-bonding approach with neutered animals and professional help, which is in line with current RWAF advice on good practice to ensure the animals’ welfare. Many owners didn’t feel well informed about positive and negative bonding behaviours – perhaps this is an area at which new campaigns or material could be targeted. Given that so many bonds break down at home and given that so many owners are trying to bond their rabbits themselves, it’s important that rabbit owners have access to reliable material to increase the likelihood of good outcomes.

Bond breakdown

It is surprising that 40% of owners report a pair of rabbits that fought so badly that they had had to separate them. The majority of these pairs (67%) were both neutered and lived in an adequate environment. The major triggers for bond breakdown were illness or separation, puberty, and introduction of new rabbits. This suggests the importance of advising owners and veterinary professionals on how to keep rabbits together during illness, veterinary visits, and hospitalization wherever possible.

Data from all surveys suggest that male–female pairs are more stable than any other pairing or group, and that groups of rabbits are more stable than either single-sex pairing. While we did not explicitly ask how many male-male pairs, male-female pairs and female-female pairs they had owned (an omission, in hindsight), we believe that the representation of each pair and group in the bonds attempted by the survey respondents can act as a reasonable approximation for the incidence in the overall population.

A large proportion of owners report that a bonded pair of young rabbits (usually male–male) started fighting at puberty. Rabbit breeders often keep young female rabbits to breed from, which means that there will always be more pet male rabbits than pet female ones. This poses a welfare dilemma – how to keep male rabbits in pairs without causing bond breakdown. There could be different solutions – prepubertal neutering (though this has poor public perception), post-neutering bonding at rescue centres (though this requires solitary housing prior to puberty), or no longer selling pre-pubertal male–male pairs. Additionally, advising against female–female pairs would avoid worsening the discrepancy and would increase the number of stable male–female pairings possible.

From the additional analysis of when practices advised neutering of young rabbits, it was clear that many practices did not recommend neutering male rabbits as early as RWAF suggests. RWAF recommends castrating rabbits at 10-12 weeks or as soon as the testicles descend, but only 23% of practices (32/139) recommended this. Waiting longer than three months increases the risk that young male rabbits will fight, and once they fight, neutering rarely allows them to be reintroduced. RWAF recommends that female rabbits are spayed at 16–20 weeks of age, and 79% (104/139) practices recommended spaying female rabbits at or before 20 weeks of age. The practices submitting these data are self-selected for an interest in rabbit medicine, and it is likely that less-engaged practices may recommend similar ages for neutering for rabbits, cats, and dogs (typically 4–6 months). Therefore encouraging practices to neuter male rabbits early might have substantial welfare benefits.

From the veterinary professional survey, it was clear that some fights caused very severe injuries. Vets were most likely to see owners of fighting male-male rabbit pairs, then female­–female pairs, then male–female pairs. This is in contrast to the bond breakdowns reported by owners. It is possible that this reflects an increased severity in fights between two male rabbits or an increased risk of injury when males were involved. The external genitalia of male rabbits is much more likely to be injured than that of females, and injuries involving the urethra are extremely difficult to repair. Injuries to males from females often occur when the male mounts the female rabbit’s head and has its external genitalia bitten. Injuries to males from males often occur when one rabbit lies on its back and kicks out – this can cause scrotal or penile injury or even evisceration.  Vets perceived that lack of neutering and rabbits reaching puberty were significant causes of bond breakdown – this may reflect the fact that they primarily saw male–male pairs. It was notable that all of the reported fatal fights involved single-sex pairings, where described – primarily male–male pairings.

In general, rescue staff and veterinary professionals reported similar causes of bond breakdowns. This supports the hypothesis that rescue centre staff and veterinary professionals may see the worst breakdowns, which occur in single-sex pairs. This may explain the discrepancy between the likelihood of bond breakdown in different pairs as reported by owners as compared to those reported by rescue centres. For both groups, it appears that male–female pairs are significantly more stable than any other pairings, and that it is very significantly less likely that a rabbit will require rehoming after bond breakdown if it is in a male–female pair.

In general, it seemed that groups were harder to bond and less stable than male–female pairs. This is likely to be because within a pair, there are two relationships (each rabbit’s relationship with its partner). Within a group of three, there are six relationships. If each relationship has a set probability of breaking down, then the more relationships there are, the more likely there is to be a breakdown. However, the data from both owners and rescue centres suggests that groups of rabbits seem less likely to break down than single-sex pairs (which is somewhat surprising, given that within any group, there will be at least two animals of the same sex). The network of relationships between a group of rabbits may help to reduce the stress between a certain pair of rabbits because they can interact with others – perhaps, if the pair of rabbits were kept without others, the bond might break down.

Conclusion

In conclusion, these results support current guidelines that male–female pairs are easier to bond successfully and seem less likely to cause each other injury if the bond breaks down. For better success in male–male pairs, neuter both rabbits at 10–12 weeks or as soon as the testicles descend. Veterinary practices should avoid separation of bonded pairs during consultations or hospitalization to reduce the risk of bond breakdown.

1.5 References

Love, James A. “Group housing: meeting the physical and social needs of the laboratory rabbit.” Laboratory Animal Science 44.1 (1994): 5.

PDSA. “PDSA Animal Wellbeing (PAW) Report 2018.” (2018).

Crowell-Davis, Sharon L. “Behavior problems in pet rabbits.” Journal of exotic pet medicine 16.1 (2007): 38-44.

Firth, Fiona. “The RWAF Guide to pairing up rabbits”

Noller, Crystal M., et al. “The influence of social environment on endocrine, cardiovascular and tissue responses in the rabbit.” International journal of psychophysiology 88.3 (2013): 282-288.

Chu, Ling-ru, Joseph P. Garner, and Joy A. Mench. “A behavioral comparison of New Zealand White rabbits (Oryctolagus cuniculus) housed individually or in pairs in conventional laboratory cages.” Applied Animal Behaviour Science 85.1-2 (2004): 121-139.

1.6 Appendix

Rescue Centres

How many rabbits have been rehomed through your centre in the last year?

If you think back to rabbits that were brought in for rehoming because they were fighting with their companion (s), how many pairs were:

  1. Male-male pairings
  2. Female-female pairings
  3. Male-female pairings
  4. Groups of three or more rabbits
  5. Don’t know or can’t remember

What do you think are the main reasons that bonded pairs start fighting?


Please rank these combinations of rabbits by how easy you find it to bond them (where 1 is easy)

  1. Male-male pairings
  2. Female-female pairings
  3. Male-female pairings
  4. Groups of three or more rabbits

How do you select which rabbits to try to bond together?

When do you know if a bond will be successful? What signs do you look for?

What would you advise owners who are trying to bond rabbits?

Vets/ vet nurses

On average, how many rabbits do you see in your practice a week?

Think back to rabbits that were brought in because they were fighting with their companion(s). How many pairs were:

  1. Male-male pairings
  2. Female-female pairings
  3. Male-female pairings
  4. Groups of three or more rabbits
  5. Don’t know or can’t remember

What do you see as the main reasons that rabbits start fighting with their companion (s)?

Have you ever had to euthanise a rabbit because of injuries sustained during a fight with a companion? 

  1. Yes
  2. No

[comment box]

Owners:

How many pairs of rabbits have you owned (if you’ve had one rabbit who has had several companions, then count each time it was in a different pair)

Have you ever had a pair of rabbits that fought so badly that you could no longer keep them together?

If yes, please write the number of pairs that this has happened to

  1. Male-male pairings
  2. Female-female pairings
  3. Male-female pairings
  4. Groups of three or more rabbits
  5. Can’t say

Were these rabbits neutered?

  1. Yes – both
  2. Yes- male
  3. Yes – female
  4. No

Pick the option that best described where they spent most of their time

  1. Free run of my home
  2. In a cage in my home
  3. In a hutch in my garden
  4. In a hutch with attached run in my garden

Do you know what caused them to start fighting?

[open text box]

Have you ever tried to bond rabbits yourself? Please indicate how many pairs were successful and how many unsuccessful.

  1. Male-male
  2. Female-female 
  3. Male-female 
  4. Groups of three or more rabbits